The reticulocerebellar projection in the cat as studied with retrograde transport of horseradish peroxidase

Summary Injections of horseradish peroxidase into the various parts of the cerebellar cortex and the cerebellar nuclei in the cat result in labelled cells within the reticular formation proper. All the reticular nuclei (with the exception of the reticular formation of the mesencephalon) send fibres to the cerebellum. The highest number of labelled neurons after cerebellar injections is found in the caudal reticular formation, especially within nucleus reticularis ventralis, nucleus reticularis lateralis and nucleus reticularis gigantocellularis. Another region for an accumulation of labelled cells is the rostral part of nucleus reticularis pontis caudalis.Except for the paraflocculus, all cerebellar cortical areas and all cerebellar nuclei receive afferents from one or more of the nuclei within the reticular formation proper, but the largest number of labelled neurons is observed in cases with injections including the intermediate-lateral part of lobulus simplex and the adjacent areas of the anterior lobe and crus I. The projection is bilateral with an ipsilateral preponderance (the cerebellar nuclei appear to receive a higher number of fibres from the contralateral side). Cells of all sizes are labelled, but labelled giant cells are found only after large cortical injections.     

Glutaminase-like immunoreactivity in the lower brainstem and cerebellum of the adult rat

Distribution of putative glutamatergic neurons in the lower brainstem and cerebellum of the rat was examined immunocytochemically by using a monoclonal antibody against phosphate-activated glutaminase, which has been proposed to be a major synthetic enzyme of transmitter glutamate and so may serve as a marker for glutamatergic neurons in the central nervous system. Intensely-immunolabeled neuronal cell bodies were densely distributed in the main precerebellar nuclei sending mossy fibers to the cerebellum; in the pontine nuclei, pontine tegmental reticular nucleus of Bechterew, external cuneate nucleus, and lateral reticular nucleus of the medulla oblongata. Phosphate-activated glutaminase-immunoreactive granular deposits were densely seen in the brachium pontis and restiform body, suggesting the immunolabeling of mossy fibers of passage. In the cerebellum, neuropil within the granule cell layer of the cerebellar cortex displayed intense phosphate-activated glutaminase-immunoreactivity, and that within the deep cerebellar nuclei showed moderate immunoreactivity. These results indicate that many mossy fiber terminals originate from phosphate-activated glutaminase-containing neurons and utilize phosphate-activated glutaminase for the synthesis of transmitter glutamate. Intensely-immunostained neuronal cell bodies were further observed in other regions which have been reported to contain neurons sending mossy fibers to the cerebellum; in the dorsal part of the principal sensory trigeminal nucleus, dorsomedial part of the oral subnucleus of the spinal trigeminal nucleus, interpolar subnucleus of the spinal trigeminal nucleus, paratrigeminal nucleus, supragenual nucleus, regions dorsal to the abducens nucleus and genu of the facial nerve, superior and medial vestibular nuclei, cell groups f, x and y, hypoglossal prepositus nucleus, intercalated nucleus, nucleus of Roller, reticular regions intercalated between the motor trigeminal and principal sensory trigeminal nuclei, linear nucleus, and gigantocellular and paramedian reticular formation. Neuronal cell bodies with intense phosphate-activated glutaminase-immunoreactivity were also found in other brainstem regions, such as the paracochlear glial substance, posterior ventral cochlear nucleus, and cell group e. Although it is still controversial whether all glutamatergic neurons use phosphate-activated glutaminase in a transmitter-related process and whether phosphate-activated glutaminase is involved in other metabolism-related processes, the neurons showing intense phosphate-activated glutaminase-immunoreactivity in the present study were suggested to be putative glutamatergic neurons.     

