Spinal projections from the periaqueductal grey and dorsal raphe in the rat,cat and monkey

There is considerable evidence that the periaqueductal grey and the dorsal raphe contribute to an endogenous analgesia system and to the regulation of a wide variety of other responses, many of which involve spinal sites of action. To map the areas of the periaqueductal grey and dorsal raphe which contain neurons that project to the spinal cord, wheat germ agglutinin conjugated to horseradish peroxidase was injected into hemisected spinal cords in rat, cat, and monkey. After cervical or lumbar injections labelled neurons were found in the periaqueductal grey and dorsal raphe in all species examined. In the rat, labelling of the dorsal raphe is sparse but numerous labelled neurons are present in the mid and rostral periaqueductal grey. In the cat, the number of retrogradely-labelled neurons in both the dorsal raphe and the periaqueductal grey are considerable. In the monkey, like the rat, the labelling in the dorsal raphe was light but numerous labelled neurons were present in the periaqueductal grey and the adjacent nucleus cuneiformis. Injections into the lumbar spinal cord produced the same pattern of labelling as seen after cervical level injections with approximately 40% fewer labelled cells in all areas. Thus, while each species had a similar pattern of spinal projections from the periaqueductal grey and dorsal raphe, quantitative differences were evident among the species examined.These results suggest that the number of periaqueductal grey and dorsal raphe neurons projecting to the spinal cord in the rat, cat and monkey are considerably more numerous than previously reported and that the effects described during the stimulation of these regions could be, at least partly, due to the involvement of these direct pathways.     

The distribution pattern of the sympathetic nerve fibers to the cerebral arterial system in rat as revealed by anterograde labeling with WGA-HRP

Summary To clarify the projection route and the expansion of the terminal plexus of the sympathetic nerve fibers innervating the cerebral arterial system in rat, we labeled the postganglionic fibers originating in the superior cervical ganglion and traced their entire course by anterograde labeling with wheat germ agglutinin-horseradish peroxidase. Sympathetic innervation of the internal cerebral artery by labeled fibers actually began just at the portion where it enters the intradural space, and innervated it up to the small pial arteries located in the subarachnoid space, but not the intracerebral arterioles. On the main arteries in the circle of Willis, bundles of nerve fibers ran parallel to the long axis of the vessels and branched perpendicularly their terminal twigs with regular intervals to form a rib-structure pattern. On the arterial branches derived from the circle of Willis, a fine nerve bundle and delicate terminal axons formed a meshwork instead of a rib-structure pattern. These observations confirmed the existence of differences in the distribution pattern of the nerve plexus, which strongly affects the strength and quality of vasoconstriction by sympathetic activation in each level of the cerebral arterial system.     

大鼠延髓和脊髓背角的PKCγ阳性神经元向丘脑胶状核投射

目的 :观察大鼠延髓和脊髓背角内蛋白激酶Cγ亚单位 (PKCγ)阳性神经元向丘脑胶状核的投射。方法 :荧光金 (FG)逆行追踪与PKCγ免疫荧光组织化学染色相结合的双标记技术。结果 :PKCγ阳性神经元主要分布于大鼠延髓和脊髓背角的II层内侧部及II、III层交界处 :将FG注入丘脑胶状核后 ,在延髓背角的I、III层和脊髓背角的I、III、V层及外侧脊核内可见FG标记神经元 ;延髓和脊髓背角I层的部分FG标记神经元呈PKCγ阳性。结论 :大鼠延髓和脊髓背角的PKCγ阳性神经元向丘脑胶状核投射 ,它们可能参与将伤害性刺激信息向丘脑的传递。     

Projections from the diencephalon and mesencephalon to nucleus paragigantocellularis lateralis in the cat

The distribution of labelled cells in the diencephalon and mesencephalon has been mapped following injections of horseradish peroxidase into nucleus paragigantocellularis lateralis in the cat. Most of the labelled cells were found ipsilateral to the injection site. A group of small and medium-sized labelled perikarya (11-40 microns in diameter) was present in the caudal part of the periaqueductal grey matter (A3-P2) and in the adjacent tegmentum. Small, round or fusiform cells (8-25 microns were labelled in the tuberal region of the hypothalamus in the dorsomedial hypothalamus and in the lateral hypothalamic area. It is suggested that the cardiovascular responses which can be elicited by stimulation in these regions of the periaqueductal grey and hypothalamus are mediated via a relay on to spinally projecting neurones in nucleus paragigantocellularis lateralis which synapse on sympathetic preganglionic neurones in the intermediolateral cell column.     

