Subcortical projections to the lateral geniculate body in the rat

Summary The subcortical projections to the lateral geniculate body (LGB) in the rat were studied by means of discrete HRP iontophoretic deposits in the dorsal or the ventral LGB; the labelling was compared to that resulting from HRP deposits in neighboring nuclei.After injecting HRP in the dorsal LGB, labelled cells appeared bilaterally in the ventral LGB, pretectum, superior colliculus, lateral groups of the dorsal raphe nucleus and locus coeruleus. Ipsilaterally, labelled cells were found in the lateral posterior thalamus, nucleus of the posterior commissure and deep mesencephalic reticular nucleus.After injecting HRP into the ventral LGB, labelled cells were observed bilaterally in the pretectum, superior colliculus and dorsal raphe nucleus (lateral groups). Contralateral labelling appeared in the ventral LGB and parabigeminal nucleus. Ipsilateral labelling was found in the zona incerta, lateral posterior thalamus, lateral and medial mesencephalic reticular formation, vestibular and dorsal tegmental nuclei.These findings provide evidence of subcortical projections to the LGB arising in visually-related areas as well as extravisual areas, which might be related to the LGB boutons that survive complete cortical and retinal ablations.     

Effects of subcortical ablations on cortical association responses in the cat

The effects of subcortical lesions on cortical polysensory association area responses to peripheral sensory and direct reticular stimulation were investigated in acute chloralosed cats. Large lesions of the mesencephalic reticular formation were followed by a reduction in the amplitude of polysensory association responses to approximately 0–20% of control levels, with little or no reduction of evoked potentials in the primary sensory cortical areas. Unilateral lesions of posterior medial thalamus or the rostral pole of the thalamus had similar effects of polysensory cortical association responses, and also abolished cortical association area responses to direct electrical stimulation of the mesencephalic reticular formation, but only in the ipsilateral cortex. More ventral lesions, in the subthalamic region, reduced nonspecific evoked responses of orbital cortex to both peripheral and reticular stimulation without impairing responses in dorsal cortical association areas. The results are discussed with regard to the pathways of sensory input to the cortical association responses areas.     

Electrophysiological study of reticulo-limbic interrelationships during prolonged action of vibration

Phasic changes in the bioelectrical activity of the dorsal hippocampus (field CA₃), the mesencephalic reticular formation, and several regions of the neocortex and the reticulo-cortical evoked potentials were measured under conditions of the action of prolonged vibration (3 months) in electrophysiological experiments with rabbits. Daily three-hour vibration during the first month of the experiment evoked an activation reaction in the EEG, characterized by a desynchronization effect in the neocortex and hippocampus and by the stabilization of thev rhythm in the mesencephalic eticular formation. Noted against this background was a certain facilitation in the reticulo-cortical evoked potentials, more pronounced in the neocortex, and a decline in the ascending activational influence of the mesenecphalic reticular formation. The three-month action of vibration exerted an inhibitory influence on reticulo-cortical interrelationships, expressed in a decline in the compound bioelectrical activity of the cortex and subcortical formations, the excitability of the mesencephalic reticular formation, and the suppression of reticulo-cortical evoked potentials. At the same time an elongation of the latent periods of the positive phases of the evoked potentials, a decline in their amplitude, and a reduction of the negative phase in limbic structures was noted. The question of the physiological mechanism of development of vibrational pathology is discussed.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 73, No. 1, pp. 20–27, January, 1987.     

Descending pathways mediating disynaptic excitation of dorsal neck motoneurones in the cat: brain stem relay.

The location of intercalated neurones mediating disynaptic excitation from tectum, tegmentum and pyramids to dorsal neck motoneurones has been investigated by: (a) recording field potentials in the lower brain stem evoked from the above systems, (b) systematic stimulation in the brain stem during intracellular recording from motoneurones innervating the splenius, biventer cervicis and complexus muscles, and (c) comparing the effects of lesions of the brain stem with kainic acid on the disynaptic EPSPs elicited from the above three systems. Electrical stimulation of the contralateral superior colliculus evoked monosynaptic field potentials which were largest in the caudal pontine reticular formation rostral to the abducens nucleus and in the rostral part of the medullary reticular formation caudal to the abducens nucleus. Likewise, stimulation of the ipsilateral tegmentum (the cuneiform and subcuneiform nucleus) evoked field potentials which were large in the caudal medulla and small in the pons. In contrast, stimulation of the contralateral tegmentum was ineffective in evoking field potentials. Stimulation of the pyramid 2-3 mm rostral to the obex elicited monosynaptic field potentials in the reticular formation of the lower brain stem that were only about 25% of those from the superior colliculus. In contrast to the field potentials from the superior colliculus, the pyramidal ones were large in the medulla and small in the pons. Lesions of the reticular formation in the lower brain stem by unilateral kainic acid injection caused disappearance of disynaptic EPSPs in motoneurones from the above three systems. These results strongly suggest that the intercalated neurones mediating pyramidal, tectal and tegmental EPSPs are reticulospinal neurones in the lower brain stem. Systematic stimulation in various locations of the lower brain stem showed that monosynaptic EPSPs were evoked from the regions of the reticular formation which received projection from the above three descending systems. The effective regions for evoking the EPSPs in splenius (SPL) were located somewhat more dorsally than for biventer cervicis and complexus (BCC) motoneurones. The descending axons of presumed reticulospinal neurones were stimulated with electrodes placed in medial, middle and lateral positions at the spinomedullary junction. Monosynaptic EPSPs in SPL and BCC motoneurones were evoked from the medial and middle electrodes but not from the lateral electrode.     