Organization of afferent connections to the lateral and interpositus cerebellar nuclei from the brainstem relay nuclei: a horseradish peroxidase study in the cat

Afferent projections to the lateral (dentate) and interpositus cerebellar nuclei from the brainstem relay nuclei were studied in cats using the horseradish peroxidase (HRP) method. In the first series of experiments, HRP was injected into the brachium pontis. Mossy fiber terminals were anterogradely labeled, predominantly in the lateral (hemispherical) part, moderately in the intermediate part, and slightly in the vermal part of the cerebellum. Besides these terminals in the cerebellar cortex, axon terminals labeled anterogradely were also found in the cerebellar nuclei. The labeled terminals appeared almost exclusively in the lateral nucleus and rarely in the interpositus nucleus. Cells labeled retrogradely were found both in the pontine nuclei and the tegmental reticular nucleus, but not in other brainstem nuclei. In the second series of experiments, HRP was injected into the lateral and interpositus nuclei, and retrograde labeling was examined in the brainstem relay nuclei. After HRP injection into the lateral nucleus, the number of labeled cells was significantly large in the pontine nuclei, but fairly small in the reticular or vestibular nuclei. The number of labeled cells was generally large in the inferior olive, mainly in the principal olive. After HRP injection into the interpositus nucleus, the number of labeled cells was moderate in the reticular or vestibular nuclei, but small in the pontine nuclei. The number of labeled cells in the inferior olive was also large, being distributed mainly in the accessory olives. These results indicate that the pontine nuclei and the principal olive provide major afferent inputs to the lateral nucleus, whereas the reticular nuclei, the vestibular nuclei and the accessory olives are the major afferent sources to the interpositus nucleus.     

Development of calretinin-immunoreactive unipolar brush-like cells and an afferent pathway to the embryonic and early postnatal mouse cerebellum

In the developing mouse hindbrain, immunoreactivity for calretinin, a calcium-binding protein, was first observed at embryonic day 10, and was localized to neuronal cell bodies in the reticular formation. By embryonic day 12, fibers emanated rostrally from the calretinin-immunoreactive neurons, extended dorsally and then caudally in the uncinate fasciculus to reach the developing cerebellar plate. These fibers crossed the cerebellar midline and were distributed to the contralateral side of the cerebellum. The number and intensity of staining of cell bodies in the reticular formation was reduced in postnatal mice. After postnatal day 1, it was no longer possible to discern the calretinin-immunoreactive fiber bundle in the brainstem, although fibers were still visible at the level of the uncinate fasciculus and in the cerebellum. We also observed intensely calretinin-immunoreactive, smaller cells in the cerebellum (embryonic day 14) and dorsal cochlear nuclei (embryonic day 18), most of which we believe are destined to become the unipolar brush, (also known as pale or monodendritic) cells observed in the adult mammalian brain. An immature form of these cells exists in the developing mouse cerebellum. Thus, using calretinin antiserum as a marker, an afferent neuronal system was described which projects to the cerebellar primordium. It is suggested that the calretinin-containing hook bundle is an afferent projection which provides a feed-forward neuronal system to the cerebellum which, in turn, projects afferent fibers to the calretinin-containing and other cells of the reticular formation.     

Cerebellar connections to the rostral reticular nucleus of the thalamus in the rat

We studied the cerebellar connections to the reticular nucleus thalamus (RNT) by means of retrograde axonal transport of horseradish peroxidase (HRP) in the rat. Specific HRP pressure injections to the rostral RNT (1.6-1.8 mm caudal to bregma) resulted in retrograde labelling of neurones in the cerebellar nuclei. The rostral RNT showed specific topographical organization of its cerebellar connections. Microinjections into the rostral RNT, 1.6 mm caudal to bregma, produced numerous HRP-labelled neurones within the anterior interposed (emboliform nucleus) and scarce HRP-labelled neurones within the lateral (dentate nucleus) cerebellar nuclei, whereas injections into the rostral RNT, 1.8 mm caudal to bregma, produced numerous HRP-labelled neurones within the posterior interposed (globose nucleus) and scarce lightly HRP-labelled neurones within the lateral (dentate nucleus) cerebellar nuclei. Cerebellar connections with the rostral RNT were exclusively ipsilateral to the injection site. No HRP-labelled cells were detected in the medial (fastigial nucleus) cerebellar nucleus. The cerebellar connections reach the RNT via the superior cerebellar peduncle. By contrast, HRP injections into the anterior, posterior interposed and lateral cerebellar nuclei produced no labelled cells within the RNT. This study demonstrates the existence of direct cerebello-RNT but not RNT-cerebellar connections. The presence of the cerebello-RNT connections introduces a new route through which the cerebellum may influence RNT and thus cerebral cortical activity.     

