Single-labeled Neurons Research Articles

Co-localization of 5-HT(1B/1D/1F) receptors and glutamate in trigeminal ganglia in rats.

Anti-migraine triptan drugs are 5-HT(1B/1D) receptor agonists which are thought to block the neurotransmitter/neuropeptide release from sensory nerve terminals and directly constrict blood vessel smooth muscles. In the present study, we have investigated the anatomical basis for a possible modulation of glutamate release from trigeminal ganglion neurons by 5-HT(1B/1D) receptor agonists and by 5-HT1F receptor agonists, using double immunohistochemical staining technique in the rat. The majority of 5-HT1B, 5-HT1D or 5-HT1F receptor positive neurons were also glutamate positive, but both 5-HT1B, 5-HT1D or 5-HT1F receptor single-labeled and glutamate single-labeled neurons were observed. These results suggest that 5-HT(1B/1D/1F) receptor agonists may modulate glutamate release, and that one mechanism of their anti-migraine action could be the blockade of glutamate release.

Definite segregation of cortical neurons projecting to the dorsal column nuclei in the rat.

The dorsal column nuclei (DCN) receive a substantial contingent of projections that arise from a number of somatosensory and motor cortical areas. We investigated the spatial organization of these projections in the rat by placing small deposits of two retrograde fluorescent tracers in adjacent foci within the DCN. Single-labeled neurons were abundant in layer V of the primary somatosensory (SI) and motor areas, and in the posterior parietal cortex. More sparse labeling was found in the medial agranular cortex (or MII), and the second somatosensory area. A somatotopic-like arrangement of these neurons was more clearly noticed in the granular zones of SI. Double-labeled neurons were very uncommon, and appeared at border regions where single-labeled cells intermingled. The segregation of these projections supports some differential modulatory effects that the cortex exerts on the somatosensory processing that takes place in the DCN.

Identification of branching paraventricular neurons of the hypothalamus that project to the rostroventrolateral medulla and spinal cord

The paraventricular nucleus of the hypothalamus has efferent connections to autonomic nuclei known to ultimately regulate cardiovascular function. Studies have revealed projections to the sympathetic preganglionic neurons of the spinal cord and presympathetic motor neurons of the rostral ventrolateral medulla. This study set out to establish whether the same neurons in the paraventricular nucleus innervate both these regions. In rats the fluorescent neuroanatomical tracers FluoroGold, Fast Blue or Dextran tetramethyl rhodamine were injected into either the rostral ventrolateral medulla or T2 region of the spinal cord. After a suitable survival period (five to seven days) three populations of neurons could be identified in the paraventricular nucleus, double-labelled neurons and single-labelled neurons resulting from the injections into the spinal cord or injections into the rostral ventrolateral medulla. The neurons were of similar size regardless of the dye content. Most neurons were found in the parvocellular subdivision of the mid rostral paraventricular nucleus. The number of labelled neurons decreased in the caudal sections. This study provides an anatomical basis for three means of influence that the paraventricular nucleus can have on sympathetic activity; a hierarchical in series projection via the rostral ventrolateral medulla; a projection running in parallel with this but bypassing the rostroventrolateral medulla; and a branching population innervating neurons in both the rostral ventrolateral medulla and spinal cord. The paraventricular nucleus of the hypothalamus is an important brain area concerned with maintaining cardiovascular homeostasis. This anatomical study has not only provided confirmatory evidence that direct projections arising from the paraventricular hypothalamic nucleus do project to the rostral ventrolateral medulla and spinal cord, regions known to influence cardiovascular regulation. The study has identified a branching projection originating in the paraventricular nucleus of the hypothalamus that projects to both the rostral ventrolateral medulla and the spinal cord. Thus the paraventricular nucleus of the hypothalamus has three pathways in which to influence cardiovascular homeostasis.