Effects of kainic acid lesions of the nucleus reticularis tegmenti pontis on fast and slow phases of vestibulo-ocular and optokinetic reflexes in the pigmented rat

Summary The nucleus reticularis tegmenti pontis (NRTP) and adjacent pontine reticular formation were lesioned chemically using the neurotoxic agent kainic acid, and the effects of these lesions on horizontal ocular optokinetic and vestibular nystagmus were examined. Eye position was measured in the alert, NRTP-lesioned animals with the electromagnetic search coil technique. Optokinetic and vestibular stimuli consisted of steps of rotations or sinusoidal oscillations of a fullfield visual pattern surrounding the animal or of the animal in total darkness, respectively. In a first group of animals, small unilateral NRTP lesions were produced by placing a single kainic acid injection in the area of the left NRTP. In one third of the animals, ipsilateral quick phases of optokinetic and vestibular nystagmus were abolished. In the remaining animals, quick phases were deficient to various degrees or not affected at all. There were no changes in the characteristics of optokinetic step responses to ipsilateral pattern rotations which activate predominantly optokinetic pathways on the side of the brainstem lesion. In animals with ipsiversive quick phase deficits, contralateral pattern rotations elicited tonic eye deviations. In a second group of animals, large uni- or bilateral lesions were produced by injecting kainic acid into three separate rostral, middle and caudal levels of the right NRTP. These animals had uni- or bilateral quick phase deficits during optokinetic and vestibular nystagmus. Optokinetic nystagmus in response to velocity steps of pattern rotation towards the lesion side was strongly reduced in gain even in those animals that had no apparent deficits in the fast contraversive reset phases. In four out of six animals, responses to sinusoidal optokinetic pattern oscillations were reduced in gain and showed increased phase lags compared to controls. Vestibulo-ocular responses to velocity steps of head rotations were of normal gain but reduced in duration (measured from onset of stimulation to reversal of nystagmus). Sinusoidal vestibulo-ocular responses evoked by head oscillations exhibited reduced gain values and strongly increased phase leads in the frequency range below 0.5 Hz. The vestibular time constant was found to be around 4.5 s in animals with NRTP lesions compared to about 7.5 s in control animals. The present results show that large kainic acid lesions of the NRTP (and adjacent area) do not abolish optokinetic eye movements in the rat, in contrast to what has been reported after electrolytic lesions. The data suggest, however, that there is a failure of slow build-up of OKN slow phase velocity as well as a shortening of the vestibular time constant which correlates with the kainic acid lesions extending into rostromedial and caudal parts of the NRTP. The implications of these findings with respect to an involvement of these structures in velocity storage are discussed.Abbreviations CN cochlear nucleus - DpSC decussation, peduncle, superior, cerebellar - ip interpeduncular nucleus - MLF medial longitudinal fasciculus - NOT nucleus of optic tract - NRTPc nucleus reticularis tegmenti pontis, central subdivision - NRTPp nucleus reticularis tegmenti pontis, pericentral subdivision - p pontine nuclei - ph praepositus hypoglossi nucleus - pMC peduncle, middle cerebellar - pSC peduncle, superior cerebellar - Pyr pyramidal tract - Rcs raphe central superior - Rm raphe magnus - rpc reticular nucleus, pontine, caudal - rpo reticular nucleus, pontine, oral - TB trapezoid body - tM trapezoid nucleus, medial - tGd tegmental nucleus of von Gudden, dorsal - tGv tegmental nucleus of von Gudden, ventral - 5 trigeminal tract or trigeminal nerve - 5m mesencephalic trigeminal nucleus - 5mt motor trigeminal nucleus - 6n abducens nucleus - 7 facial nerve Prof. W. Precht died on March 12, 1985     

Effect of kainic acid injected into raphe dorsal nucleus on sleep stages in cats.