Nesfatin-1 immunoreactivity in rat brain and spinal cord autonomic nuclei

Nesfatin-1 is one of the peptide products of posttranslational processing of the nucleobindin-2 (NUCB2) gene, suggested to have physiological relevance to suppress food intake and body weight gain in rats. Nesfatin-1-immunoreactive cells have been found in distinct nuclei in the rat brain related to circuitries regulating food intake. Here, we report novel yet undescribed localization of NUCB2/nesfatin-1 at the mRNA and protein level in the rat central nervous system. Immunohistochemical staining revealed the localization of NUCB2/nesfatin-1 in the piriform and insular cortex, endopiriform nucleus, nucleus accumbens, lateral septum, bed nucleus of stria terminalis, central amygdaloid nucleus, medial preoptic area, dorsal raphe nucleus, ambiguus nucleus, ventrolateral medulla and gigantocellular reticular nucleus, as well as Purkinje-cells of the cerebellum. In the spinal cord, nesfatin-1 immunoreactivity (IR) was found in both sympathetic and parasympathetic preganglionic neuronal groups and in the dorsal area X from lower thoracic to sacral segments. The immunohistochemical results were confirmed by RT-PCR in the central amygdaloid nucleus, nucleus accumbens, cerebellum and lumbar spinal cord microdissected by punch technique. The features and distributions of nesfatin-1 IR and mRNA expression in the brain and spinal cord suggest that NUCB2/nesfatin-1 could play a wider role in autonomic regulation of visceral-endocrine functions besides food intake.     

Learning- and cerebellum-dependent neuronal activity in the lateral pontine nucleus

The effects of inactivation of cerebellar deep nuclei and the lateral pontine nucleus on classical eyeblink conditioning with tone or lateral reticular nucleus (LRN) stimulation as conditioned stimuli (CSs) were examined. Inactivation of cerebellar deep nuclei abolished eyeblink conditioned responses (CRs) when the CS was either a tone or LRN stimulation. Inactivation of the lateral pontine nucleus prevented only the acquisition and retention of tone-evoked eyeblink CRs. Multiple-unit recording demonstrated that when LRN stimulation was used as the CS, inactivation of the interpositus nucleus abolished learning-related neuronal activity in the lateral pontine nucleus, whereas inactivation of pontine nucleus had little effect on similar activity in the interpositus nucleus. Thus, the learning-induced neuronal activity in the lateral pontine nucleus was most likely driven by the cerebellar interpositus nucleus.     

Inhibitory control of intracerebellar nuclei by the Purkinje cell axons

Summary In anaesthetized cats, synaptic events in cerebellar nuclei neurones were investigated with intracellular microelectrode techniques. These cells were identified by their antidromic activation along their axons and/or by their location in histological sections. In the cells of lateral nucleus IPSPs were induced monosynaptically during stimulation of the overlying hemispheral cortex of the cerebellum. In the cells of nuclei interpositus and fastigii, similar IPSPs were produced from the paravermal and vermal cortices, respectively. The postulate that the Purkinje cells exert an inhibitory action upon their target neurones thus applies not only to Deiters neurones, as previously proposed, but also to cells in the cerebellar nuclei. Stimulation of the cerebellar afferents at the inferior olive, the pontine nucleus and the lateral reticular nucleus produced EPSPs in cerebellar nuclei cells with relatively brief latencies, probably through axon collaterals of these afferents. The EPSPs were followed by IPSPs and slow depolarizations of disinhibitory nature, which, as studied previously in Deiters neurones, might be caused respectively by activation and subsequent depression of Purkinje cells through the cerebellar intracortical mechanisms.     