NADPH-Diaphorase-containing neurons in the medullary structures involved in generation of the respiratory activity in neonatal rats

Using a histochemical technique, we examined distribution of the neurons containing a marker of nitric oxide synthase (NOS), NADPH-diaphorase (NADPH-d), on frontal slices of the medulla and upper cervical spinal segments of 4-day-old rats. It was demonstrated that NADPH-d-positive cells are present within the dorsal and ventral medullary respiratory groups. The highest density of the labeled middle-size multipolar neurons (27.9±2.6 cells per 0.1 mm2 of the slice) was observed in the rostral part of the ventral respiratory group, within the reticular lateral paragigantocellular nucleus. Similar NADPH-d-positive neurons were also observed in other reticular formation structures: rostroventrolateral reticular, gigantocellular, and ventral medullary nuclei, and in the ventral part of the paramedial nucleus. There were no labeled neurons in the lateral reticular nucleus. Single small and medium-size labeled neurons were found at all rostro-caudal levels of thenucl. ambiguous (nuclei retrofacialis, ambiguous, andretroam-biguous). Groups of NADPH-d-positive neurons were also revealed within the dorsal respiratory group, along the whole length of thenucl. tractus solitarii (mostly in its ventrolateral parts). Single labeled neurons were also observed in thenucl. n. hypoglossi, and their groups were observed in the dorsal motor part of thenucl. n. vagus. Involvement of the structures containing NADPH-d-positive neurons in the processes related to generation of the respiratory activity is discussed. Our neuroanatomical experiments prove that in early postnatal mammals NO is actively involved in generation and regulation of the medullary respiratory rhythm.

Colocalization of arginine-vasotocin and chicken luteinizing hormone-releasing hormone-I (cLHRH-I) in the preoptic–hypothalamic region of the chicken

To characterize a possible relationship between chicken luteinizing hormone-releasing hormone-I (cLHRH-I) and arginine-vasotocin (AVT) we performed immunocytochemical double-stainings throughout the preoptic–hypothalamic region of the chicken brain. This study clearly reveals a partial colocalization between both neuropeptides. Single-labeled neurons, containing either cLHRH-I or AVT are found intermingled with double stained cells, immunoreactive (ir) for both peptides. A significant number of double-labeled perikarya is found in the preoptic area, more specifically in the ventral and external portion of the supraoptic nucleus (SOv and SOe) and in the medial preoptic nucleus (MPOv). At the level of the anterior hypothalamus, double-labeled cells are predominantly observed near the third ventricle in the nucleus paraventricularis magnocellularis (PVN) and the nucleus periventricularis hypothalami (PHN). Next to this colocalization, a number of cLHRH-I-ir cell bodies are found in close apposition to AVT-ir fiber profiles in the very same areas. Taken together, these data are the first to provide morphological evidence indicating that the AVT system might be involved in the regulation of cLHRH-I release and thus of reproductive functions in birds.

Nitric oxide synthase-containing projections to the ventrobasal thalamus in the rat.

Microiontophoretic studies of thalamic neurons suggests that nitric oxide (NO) plays an important role in mediating somatosensory transmission. The thalamus contains few nitric oxide synthase (NOS)-immunoreactive neurons; thus, the major source of thalamic NO is presumably from NOS-positive axons of extrathalamic origin. The cells of origin of these putative NOS-containing pathways to the ventrobasal thalamus were investigated in rats by combining retrograde tracing with immunocytochemistry for NOS. The location and morphology of double-labeled neurons was compared with that of single-labeled neurons. The most significant sources of NOS-containing afferents to the thalamus were found to be the pedunculopontine (PPN) and laterodorsal tegmental (LDT) nuclei. NOS-immunoreactive neurons in these cholinergic nuclei project bilaterally to the thalamus, most strongly ipsilaterally. The thalamus appears to be a major target of PPN, since even selective thalamic injections result in retrograde labeling of at least one third of its NOS-immunoreactive neurons. A significant number of NOS-negative neurons in both the PPN and LDT also project to the thalamus. Minor sources of NOS-containing thalamic afferents include the lateral hypothalamus, the dorsal, median and pontine raphe nuclei, the parabrachial nuclei, and the pontomedullary reticular formation. In all these structures, NOS-negative thalamopetal neurons greatly outnumber the NOS-positive ones. Ascending sensory pathways to the thalamus, including those from the sensory trigeminal nuclei, the dorsal column nuclei, and the spinal cord, as well as the auditory and vestibular centers, arise exclusively from NOS-negative neurons. The major NOS-positive projections are implicated in affective and alerting systems, supporting that NO may act to modulate attentiveness in thalamic relay nuclei.