Early (up to 5 h) and late (up to 65 days) effects of kainic acid (KA) injected into raphe dorsal nucleus (NRD) at two doses, 4 and 12 nmol, on waking-sleep stages in cats were studied. Slow-wave sleep (SWS-1 and SWS-2) and rapid eye movement sleep (REM) were strongly reduced or even completely suppressed, while waking stage, especially quiet waking stage (W-2), was significantly increased during the first 5 h after the injection. The effect was much more pronounced after injection of KA at a dose of 12 nmol. These changes in sleep stages gradually subsided and starting from the first-third day up to the 65th day after injection of KA, sleep was completely normal. The effects were interpreted as reflecting the action of KA first as a strong excitant--when a suppression of sleep was established, and then as a toxic substance with respect to NRD cells--when sleep restored to normal. These results suggest that raphe dorsal nucleus is not essential for triggering or maintenance of sleep.     

A new intrathalamic pathway linking modality-related nuclei in the dorsal thalamus

Transmission of sensory information through the dorsal thalamus involves two types of modality-related nuclei, first order and higher order, between which there are thought to be no intrathalamic interactions. We now show that within the somatosensory thalamus, cells in one nucleus, the ventrobasal complex, can influence activity in another nucleus, the medial division of the posterior complex. Stimulation of ventrobasal complex cells evoked inhibitory postsynaptic currents in cells of the medial division of the posterior complex. These currents exhibited the reversal potential and pharmacology of a GABAA receptor-mediated chloride conductance, indicating that they result from the activation of a disynaptic pathway involving the GABAergic cells of the thalamic reticular nucleus. These findings provide the first direct evidence for intrathalamic interactions between dorsal thalamic nuclei.     

大鼠终纹床核卵圆核及其邻近区域的传出纤维联系——WGA-HRP顺行追踪法研究

本实验选用150～260g的雄性Sprague-Dawley大鼠13只,把WGA-HRP/HRP混合水溶液加压注入一侧终纹床核群前外侧区的卵圆核区域,冰冻切片,TMB法呈色后,在中枢看到顺行标记终末最密集的部位是:下丘脑后部外侧区、中央杏仁核、中脑中央灰质、臂旁核、三叉神经中脑核、蓝斑;比较多的部位是视前区、下丘脑室周区、弓状核、丘脑中线核群、内侧纽核、腹侧背盖核、脚桥背盖核、中脑网状结构、中缝背核以及迷走神经复合体;在线形中缝核、中央上核、腹侧背盖区、黑质,以及延髓中介核,也看到少量标记终末。本工作对卵圆核的传出纤维联系,进行了较全面的观察。     

An autoradiographic analysis of ascending projections from the medullary reticular formation in the rat

Ascending projections from the several nuclei of the medullary reticular formation were examined using the autoradiographic method. The majority of fibers labeled after injections of [3H]leucine into nucleus gigantocellularis ascended within Forel's tractus fasciculorum tegmenti which is located ventrolateral to the medial longitudinal fasciculus. Nucleus gigantocellularis injections produced heavy labeling in the pontomesencephalic reticular formation, the intermediate layers of the superior colliculus, the pontine and midbrain central gray, the anterior pretectal nucleus, the ventral midbrain tegmentum including the retrorubral area, the centromedian-parafascicular complex, the fields of Forel/zona incerta, the rostral intralaminar nuclei and the lateral hypothalamic area. Nucleus gigantocellularis projections to the rostral forebrain were sparse. Labeled fibers from nucleus reticularis ventralis, like those from nucleus gigantocellularis, ascended largely in the tracts of Forel and distributed to the pontomedullary reticular core, the facial and trigeminal motor nuclei, the pontine nuclei and the dorsolateral pontine tegmentum including the locus coeruleus and the parabrachial complex. Although projections from nucleus reticularis ventralis diminished significantly rostral to the pons, labeling was still demonstrable in several mesodiencephalic nuclei including the cuneiform-pedunculopontine area, the mesencephalic gray, the superior colliculus, the anterior pretectal nucleus, the zona incerta and the paraventricular and intralaminar thalamic nuclei. The main bundle of fibers labeled by nucleus gigantocellularis-pars alpha injections ascended ventromedially through the brainstem, just dorsal to the pyramidal tracts, and joined Forel's tegmental tract in the midbrain. With the brainstem, labeled fibers distributed to the pontomedullary reticular formation, the locus coeruleus, the raphe pontis, the pontine nuclei, and the dorsolateral tegmental nucleus and adjacent regions of the pontine gray. At mesodiencephalic levels, labeling was present in the rostral raphe nuclei (dorsal, median and linearis), the mesencephalic gray, the deep and intermediate layers of the superior colliculus, the medial and anterior pretectal nuclei, the ventral tegmental area, zona incerta as well as the mediodorsal and reticular nuclei of the thalamus. Injections of the parvocellular reticular nucleus labeled axons which coursed through the lateral medullary tegmentum to heavily innervate lateral regions of the medullary and caudal pontine reticular formation, cranial motor nuclei (hypoglossal, facial and trigeminal) and the parabrachial complex.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of lesions of the nucleus of the optic tract on optokinetic nystagmus and after-nystagmus in the monkey