Co-localization of nitric oxide synthase and choline acetyltransferase in the brain of the goldfish (Carassius auratus)

This work investigates the nitrergic and cholinergic systems in the brain and spinal cord of the goldfish (Carassius auratus). We studied the immunohistochemical localization of antibodies against the neuronal nitric oxide synthase (nNOS) and choline acetyltransferase (ChAT) by bright-field and confocal microscopy. Nitrergic and cholinergic cells were segregated within the telencephalon, in both dorsal and ventral areas, and co-distributed in some nuclei of the diencephalon, mesencephalon, rhombencephalon, and spinal cord. Double-labeling experiments revealed nNOS/ChAT-positive cells in (1) the diencephalon: the preoptic and suprachiasmatic nuclei, the habenula, the dorsal thalamus, and the nucleus of the medial longitudinal fasciculus; (2) the mesencephalon: the optic tectum, the mesencephalic portion of the trigeminal nucleus, the oculomotor and trochlear nuclei, and the Edinger-Westphal nucleus; and (3) the rhombencephalon: the secondary gustatory nucleus, the nucleus isthmi, the lateral lemniscus nucleus, the cerebellum, the reticular formation, different nuclei of the octaval column, the motor zone of the vagal lobe, and the trigeminal, facial, abducens, glosso-pharyngeal, vagal, and hypobranchial motor nuclei. Double-labeled cells were also observed in the spinal motor column. The percentage of double-labeled cells was different in each studied nucleus, indicating a selective distribution pattern. Because double-labeled cells were more abundant in those nuclei involved with sensory and motor physiological processes, we suggest the involvement of both nitric oxide and acetylcholine in these neural functions in fish.     

Expression of pannexin1 in the CNS of adult mouse: cellular localization and effect of 4-aminopyridine-induced seizures

The expression pattern of pannexin1, a gene coding for a protein that forms gap junction channels, was studied as both mRNA and protein in the CNS of adult mouse. Pannexin1 was widely expressed in the CNS by neuronal cell types but not glial cells, except for Bergmann glial cells of the cerebellar cortex. Cells positive to Ca-binding proteins, principally parvalbumin, but also calbindin and calretinin, as well as glutamate decarboxylase 67 kDa isoform, were pannexin1-positive. Pannexin1 labeling was found in cells which are known to exhibit spontaneous and synchronous discharge, such as neurons of the inferior olivary complex and the reticular thalamic nucleus, and also in neurons whose electrical activity is not coupled with neighboring cells, such as motoneurons of the spinal cord. The analysis of cellular localization showed puncta that surrounded cell bodies (e.g. the pyramidal cells of hippocampus) or restricted areas inside the cell bodies (e.g. the spinal motoneurons). In Bergmann glial cells the staining was present as fine grains that covered a large part of the cellular surface. Pannexin1 stained cells that previous studies have reported as expressing connexin36, another protein forming gap junction channels. Thus, it was possible that these two proteins could be integrated in the same functions. Since connexin36 expression levels change after seizures, we examined the expression of both pannexin1 and connexin36 in cerebral cortex, hippocampus, cerebellum and brain stem at different time intervals (2, 4 and 8 h) after i.p. injection of 4-aminopyridine, which resulted in systemic seizures. The only modification of the expression levels observed in this study concerned the progressive decrement of the connexin36 in the hippocampus, while pannexin1 expression was unchanged. This finding suggested that pannexin1 and connexin36 are involved in different functional roles or that they are expressed in different cell types and that only those expressing the Cx36 are induced to apoptosis by epileptic seizures.     

Further studies on the fiber connections of the central cervical nucleus in the cat

Summary The course and cerebellar termination of the axons of the cells in the central cervical nucleus (CCN) was studied in five cats after injections of wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) into the C1-4 segments involving the CCN. In two cats a hemisection was performed ipsilateral to and above the injections in order to prevent transport of WGA-HRP from cerebellar-projecting neurons in lamina VI, just dorsal to the CCN. Labeled axons were found in the brain stem contralateral to the injections just lateral to the spinal trigeminal tract and the vestibular nuclei, and in the reticular formation. Some fibers terminated in the vestibular nuclei (especially group x), the reticular formation, and the inferior olive. The axons entered the cerebellum via the superior cerebellar peduncle. In the cerebellum mossy fiber terminals were found bilaterally in the deep vermal parts of lobules I–VIII. Only in cases without lesions were terminals found in the paramedian lobule ipsilateral to the injection, suggesting that neurons in lamina VI, but not in the CCN, project to the paramedian lobule. In the brain stem retrogradely labeled neurons (possible afferents to the CCN) were found in the vestibular (lateral, inferior and medial) nuclei, the reticular formation, and the trigeminal (spinal and mesencephalic) nuclei. The cerebellar distribution of mossy fiber terminals suggests that spinocerebellar fibers from lower parts of the spinal cord passing through the injection area do not transport WGA-HRP to their terminals.     