An ipsilateral projection from the red nucleus to the lateral reticular nucleus in the cat

Summary Injections of the wheat germ agglutinin — horse-radish peroxidase complex into the lateral reticular nucleus reveal that in addition to the well known contralateral rubroreticular connection, there is also a small but clear cut ipsilateral projection. Cells of various sizes participate in this ipsilateral pathway, and the retrogradely labelled neurons lie dispersed throughout the entire red nucleus.     

The cerebellar projection from the paratrigeminal nucleus in the cat

The cerebellar afferent projection from the paratrigeminal nucleus (PTN) was studied in the cat by means of retrograde axonal transport of horseradish perioxidase (HRP). Most of the afferent fibres reach the cerebellar lobules I, II, V (hemispheral part), VIIIB and IX, the paramedian lobule and the fastigial nucleus. The total distribution of the cerebellar afferents is shown in Fig. 2. The findings extend Chan-Palay's [2,3] recent studies on the cytology, synaptic organization and neurotransmitter content of the paratrigeminal nucleus in monkey and rat.     

Projections from the ventral tegmental area and mesencephalic raphe to the dorsal raphe nucleus in the rat

Summary The origins of the dopaminergic innervation of the rat dorsal raphe nucleus (NRD) have been investigated using a combination of fluorescent retrograde tracing and fluorescence histochemistry. Stereotaxic microinjections of True Blue were placed in the central, caudal and lateral portions of the NRD, and after 6–12 days survival the brains were processed for fluorescence histochemical detection of catecholamines. Retrogradely labeled neurons were searched for in the diencephalic A11 and A13 dopaminergic cell groups, substantia nigra, ventral tegmental area (VTA) and the linear, central superior and dorsal raphe nuclei. The various NRD injections consistently resulted in retrograde labeling of a small number of catecholamine-containing, presumed dopaminergic cell bodies, confined mainly to three regions: the VTA, the linear and central superior raphe nuclei and the NRD itself. The present findings indicate that not only dopaminergic neurons in the VTA but also the system of catecholamine-containing cells, extending dorsally and caudally from the VTA within the midline raphe area, project to the NRD. Although often similar in size, shape and distribution to the catecholaminergic neurons the majority of retrogradely labeled cells in these regions were, however, found to be non-catecholaminergic.Abbreviations 3 Principal oculomotor nucleus - 4 Trochlear nucleus - Aq Cerebral aqueduct - cp cerebral peduncle - cst cortico-spinal tract - dscp decussation of the superior cerebellar peduncle - DTg Dorsal tegmental nucleus - fr fasciculus retroflexus - IF Interfascicular nucleus - IP Interpeduncular nucleus - LL nucleus of the lateral lemniscus - ml medial lemniscus - mlf medial longitudinal fasciculus - mNV mesencephalic trigeminal nucleus - NLC Nucleus linearis caudalis - NLR Nucleus linearis rostralis - NRD Dorsal raphe nucleus - PAG Periaqueductal grey - PN Pontine nucleus - PRN Pontine raphe nucleus - R Red nucleus - RCS Nucleus raphe centralis superior - SN Substantia nigra - VTA Ventral tegmental area - VTg Ventral tegmental nucleus     

Projections of reticular neurones to dorsal regions of the spinal cord in the cat

Reticulospinal neurones in the cat were identified by extracellular recording and antidromic stimulation of their axons in the cord. Approximately 34% of reticulospinal neurones in the medulla, and 28% in the pons, were found to project to dorsal regions of the cord, between T9 and L2. Most of these neurones had one branch situated dorsally and another in the ventral or ventrolateral funiculus. Some branches travelled for short distances in the dorsal columns. Microstimulation techniques demonstrated the presence of branches of reticulospinal fibres in the dorsal horn. The results may provide an anatomical basis for the widespread effects of stimulation of the reticular formation on afferent transmission in the spinal cord.     

A projection from the periaqueductal grey to the lateral reticular nucleus in the cat

Summary A projection from the periaqueductal grey (PAG) to the lateral reticular nucleus (NRL) in the cat was demonstrated by means of retrograde transport of the wheat germ agglutinin-horseradish peroxidase complex. The connection has its main origin ipsilaterally in the ventral part of the caudal PAG, but scanty projections from other parts of the PAG were also found. The neurons projecting to the NRL are of varying shapes and sizes, but most cells have a maximum diameter of less than 20 m. The findings are discussed in relation to the other afferent and efferent connections of the NRL.     