Summary 1. The nucleus of the optic tract (NOT) and the dorsal terminal nucleus (DTN) of the accessory optic system were lesioned electrolytically or with kainic acid in rhesus monkeys. When lesions involved NOT and DTN, peak velocities of optokinetic nystagmus (OKN) with slow phases toward the side of the lesion were reduced, and optokinetic after-nystagmus (OKAN) was reduced or abolished. The jump in slow phase eye velocity at the onset of OKN was smaller in most animals, but was not lost. Initially, there was spontaneous nystagmus with contralateral slow phases. OKN and OKAN with contralateral slow phases were unaffected. 2. Damage to adjacent regions had no effect on OKN or OKAN with two exceptions: 1. A vascular lesion in the MRF, medial to NOT and adjacent to the central gray matter, caused a transient loss of the initial jump in OKN. The slow rise in slow phase velocity was prolonged, but the gain of OKAN was unaffected. There was no effect after a kainic acid lesion in this region in another animal. 2. Lesions of the fiber tract in the pulvinar that inputs to the brachium of the superior colliculus caused a transient reduction in the buildup and peak velocity of OKN and OKAN. 3. In terms of a previous model (Cohen et al. 1977; Waespe et al. 1983), the findings suggest that the indirect pathway that activates the velocity storage integrator in the vestibular system to produce the slow rise in ipsilateral OKN and OKAN, lies in NOT and DTN. Activity for the rapid rise in OKN, carried in the direct pathway, is probably transmitted to the pontine nuclei and flocculus via an anatomically separate fiber path-way that lies in the MRF. A fiber tract in the pulvinar that inputs to the brachium of the superior colliculus appears to carry activity related to retinal slip from the visual cortex to NOT and DTN.Abbreviations used in Figures BIC brachium of the inferior colliculus - BSC brachium of the superior colliculus - C caudate nucleus - CG central gray - CL Centralis lateralis - dbc decussation of the brachium conjunctivum - DTN dorsal terminal nucleus of the accessory optic system - IC inferior colliculus - Hb habenular nucleus - hc habenular commissure - LD lateralis dorsalis - LGn lateral geniculate nucleus - MD medialis dorsalis - MGn medial geniculate nucleus - MLF median longitudinal fasciculus - MRF mesencephalic reticular formation - cMRF central mesencephalic reticular formation - NL nucleus limitans - NLL nucleus of the lateral lemniscus - NOT nucleus of the optic tract - PB parabigeminal nucleus - pc posterior commissure - Pi pineal gland - PON pretectal olivary nucleus - Pt pretectum - Pulv pulvinar - R nucleus reticularis - RN red nucleus - RpN raphe nucleus - RTP nucleus reticularis tegmenti pontis - SC superior colliculus - SCpit superior cerebellar peduncle - VPL ventralis postero-lateralis - VPM ventralis posteromedialis - III oculomotor nucleus - IV trochlear nucleus - IVn trochlear nerve - Vm mesencephalic trigeminal nucleus     

Projections from the rostral parvocellular reticular formation to pontine and medullary nuclei in the rat: Involvement in autonomic regulation and orofacial motor control

The efferent connections of the rostral parvocellular reticular formation to pontine and medullary nuclei in the rat were studied with anterogradely transported Phaseolus vulgaris leucoagglutinin. Dense innervations from the rostral parvocellular reticular formation were found in the mesencephalic trigeminal nucleus, the supratrigeminal area, the motor trigeminal nucleus, the facial, hypoglossal and parabrachial nuclei and specific parts of the caudal parvocellular reticular formation, including nucleus linearis and the dorsal reticular nucleus of the medulla. The raphe nuclei, nucleus of the solitary tract, inferior olive, dorsal principal sensory, spinal trigeminal nuclei and gigantocellular reticular nucleus and the ventral reticular nucleus of the medulla received moderate projections. In general, the projections from the rostral parvocellular reticular formation were bilateral with an ipsilateral dominance. The dorsal motor vagus and the ambiguus nuclei were not labeled.