Synaptic action of the fastigiobulbar impulses upon neurones in the medullary reticular formation and vestibular nuclei

Summary In anaesthetized cats, the fastigial nucleus of cerebellum was stimulated with electric pulse currents, and the effects thereby induced were investigated by recording intracellularly from cells in the medullary reticular formation, the nucleus of Deiters and the descending vestibular nucleus. The early effect commonly seen in these cells was initiation of excitatory postsynaptic potentials (EPSPs) with monosynaptic latencies from both sides of the fastigial nuclei. These EPSPs appeared to be produced in part by a kind of axon reflex through cerebellar afferent fibres, but a certain portion of them was ascribable to the crossed fastigiobulbar axons, as they were influenced by stimulation of the cerebellar cortex in the manner to be expected from the previous study on cerebellar nuclei. These EPSPs were followed by a sequence of a prolonged disfacilitatory hyperpolarization and a late facilitatory depolarization, which apparently reflected the inhibition and disinhibition, respectively, produced in fastigial neurones via Purkinje cell axons of the corticonuclear projection. Either EPSPs or IPSPs were also induced in both reticular and vestibular neurones through polysynaptic pathways in which the fastigiobulbar projection might have been involved.     

Ontogeny of the calcium binding protein parvalbumin in the rat nervous system

Summary In the adult rat brain, the calcium-binding protein parvalbumin is preferentially associated with spontaneously fast-firing, metabolically active neurons and coexists with gamma-amino-butyric acid (GABA) in cortical inhibitory interneurons. Whether this is so in developing neurons has not been explored. To this end, we have used parvalbumin immunohistochemistry to study expression of this protein in the rat nervous system during pre- and postnatal life. Our results indicate that parvalbumin first appears at embryonic day 13 in sensory system of the spinal cord, in the vestibular (VIII), the trigeminal (V) and the visuomotor (III, IV VI) systems, and develops rapidly during the following days. In these locations the expression of parvalbumin coincides with the beginning of physiological activity in nerve cells. In the gamma-aminobutyric acid (GABA)-containing interneurons of the cerebral cortex and the hippocampus, as well as in the Purkinje cells of the cerebellum, parvalbumin only appears postnatally. It lags behind the development of GABA-immunoreactivity by 1 to 2 weeks. The beginning of its expression, in the cerebellum at least, coincides with the arrival of excitatory synaptic input and the onset of spontaneous activity. Thus, during the development of the nervous system, the expression of parvalbumin is subordinate to the establishment of physiological activity.Abbreviations 3 oculomotor nucleus - 4 trochlear nucleus - 4n trochlear nerve - 6 abducens nucleus - 12 hypoglossal nucleus - 3n oculomotor nerve - 4V 4th ventricle - 5g trigeminal ganglion - 5n trigeminal nerve - 5mx trigeminal nerve, maxillary branch - 8c1 cochlear ganglion - 8g vestibular ganglion - 8n vestibular nerve - 10n vagal nerve - Amb ambiguus nucleus - CaBP calcium-binding protein - Ce cerebellum - ChP choroid plexus - cl cochlea - CPu caudate putamen - Cu cuneate nucleus - Cx cerebral cortex - df dorsal funiculus spinal cord - dr dorsal root spinal nerve - E15 embryonic day 15 of gestation - ECN external cuneate nucleus - Fr formatio reticularis - GABA gamma-amino-butyric acid - GAD glutamate decarboxylase - gl granular layer cerebellum - Gr gracile nucleus - Hip hippocampus - H heart - inc inferior colliculus - IOK inferior olive, kap cooy medial nucleus - Li liver - LMol lacunosum moleculare layer hippocampus - Lu lung - LV lateral ventricle - LVe(v) lateral vestibular nucleus (ventral) - LVe(d) lateral vestibular nucleus (dorsal) - me5 mesencephalic trigeminal tract - Me5 mesencephalic trigeminal nucleus - Mes mesencephalon - ml molecular layer cerebellum - MVe medial vestibular nucleus - Or oriens layer hippocampus - P 2 postnatal day 2 - Pu Purkinje-cell layer, cerebellum - Py pyramidal cell layer, hippocampus - R red nucleus - Rhom rhombencephalon - Rt reticular thalamic nucleus - sk skin - sn substantia nigra - spgl spinal ganglion - sp5 spinal trigeminal tract - SpVe spinal vestibular nucleus - Sp5I spinal trigeminal nucleus, interpolar - suc superior colliculus - SuVe superior vestibular nucleus - TBS tris-buffered saline - tch tactile hair sinus - ve vestibular epithelium - vb vertebral body - vh ventral horn spinal cord - VL ventrolateral thalamic nucleus - VP ventral pallidum - vr ventral root spinal nerve     