A ventral lateral geniculate nucleus projection to the dorsal thalamus and the midbrain in the cat

Summary Retrograde tracing experiments using horseradish peroxidase (HRP) have been utilized for demonstrating the origin of efferent projections of the ventral lateral geniculate nucleus (LGNv) in the cat. HRP-positive cells identifiable as origins of thalamic projections were found in LGNv after injections of HRP into the lateral central intralaminar nucleus. The labeled cells appeared concentrated in the medial part of the internal division of LGNv, consisting of medium-sized multipolar cells. Contralaterally, fewer labeled cells were present in the corresponding part of LGNv. In the case of injections of HRP into the midbrain (pretectum and superior colliculus), labeled cells in LGNv were distributed almost exclusively in its external division, composed of mainly small cells. Little overlap of the distribution of HRP-positive cells was seen in LGNv between the thalamic and midbrain injection cases.Abbreviations Ad Dorsal anterior nucleus - Am Medial anterior nucleus - Av Ventral anterior nucleus - BSC Brachium of superior colliculus - Cg Central gray - Cl Lateral central nucleus - Ld Dorsal lateral nucleus - LGNd Dorsal lateral geniculate nucleus - LGNv Ventral lateral geniculate nucleus - Lp Posterior lateral nucleus - Md Dorsal medial nucleus - NIII Oculomotor complex - NOT Nucleus of the optio tract - NPC Nucleus of posterior commissure - OT Optic tract - P Posterior nucleus (Rioch 1929) - Pc Paracentral nucleus - Po Posterior group of thalamic nuclei - Pt Parataenial nucleus - PTa Anterior pretectal nucleus - PTm Medial pretectal nucleus - PTp Posterior pretectal nucleus - Pul Pulvinar - R Red nucleus - Rt Thalamic reticular nucleus - Sg Suprageniculate nucleus - Va Anterior ventral nucleus - VI Lateral ventral nucleus - Vm Medial ventral nucleus - Vpl Posterolateral ventral nucleus - Vpm Posteromedial ventral nucleus - Zi Zona incerta - II Layer of superior colliculus - III Layer of superior colliculus - IV (Kanaseki and Sprague, 1974)     

Projections of the dorsal raphe nucleus and midbrain central gray substance to the cat limbic system

Morphological organization of connections of ventro-lateral (nociceptive) and dorso-lateral (analgetic) midbrain central gray (vl SGC and dl SGC), as well as of dorsal raphe nucleus (analgetic zone, Rd), with different limbic structures, responsible for the formation of various emotional states, was studied in 26 cats. The methods of electrical destruction of brain areas were used that were followed by the light and electron microscopic study of degenerating fibers and synapses. Heterogeneity of connections of above mentioned formations with different limbic structures was demonstrated. Connections Rd and dl SGC with upstream limbic structures were found to be very similar in their organization and expression. Connections of vl SGC with the same structures were significantly different. It is suggested that similar (antinociceptive) function of dl SGC and Rd has determined the likeness of their connections. This, in combination with the heterogeneity of SGC in conduction of the pain and analgesia, supports the identification of two brain systems: nociceptive, conducting pain sensitivity, and antinociceptive, inhibiting its conduction. The nociceptive system includes the following structures: vl SGC, posterior and lateral hypothalamic nuclei, preoptic area. In the antinociceptive system two subsystems could be distinguished: midbrain units of these subsystems are localized in different structures (Rd and dl SGC), while the upstream ones are found in the same hypothalamic nuclei--ventromedial, dorsomedial, paraventricular. As far as septum, amigdala, hippocampus and cingular cortex are concerned, it was found impossible to refer them to any of these systems--either nociceptive or antinociceptive--basing solely on the findings of morphological studies because of approximately similar representation of axons of neurons in vl SGC, dl SGC, Rd in these structures.     