It is concluded that the rostral parvocellular reticular formation participates in regulation of orofacial motor control and in neural networks for limbic control of metabolic homeostasis.     

The effects of N-acetylaspartylglutamate and distribution of N-acetylaspartylglutamate-like immunoreactivity in the rat somatosensory thalamus

The ventrobasal thalamus and adjacent regions were stained for the presence of N-acetylaspartylglutamate-like immunoreactivity. Immunoreactive axonal terminals were observed in this area and also in certain non-specific thalamic nuclei, the reticular thalamic nucleus and the lateral geniculate nucleus. Stained somata were found in the habenula, centrolateral thalamic nucleus and reticular thalamic nucleus. Iontophoretically applied N-acetylaspartylglutamate had variable, although predominantly inhibitory, actions on ventrobasal thalamus neurons. These results indicate that N-acetylaspartylglutamate is unlikely to be the neurotransmitter of ascending somatosensory afferents, but do not rule out the possibility that it has some other neurotransmitter or neuromodulator role in the ventrobasal thalamus.     

Topographical organization of the brainstem afferents to the lateral posterior-pulvinar thalamic complex in the cat

Following stereotaxic injections of horseradish peroxidase in the dorsal thalamus of the cat which were restricted to the lateralis posterior-pulvinar complex, labelled neurons were found in the superficial layers of the superior colliculus and in the brainstem. The retrogradely-filled cells of the brainstem were situated principally in the nucleus tegmenti pedunculopontinus, the locus coeruleus complex, the parabrachial nuclei and the dorsal tegmental nucleus of Gudden; in each case, labelled cells were more numerous on the ipsilateral side. In addition, some scattered neurons were observed in the central grey matter, the mesencephalic reticular formation, the central superior and dorsal raphe nuclei, the cuneiform nucleus, the nucleus reticularis gigantocellularis, the nucleus praepositus hypoglossi and the oculomotor nuclei. A differential organization of these projections was observed.It is concluded that the rostrointermediate subdivision of the lateralis posterior-pulvinar complex receives most of its connections from the nucleus tegmenti pedunculopontinus, from the deep layers of the superior colliculus and from the other brainstem nuclei, while the caudal subdivision (extrageniculate visual subdivision) receives its main projection from the superficial layers of the superior colliculus. The findings may have functional implications for the role of the complex in oculomotor control.     

Projections to the rostral reticular thalamic nucleus in the rat

Summary Afferent pathways to the rostral reticular thalamic nucleus (Rt) in the rat were studied using anterograde and retrograde lectin tracing techniques, with sensitive immunocytochemical methods. The analysis was carried out to further investigate previously described subregions of the reticular thalamic nucleus, which are related to subdivisions of the dorsal thalamus, in the paraventricular and midline nuclei and three segments of the mediodorsal thalamic nucleus. Cortical inputs to the rostral reticular nucleus were found from lamina VI of cingulate, orbital and infralimbic cortex. These projected with a clear topography to lateral, intermediate and medial reticular nucleus respectively. Thalamic inputs were found from lateral and central segments of the mediodorsal nucleus to the lateral and intermediate rostral reticular nucleus respectively and heavy paraventricular thalamic inputs were found to the medial reticular nucleus. In the basal forebrain, afferents were found from the vertical and horizontal limbs of the diagonal band, substantia innominata, ventral pallidum and medial globus pallidus. Brainstem projections were identified from ventrolateral periaqueductal grey and adjacent sites in the mesencephalic reticular formation, laterodorsal tegmental nucleus, pedunculopontine nucleus, medial pretectum and ventral tegmental area. The results suggest a general similarity in the organisation of some brainstem Rt afferents in rat and cat, but also show previously unsuspected inputs. Furthermore, there appear to be at least two functional subdivisions of rostral Rt which is reflected by their connections with cortex and thalamus. The studies also extend recent findings that the ventral striatum, via inputs from the paraventricular thalamic nucleus, is included in the circuitry of the rostral Rt, providing further evidence that basal ganglia may function in concert with Rt. Evidence is also outlined with regard to the possibility that rostral Rt plays a significant role in visuomotor functions.Abbreviations ac anterior commissure - aca anterior commissure, anterior - Acb accumbens nucleus - AI agranular insular cortex - AM anteromedial thalamic nucleus - AV anteroventral thalamic nucleus - BST bed nucleus of stria terminalis - Cg cingulate cortex - CG central gray - CL centrolateral thalamic nucleus - CM central medial thalamic nucleus - CPu caudate putamen - DR dorsal raphe nucleus - DTg dorsal tegmental nucleus - EP entopeduncular nucleus - f fornix - Fr2 Frontal cortex, area 2 - G gelatinosus thalamic nucleus - GP globus pallidus - Hb habenula - HDB horizontal limb of diagonal band - IAM interanterodorsal thalamic nucleus - ic internal capsule - INC interstitial nucleus of Cajal - IF interfascicular nucleus - IL infralimbic cortex - IP interpeduncular nucleus - LC locus coeruleus - LDTg laterodorsal tegmental nucleus - LH lateral hypothalamus - LHb lateral habenular nucleus - ll lateral lemniscus - LO lateral orbital cortex - LPB lateral parabrachial nucleus - MD mediodorsal thalamic nucleus - MDL mediodorsal thalamic nucleus, lateral segment - Me5 mesencephalic trigeminal nucleus - MHb medial habenular nucleus - mlf medial longitudinal fasciculus - MnR median raphe nucleus - MO medial orbital cortex - mt mammillothalamic tract - OPT olivary pretectal nucleus - pc posterior commissure - PC paracentral thalamic nucleus - PF parafascicular thalamic nucleus - PPTg pedunculopontine tegmental nucleus - PrC precommissural nucleus - PT paratenial thalamic nucleus - PV paraventricular thalamic nucleus - PVA paraventricular thalamic nucleus, anterior - R red nucleus - Re reuniens thalamic nucleus - RRF retrorubral field - Rt reticular thalamic nucleus - Scp superior cerebellar peduncle - SI substantia innominata - sm stria medullaris - SNR substantia nigra, reticular - st stria terminalis - TT tenia tecta - VL ventrolateral thalamic nucleus - VO ventral orbital cortex - VP ventral pallidum - VPL ventral posterolateral thalamic nucleus - VTA ventral tegmental area - 3 oculomotor nucleus - 3V 3rd ventricle - 4 trochlear nucleus     