Origin of noradrenergic afferents to the shell subregion of the nucleus accumbens: anterograde and retrograde tract-tracing studies in the rat

The nucleus accumbens (NAcc) can be subdivided into `core' and `shell' based on anatomical connections and histochemical markers. Previous studies have demonstrated dopamine-β-hydroxylase immunoreactive (DBH-ir) fibers in the NAcc shell, but the source of these noradrenergic (NE) afferents has not been determined. Therefore, we have investigated in detail the anatomy of NE afferents to this subregion. Dual immunohistochemistry for DBH and substance P demonstrated numerous DBH-ir fibers in the caudal NAcc shell. Neurons projecting to the NAcc were identified with Fluoro-Gold (FG) or cholera toxin B (CTb) retrograde tracing and tyrosine hydroxylase (TH) immunohistochemistry. Single- and double-labeled neurons were observed in the A2 and A1 NE cell groups following FG injections into the caudal NAcc shell. Numerous FG and CTb single-labeled neurons were found in the rostral locus coeruleus (LC), subcoeruleus and pericoerulear dendritic region, with an occasional double-labeled neuron in the LC. Few labeled neurons were seen in the brainstem after FG injections into the NAcc core, consistent with the lack of DBH-ir in this subterritory. To confirm these results, injections of Phaseolus vulgaris leucoagglutinin or biotinylated dextran amine were made into the LC or nucleus tractus solitarius (NTS). Virtually no labeled fibers were observed in the NAcc following injections into central LC. However, fibers were observed in the NAcc shell after injections in the NTS. These results indicate that the primary source(s) of NE afferents to the NAcc shell is the A2 region of the NTS, with lesser contributions from A1 and LC.

Cerebellar and spinal projections of the coeruleus complex in the duck: A fluorescent retrograde double-labeling study

The double fluorescent retrograde tracing technique was used to identify, within the coeruleus complex (Co complex) of the duck, the nerve cells projecting to the cerebellar cortex and to the spinal cord. This technique was also used to investigate the possibility that the cerebellar and spinal projections of the Co complex are collaterals of the same axons. In the same animal, nuclear Diamidino yellow dihydrochloride (DY) fluorescent tracer was placed into the cerebellar cortex of folia V-VII, and cytoplasmic fluorescent Fast blue (FB) dye was injected into C3-C4 spinal cord segments. FB labeled multipolar somata and DY fluorescent nuclei were intermingled within the dorsal caudal region of the locus coeruleus (LCo) and within the dorsal division of the nucleus subcoeruleus (dSCo). Moreover, in the LCo, a low proportion of double-labeled neurons (about 3-4% of labelings) was evidenced among single-labeled neurons. In the ventral division of the nucleus subcoeruleus (vSCo), occasional DY labeled nuclei were found, whereas FB-labeled cells were frequently present. The present findings reveal the location of the coeruleocerebellar and coeruleospinal projecting neurons within the Co complex of the duck. They are intermingled in the caudal portion of the LCo and along the rostrocaudal extent of the subjacent dSco. The LCo and the dSCo are the major source of the projections to the folia V-VII, whereas the vSCo contributes very slightly to the innervation of the cerebellar injected areas. Moreover, the double-labeling study demonstrates that in the duck a low percentage of neurons within the ventrolateral portion of the caudal region of the LCo projects both to the cerebellar cortex of folia V-VII and to C3-C4 spinal cord segments via collaterals. Therefore, these neurons simultaneously influence the cerebellar cortex and spinal cord. The possibility that the projections studied are noradrenergic and that they play a role in feeding is discussed.