Afferent connections of the zona incerta: a horseradish peroxidase study in the rat

Restricted microelectrophoretic injections either of free horseradish peroxidase or of horseradish peroxidase conjugated with wheat germ agglutinin were given to albino rats in order to study the afferent connections of structures of the subthalamic region. The results suggest that the zona incerta receives its main input from several territories of the cerebral cortex, the mesencephalic reticular formation, deep cerebellar nuclei, regions of the sensory trigeminal nuclear complex and the dorsal column nuclei. Substantial input to the zona incerta appears to come from the superior colliculus, the anterior pretectal nucleus and the periaqueductal gray substance, whereas many other structures, among which hypothalamic nuclei, the locus coeruleus, the raphe complex, the parabrachial area and medial districts of the pontomedullary reticular formation, seem to represent relatively modest but consistent additional input sources. The afferentation of neurons in Forel's fields H1 and H2 appears to conform to the general pattern outlined above. As pointed out in the Discussion, the present results provide hodological support for the classic concept according to which the zona incerta can be regarded as a rostral extent of the midbrain reticular core. Some of the possible physiological correlates of the fiber connections of the zona incerta in the context of the sleep-waking cycle, ingestive behaviors, somatic motor mechanisms, visual functions and nociceptive behavior are briefly discussed.     

Projections from the globus pallidus to the thalamic areas projecting to the dorsal area 6 of the macaque monkey: a multiple tracing study

In the brains of 3 Japanese monkeys (Macaca fuscata), a combined injection of the tract-tracers Fast Blue (FB), Diamidino Yellow (DY), and horseradish peroxidase-conjugated with wheat germ agglutinin (WGA-HRP) was performed: the retrograde tracers, FB and DY, were injected into a rostral and a caudal sectors of the dorsal part in area 6, and the anterograde tracer, WGA-HRP, was injected into the internal segment of the globus pallidus (GPi). In the thalamus, FB- and DY-labeled neurons were distributed in a segregated manner. A substantial number of the FB-labeled and DY-labeled thalamic neurons were located within the thalamic areas containing fine axons labeled with WGA-HRP. The results suggest that the GPi may project to both the rostral and caudal sectors of the dorsal part of area 6 through the thalamus.     

Projections from the raphe nuclei to the phrenic motor nucleus in the cat

The monoclonal antibody HNK-1 binds to a carbohydrate determinant in the myelin-associated glycoprotein (MAG) and other glycoproteins of human peripheral nerve. Some glycoproteins of lower Mr than the major P0 glycoprotein of myelin appear to bind more antibody than MAG. These glycoproteins electrophorese in the Mr range of 20,000 to 26,000 and are present in the purified myelin fraction. The results indicate that an antigen on the surface of a subset of lymphocytes is shared with a group of glycoproteins in human peripheral nerve. The antigen appears to be similar to that recognized by IgM paraproteins associated with a type of neuropathy.     

The laminar distribution of cortical connections with the tecto- and cortico-recipient zones in the cat's lateral posterior nucleus

The anterograde and retrograde transport of wheat germ agglutinin congugated to horseradish peroxidase was used to examine the laminar organization of cortical connections with the two visual zones that comprise the cat's lateral posterior nucleus. Microelectrophoretic deposits of the tracer into the principal tecto-recipient zone in the medial division of the lateral posterior nucleus revealed reciprocal connections with the following cortical fields: areas 19 and 21a, the medial and lateral banks of the middle suprasylvian sulcus, and the dorsal and ventral banks of the lateral suprasylvian sulcus, which correspond to the dorsal lateral suprasylvian and ventral lateral suprasylvian visual areas of Palmer et al. [(1978) Brain Res. 177, 237-256] and an area in the fundus of the posterior suprasylvian sulcus. In each of these cortical areas two distinct populations of cells were labeled, small pyramidal neurons in layer VI and large pyramidal cells in layer V. Overlying these backfilled cells were two bands of anterograde label, a narrow strip in layer I and a wide band centered in layer IV. Deposits of wheat germ agglutinin conjugated to horseradish peroxidase confined to the striate-recipient zone in the lateral portion of the lateral posterior nucleus resulted in cortical label in areas 17, 18, 19, 20a and b, 21a, the medial and lateral banks of the middle suprasylvian sulcus, the posterior suprasylvian sulcus and in the fundus of the splenial sulcus. In all cortical areas other than 17 and 18, the laminar distribution of label was the same as that found after deposits of the tracer into the medial division of the lateral posterior nucleus. In contrast, areas 17 and 18 contained backfilled cells that were confined to layer V and anterograde label that was restricted to layer I. These findings indicate that the cortical areas that receive a direct projection from the A laminae of the dorsal lateral geniculate nucleus maintain a distinct laminar organization of reciprocal connections with the extrageniculate visual thalamus. Conversely, all other visual areas of the cortex share a common pattern of reciprocal connections with both the tecto- and striate-recipient zones of the lateral posterior nucleus.     