Evidence for a projection from the perireticular thalamic nucleus to the dorsal thalamus in the adult rat and ferret

Summary During early development, the perireticular thalamic nucleus is very large (i.e. has many cells) and has a strong projection to the dorsal thalamus and to the cerebral neocortex. By adulthood, the nucleus has much reduced in size and only a few cells remain. It is not clear whether these perireticular cells that remain into adulthood maintain their connections with the dorsal thalamus and with the neocortex. This study examines this issue by injecting neuronal tracers into various nuclei of the dorsal thalamus (dorsal lateral geniculate nucleus, medial geniculate complex, ventroposteromedial nucleus, lateral posterior nucleus, posterior thalamic nucleus) and into different areas of the neocortex (somatosensory, visual, auditory). After injections of tracer into the individual nuclei of the rat and ferret dorsal thalamus, retrogradely-labelled perireticular cells are seen. In general, after each injection, the retrogradely-labelled perireticular cells lie immediately adjacent to a group of retrogradely-labelled reticular cells. For instance, after injections into the medial geniculate complex, perireticular cells adjacent to the auditory reticular sector are retrogradely-labelled, whilst after an injection into the dorsal lateral geniculate nucleus, retrogradely-labelled perireticular cells adjacent to the visual reticular sector are seen. By contrast, injections of tracer into various areas of the rat and ferret neocortex result in no retrogradely-labelled cells in the perireticular nucleus. Thus, unlike during perinatal development when perireticular cells project to both neocortex and dorsal thalamus, perireticular cells in the adult seem to project to the dorsal thalamus only: the perireticular projection to the neocortex appears to be entirely transient.     

Somatosensory systems and the milk-ejection reflex in the rat. I. Lesions of the mesencephalic lateral tegmentum disrupt the reflex and damage mesencephalic somatosensory connections