A temporal analysis of the origin and distribution of serotoninergic afferents in the cerebellum of pouch young opossums

Summary In the present study, a temporal analysis of the pattern of distribution of serotoninergic fibers and varicosities within the cerebellum of pouch young opossums was carried out. Particular attention was focused on animals ranging in age from postnatal day (PD) 21-PD 72, because there is a transient expression of serotonin immunoreactivity in the cerebellar cortex during that interval. Between PD 1–33, there is a progressive increase in serotoninergic immunoreactivity throughout the cerebellar cortex. After PD 33, there is a decrease in the relative number of immunostained fibers followed by a reorganization into the adult pattern of distribution.A double labeling paradigm, in which horseradish peroxidase, used as a retrograde marker, combined with serotonin immunohistochemistry was employed to localize serotoninergic neurons that project to the developing cerebellum. Initially (PD 9), serotoninergic cells in the medullary reticular formation and dorsolateral pontine tegmentum are double labeled. After PD 77, only neurons in the medullary reticular formation were double labeled.The course taken by serotoninergic axons from the brainstem to the cerebellum also was analyzed. Between PD 1 and PD 42, serotoninergic axons enter the cerebellum via four different routes: 1) the inferior cerebellar peduncle; 2) a pathway located lateral and rostral to the inferior cerebellar peduncle; this bundle of serotonin axons contains immunoreactive fibers that also enter the tectum (this tract is referred to as the tecto-cerebellar bundle in this report); 3) the medial aspect of the superior cerebellar peduncle; and 4) the tela choroidea. After PD 40, the latter two pathways are the primary routes by which serotoninergic fibers enter the cerebellum. The loss of serotoninergic fibers in the first two pathways coincides with the decrease in serotoninergic immunoreactivity seen in the cerebellar cortex described above.In summary, the results suggest that the serotoninergic projection to the opossum's cerebellum is remodelled during development. It is proposed that the serotonin fibers present at early stages of development may play a role in regulating specific events in cerebellar maturation. In contrast, the serotoninergic axons which have a more restricted pattern of distribution later in development, and in the adult, likely modulate neuronal activity within the cerebellum.Abbreviations BP basilar pons - CB cerebellum - CF cephalic flexure - CN cerebellar nuclei - CRI crus I - CRII crus II - DAO dorsal accessory olive - DN dentate nucleus - EGL external granule cell layer - F flocculus - FP primary fissue - ICP interior cerebellar reduncle - IO inferior olive - IOC inferior olivary complex - IV fourth ventricle - LS lobus simplex - MCP middle cerebellar peduncle - MED medulla - MID midbrain - PF pontine flexure - PFL paraflocculus - PML paramedian lobule - PN pontine nuclei - PT pontine tegmentum - RA raphe - RGc _v nucleus reticularis gigantocellularis pars ventralis - SO superior olive - SV superior medullary velum - TC tela choroidea - TE tectum - VII facial nucleus - Roman numerals I–X cerebellar lobules     