Cerebellar cortical and nuclear afferents from the Edinger-Westphal nucleus in the cat

Summary The cerebellar projection from the Edinger-Westphal nucleus was studied in the cat by means of retrograde transport of the wheat germ agglutinin-horseradish peroxidase complex. The present findings give evidence that the flocculus is the main terminal area. However, small tracer implants and injections into various parts of the cerebellar nuclei and cortex revealed projections also to the fastigial and interposed nuclei and to most parts of the anterior and posterior lobe cortices. The projecting neurons are small and located bilaterally throughout the Edinger-Westphal nucleus. No topical differences between the projections to different parts of the cerebellum were found.     

The medullary projection from the mesencephalic trigeminal nucleus. An experimental study with comments on the intrinsic trigeminal connections

Summary The medullary projection from the mesencephalic trigeminal nucleus has been studied in cats where the wheat germ agglutinin-horseradish peroxidase complex has been used as a retrograde and anterograde tracer. All injections were made at the level of the caudal pole of the inferior olive and show that it is especially the lateral part of nucleus parvicellularis of the reticular formation which is the main area for termination of the fibres. In addition, it can not be excluded that the descending fibres also reach the medialmost part of the spinal trigeminal sensory nucleus (pars magnocellularis and the adjoining pars gelatinosa). All three cell types of the mesencephalic trigeminal nucleus are labelled, the large globular, the small globular and the polygonal cells. Some of these cells are only faintly labelled. The observations confirm previous studies of the intrinsic trigeminal connections, but show that when the wheat germ agglutinin-horseradish peroxidase complex is used as a tracer, the origin as well as the termination for the intrinsic fibres (also the commissural) can be studied in the same section. The use of this sensitive tracer also shows new details within the intrinsic connections. The findings are discussed with special reference to the recent observations by Ruggiero et al. (1982). These authors found that in rabbit and rat there is a more restricted termination for the descending mesencephalic trigeminal fibres. The discrepancies between the observations seem to indicate that there are species differences as regards the connections between the mesencephalic trigeminal nucleus and the nuclei in the lower part of the brain stem.     

Projections from the paralemniscal nucleus to the spinal cord in the mouse

The present study investigated the projection from the paralemniscal nucleus (PL) to the spinal cord in the mouse by injecting the retrograde tracer fluoro-gold to different levels of the spinal cord and injecting the anterograde tracer biotinylated dextran amine into PL. We found that PL projects to the entire spinal cord with obvious contralateral predominance—420 neurons projected to the contralateral cervical cord and 270 to the contralateral lumbar cord. Fibers from PL descended in the dorsolateral funiculus on the contralateral side and terminated in laminae 5, 6, 7, and to a lesser extent in the dorsal and ventral horns. A smaller number of fibers also descended in the ventral funiculus on the ipsilateral side and terminated in laminae 7, 8 and, to a lesser extent in lamina 9. The present study is the first demonstration of the PL fiber termination in the spinal cord in mammals. The PL projection to the spinal cord may be involved in vocalization and locomotion.     

Projections to the hypothalamus from buffer nerves and nucleus tractus solitarius in the cat

In 18 cats anesthetized with chloralose, electrical activity of spontaneously active hypothalamic units was monitored for changes in firing frequency during electrical stimulation of carotid sinus (CSN) and aortic depressor (ADN) nerves and the nucleus tractus solitarius (NTS). Stimulation of the CSN altered the activity of 55% (381/691) of the tested. These responsive units were widely distributed in the ipsi- and contralateral hypothalamus. Of the units tested during stimulation of the ADN only 6% (17/274) changed their firing frequency. Responsive units were located only on the ipsilateral side and primarily in the paraventricular and supraoptic nuclei, Electrical stimulation of the NTS altered the firing frequency of all 84 hypothalamic units previously identified by stimulation of the CSN. NTS stimulation elicited responses that had a significantly shorter latency and followed significantly higher frequencies of stimulation when compared to stimulation of the CSN. These results demonstrate that the two buffer nerves have distinctly different central projections to the hypothalamus and suggest different functional roles for the ADN and CSN in homeostatic regulatory mechanisms mediated by the hypothalamus.