Bilateral electrolytic lesions and unilateral tracer injections were performed in lactating rats in order to study the participation of the mesencephalic lateral tegmentum in the milk-ejection reflex. The release of oxytocin was detected as a rise in intramammary pressure during each milk ejection. In animals with lesions, the lateral part of the deep grey layers of the superior colliculus, the intercollicular area and the rostromedial portion of the external nucleus of the inferior colliculus were destroyed. The mesencephalic lateral tegmentum of animals in which the milk-ejection reflex was blocked sustained a larger damage than in rats where the frequency of the milk-ejection response was only slowed down. Solutions of True Blue, horseradish peroxidase or horseradish peroxidase coupled to wheat germ agglutinin were injected in the mesencephalic lateral tegmentum of rats with and without lesions. Retrogradely labelled cells were found in several nuclei of the somatosensory pathways: the principal sensory and spinal parts of the trigeminal complex, the cuneate and gracile nuclei, the lateral cervical nucleus and the nucleus proprius of the spinal cord. Labelled cells were also found in the ventral nucleus of the lateral lemniscus, the ventral parabrachial nucleus, the gigantocellular reticular nucleus, the lateral nucleus of the substantia nigra, the prerubral nucleus of the thalamus, the hypothalamic ventromedial nucleus, the zona incerta and in the anterior and lateral hypothalamic areas. Labelled fibres and "terminal-like" labelling were found in the anterior pretectal area, in the thalamic parafascicular nucleus, in the posterior nucleus and the ventroposterior complex, in the zona incerta and in the fields of Forel, but none were observed in the supraoptic or paraventricular nuclei. Injections made in the area of the lateral cervical nucleus and in the cuneate and gracile nuclei labelled fibres and "terminal-like" fields in the external nucleus of the inferior colliculus, the intercollicular area, the deep grey layers of the superior colliculus and in the mesencephalic lateral tegmentum. After injections in the posterior nucleus and ventroposterior complex of the thalamus, retrogradely labelled cells were found in the lateral tegmentum, the intercollicular area and the external nucleus of the inferior colliculus. These results indicate that bilateral lesioning of the mesencephalic lateral tegmentum, which disrupts the milk-ejection response, could damage somatosensory projections originating from the dorsal horn of the spinal cord, the lateral cervical nucleus, the dorsal column nuclei and the sensory and spinal trigeminal nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)     

Supramedullary projections to the dorsal and ventral divisions of the paramedian reticular nucleus in the cat

Summary Injections of combined lectin-conjugated and unconjugated horseradish peroxidase were made in the dorsal (d) and ventral (v) divisions of the paramedian reticular nucleus (PRN), a precerebellar relay nucleus, of the cat. The origins of supramedullary afferent projections to the PRN were identified in the pons, midbrain and cerebral cortex using the transverse plane of section. The data indicate a segregation of input from a number of sites to the dPRN and vPRN. The interstitial nucleus of Cajal projects bilaterally to the dPRN and predominantly to the ipsilateral side. The vPRN receives only a unilateral projection from the ipsilateral nucleus of Cajal. Major afferent projections to the vPRN arise from the ipsilateral nucleus of Darkschewitsch and the intermediate layer of the contralateral superior colliculus. Neither of these sites projected to the dPRN. The raphe nuclei and medial reticular formation of the pons and midbrain contribute a moderate input to both divisions of the PRN. A moderate bilateral cerebral cortical projection arises from the first somatomotor area (SMI). The ventral coronal and anterior sigmoid gyri project mainly to the dPRN and vPRN respectively. Smaller afferent projections arise from the posterior sigmoid gyri and area 6 of Hassler and Mühs-Clement (1964) in the medial wall of the anterior sigmoid gyrus. Inputs from the accessory oculomotor nuclei, tectal regions and the first somatomotor cortex suggest a role in postural control for the PRN which may underlie its involvement in mediating orthostatic reflexes.Abbreviations 3N oculomotor nerve - 5ME mesencephalic nucleus (trigeminal) - 5MN motor nucleus (trigeminal) - 5PN sensory nucleus, parvocellular division (trigeminal) - 5SM sensory nucleus, magnocellular division (trigeminal) - 12M hypoglossal nucleus - 12N hypoglossal nerve - AQ aqueduct - BC brachium conjunctivum - BP brachium pontis - CAE nucleus caeruleus - Cl inferior central nucleus (raphe) - CM centromedian nucleus - CNF cuneiform nucleus - CS superior central nucleus (raphe) - D nucleus of Darkschewitsch - DRM dorsal nucleus of the raphe (median division) - EW Edinger-Westphal nucleus - FTC central tegmental field - FTG gigantocellular tegmental field - FTP paralemniscal tegmental field - ICA interstitial nucleus of Cajal - ICC inferior colliculus (central nucleus) - INC nucleus incertus - INT nucleus intercalatus - ION inferior olivary nucleus - LLV ventral nucleus of lateral lemniscus - LP lateral posterior complex of thalamus - MGN medial geniculate nucleus - MLF medial longitudinal fasciculus - TN nucleus of optic tract - P pyramidal tract - PCN nucleus of posterior commissure - PF parafascicular nucleus - PH nucleus praepositus hypogloss - PRN paramedian reticular nucleus (a — accessory division; d — dorsal division; v — ventral division) - PUL pulvinar - SCD superior colliculus (deep layer) - SNC substantia nigra (compact division) - SON superior olivary nucleus - RM red nucleus (magnocellular) - RR retrorubral nucleus - TB trapezoid body - TDP dorsal tegmental nucleus (pericentral division) - TRC tegmental reticular nucleus (central division) - TV ventral tegmental nucleus - V3 third ventricle - V4 fourth ventricle - VB ventrobasal complex of thalamus - VIN inferior vestibular nucleus - VSN superior vestibular nucleus - ZI zona incerta Supported by the Medical Research Council of Canada     

Is ethylcholine mustard aziridinium ion a specific cholinergic neurotoxin?