Expression of serotonin2A receptors in Purkinje cells of the developing rat cerebellum

Previous physiological and pharmacological studies have shown that the serotonin_2A (5-HT_2A) receptor is involved in cerebellar functions. However, the expression of 5-HT_2A receptors in the developing cerebellum has not been elucidated to date. In the present immunohistochemical study, we examined developmental changes of the distribution of 5-HT_2A receptors in Purkinje cells of the rat cerebellum from embryonic day 18 (E18) to postnatal day 21 (P21). The weak immunoreaction to 5-HT_2A receptors was found in the deep cerebellar nuclei on E19. In the cerebellar cortex of the hemisphere and the posterior vermis, somata of Purkinje cells became weakly immunoreactive on P0. With the dendritic elongation and arborization, the immunoreaction appeared in the proximal parts of Purkinje cell dendrites. Distal parts of the dendrites became immunoreactive after P12, and were strongly immunolabeled by P21. The present study may provide a structural basis to investigate the roles of 5-HT_2A receptors during the cerebellar development.     

Fos expression in serotonergic neurons in the rat brainstem following noxious stimuli: an immunohistochemical double-labelling study

In order to detect whether there were different expression patterns of Fos protein induced by somatic or visceral noxious stimulation in the serotonergic neurons in the rat brainstem, an immunohistochemical double-labelling technique for serotonin (5-HT) and Fos was employed after subcutaneous or stomach injection of formalin. The two stimuli were matched in pilot experiments to produce maximum Fos expression. The expression of Fos protein in 5-HT-containing neurons (5-HT/Fos co-localized neurons) could be observed in the ventrolateral subdivision of the midbrain periaqueductal grey, interpeduncular nucleus, paramedian raphe nucleus, all of the brainstem raphe nuclei, the alpha part of the gigantocellular reticular nucleus and the lateral paragigantocellular reticular nucleus. The locations of the 5-HT/Fos co-localized neurons in the brainstem of animals subjected to somatic noxious stimulation were similar to those subjected to visceral noxious stimulation. However, the number and proportion of the 5-HT/Fos co-localized neurons in the median raphe nucleus and nucleus raphe obscurus of the rat subjected to visceral noxious stimulation were statistically greater than those in rats subjected to somatic noxious stimulation. These results suggest that serotonergic neurons in median raphe nucleus and nucleus raphe obscurus have a tendency to higher neuronal activity after visceral noxious stimulation.     

5-Hydroxytryptamine and Dopamine Neurons in the Cerebellum of the New-Hatching Yangtze Alligator Alligator sinensis

Nissl and immunohistochemical staining methods were used to morphologically characterize the cerebellum of the new-hatching Yangtze alligator, and the cerebellar histological structure and the distribution profiles of 5-hydroxytryptamine (5-HT) and dopamine (DA) neurons were investigated for the first time. The results of cerebellar histological structure showed that there was a ventriculus cerebelli in the cerebellum of the new-hatching Yangtze alligator, the surface of the cerebellar cortex was not very smooth, the cerebellar cortex could be divided into four layers, which include external granular layer, molecular layer, Purkinje cell layer and granular layer, Purkinje cell layer could be characterized specially by multilayer, two cerebellar nuclei termed as the nucleus cerebelli lateralis and the nucleus cerebelli medialis were found in the cerebellar medulla. 5-hydroxytryptamine-immunoreactive (5-HT-IR) and dopamine-immunoreactive (DA-IR) neurons and fibers distributed widely in the cerebellum. The structures and profiles of 5-HT-IR and DA-IR neurons and fibers in the cerebellum of the Yangtze alligator were similar to that reported in other reptiles, but also had some specific features. The abundance of 5-HT and DA in cerebellum suggested that these highly conserved neurotransmitters would play important roles in motor control. Anat Rec, 302:861–868, 2019. © 2018 Wiley Periodicals, Inc.