The histopathologic effects of different doses of ethylcholine mustard aziridinium ion infused into the caudate-putamen complex or nucleus basalis were evaluated in rats. Although no non-specific tissue damage was observed at the lowest doses of ethylcholine mustard aziridinium ion examined--0.01 nmol in 1-microliter vehicle and 0.02 nmol in 2-, 5-, and 10-microliters vehicle in both the striatum and nucleus basalis--minimal but definite non-selective pathology, characterized by gliosis and loss of all neuronal elements in the region affected by the nitrogen mustard, was observed in both targets at a dose of 0.02 nmol 1 microliter and more severely at all doses containing 0.05 and 0.1 nmol ethylcholine mustard aziridinium ion. At doses of ethylcholine mustard aziridinium ion containing 0.2 nmol of the cytotoxin and greater amounts, non-specific cell loss in intact tissue and extensive cavitation became increasingly the most prominent histologic features of drug action. No statistically significant effects of ethylcholine mustard aziridinium ion on striatal choline acetyltransferase activities were found until doses of 0.4 nmol/1 microliter or greater were injected, concentrations of the cytotoxin at which appreciable non-specific pathology was also observed. Levels of dopamine in the caudate-putamen nucleus were reduced by comparatively greater amounts than choline acetyltransferase at doses of 2.5 nmol/2 microliters, 5.0 nmol/2 microliters and 10 nmol/2 microliters cytotoxin, but a significant effect of ethylcholine mustard aziridinium ion on striatal L-glutamate decarboxylase activity was found only at a dose of 10 nmol/2 microliters. As no dose of ethylcholine mustard aziridinium ion was found that reduced choline acetyltransferase without producing considerable non-specific tissue destruction, the usefulness of the cytotoxin in studying the behavioral and physiological consequences of selective cholinergic hypofunction in the brain must be questioned.     

长翼蝠(Miniopterus Schrebersi)上丘与传递超声信息有关核团的传入联系—HRP法

用HRP逆行追踪法结合电生理学技术,对21只长翼蝠上丘(SC)超声信息的传入联系进行了形态学研究。13只动物上丘的听应部位电泳HRP后,标记神经元恒定地出现于双侧的下丘(IC,同侧为主)和外侧丘系背核(DNLL,对侧占优势)。约半数动物的同侧前外侧橄榄周核(ALPO)存在标记神经元。此外,标记神经元还出现于下列结构中,同侧的舌下神经前置核(n.Ⅻ)、小脑顶核(F)、黑质(SN)、后连合核(NPC)、丘脑(THa)、未定带(ZI),对侧的小脑齿状核(D)、双侧的中脑网状结构(MRF)、上丘(SC)。8只长翼蝠上丘的非听反应部位电泳HRP后,同侧的舌下神经前置核、小脑顶核、黑质、后连合核、丘脑、未定带,对侧的小脑齿状核,双侧的中脑网状结构及上丘亦见标记神经元。本实验提示:上丘的超声信息主要是经过同侧前外側橄榄周核和下丘以及对侧的外侧丘系背核中继传入的。     

Afferent connections of the mesencephalic reticular formation: A horseradish peroxidase study in the rat

The afferent connections of the mesencephalic reticular formation were studied experimentally in the rat by the aid of the retrograde horseradish peroxidase tracer technique. The results suggest that the rostral portion of the mesencephalic reticular formation receives its main input from the cerebral cortex, the zona incerta and the fields of Forel, the central gray substance, the nuclei reticularis pontis oralis and caudalis, and the deep cerebellar nuclei. Substantial input to the same territory of the mesencephalic reticular formation appears to come from the superior colliculus, the substantia nigra, the parabrachial area, the spinal trigeminal nucleus, and the nucleus reticularis gigantocellularis, whereas several other brain structures, among which the locus coeruleus and the raphe complex, seem to represent modest but consistent additional input sources. The afferentation of more caudal portions of the mesencephalic reticular formation appears to conform to the general pattern outlined above with only three exceptions: the cerebral cortex, the deep cerebellar nuclei and the spinal trigeminal nucleus seem to be relatively modest sources of projections to these levels.Considering that the mesencephalic reticular formation is a critical structure in the “ascending activating systems”, the present results, confirming and extending those of many other investigators, characterize a set of pathways that seem to be an important part of the anatomical substrate of the sleep-waking cycle.