Postnatal development of somatostatin- andneuropeptide y-immunoreactive neurons in rat cerebralcortex : a double-labeling immunohistochemical study

The postnatal development of somatostatin (SOM)- and neuropeptide Y(NPY)-immunoreactive (ir) neurons was examined in rat cerebral cortex, while considering theircoexistence in cortical neurons. Using double immunohistochemical staining for SOM and NPYwith diaminobenzidine and benzidine dihydrochloride as chromogens, we subdividedimmunoreactive cells into double-labeled SOM/NPY-, SOM only-, and NPY only-ir neurons.SOM/NPY- and SOM only-ir neurons were detectable even at the day of birth, in contrast toNPY only-ir cells which first appeared in most cortices from week two. The morphologicalfeatures of double-labeled SOM/NPY neurons differed with those of SOM only- and NPYonly-ir neurons. No apparent changes in the shape and size of single-labeled neurons occurredwith age ; throughout their postnatal life they were round and ovoid, had a thin rim ofperinuclear cytoplasm, and short processes. However, the features of SOM/NPY-ir neurons werenot consistent according to postnatal age ; by day P7, these neurons showed immature featuresand they began to show more advanced neuronal characteristics by week P2, when they had alarger and more intensely-stained cytoplasm. In addition, their processes were longer, thicker andmore complex than at earlier ages. At this age, SOM/NPY-ir somata were close to their nearmaximum size. From week P4, they became smaller and were lightly labeled. SOM/NPY-irsomata were larger than SOM only- and NPY only-ir somata at and after two weeks of age. Thepresent results, showing different postnatal maturation patterns such as time of appearance andmorphological features, raise the possibilities that double-labeled SOM/NPY and single-labeledimmunoreactive neurons may be different populations regulated by different mechanisms in theirdevelopment, and with different functional properties during development.

Localization of parvalbumin, calretinin, and calbindin D-28k in identified extraocular motoneurons and internuclear neurons of the cat.

Calcium-binding proteins have been shown to be excellent markers of specific neuronal populations. We aimed to characterize the expression of calcium-binding proteins in identified populations of the cat extraocular motor nuclei by means of immunohistochemistry against parvalbumin, calretinin, and calbindin D-28k. Abducens, medial rectus, and trochlear motoneurons were retrogradely labeled with horseradish peroxidase from their corresponding muscles. Oculomotor and abducens internuclear neurons were retrogradely labeled after horseradish peroxidase injection into either the abducens or the oculomotor nucleus, respectively. Parvalbumin staining produced the highest density of immunoreactive terminals in all extraocular motor nuclei and was distributed uniformly. Around 15-20% of the motoneurons were moderately stained with antibody against parvalbumin, but their axons were heavily stained, indicating an intracellular segregation of parvalbumin. Colchicine administration increased the number of parvalbumin-immunoreactive motoneurons to approximately 85%. Except for a few calbindin-immunoreactive trochlear motoneurons (1%), parvalbumin was the only marker of extraocular motoneurons. Oculomotor internuclear neurons identified from the abducens nucleus constituted a nonuniform population, because low percentages of the three types of immunostaining were observed, calbindin being the most abundant (28.5%). Other interneurons located within the boundaries of the oculomotor nucleus were mainly calbindin-immunoreactive. The medial longitudinal fascicle contained numerous parvalbumin- and calretinin-immunoreactive but few calbindin-immunoreactive axons. The majority of abducens internuclear neurons projecting to the oculomotor nucleus (80.7%) contained calretinin. Moreover, the distribution of calretinin-immunoreactive terminals in the oculomotor nucleus overlapped that of the medial rectus motoneurons and matched the anterogradely labeled terminal field of the abducens internuclear neurons. Parvalbumin immunostained 42% of the abducens internuclear neurons. Colocalization of parvalbumin and calretinin was demonstrated in adjacent semithin sections, although single-labeled neurons were also observed. Therefore, calretinin is proven to be a good marker of abducens internuclear neurons. From all of these data, it is concluded that parvalbumin, calretinin, and calbindin D-28k selectively delineate certain neuronal populations in the oculomotor system and constitute valuable tools for further analysis of oculomotor function under normal and experimental conditions.

Axonal transport of fluorescent carbocyanine dyes allows mapping of peripheral nerve territories in gingiva.

Sensory innervation of gingival tissue can cause neurogenic inflammation that depends on the extent of the branching area of the peripheral nerve fibers. We designed the present study to determine whether single trigeminal axons branch to both the buccal and palatal gingiva of maxillary molars of adult rats. Accumulation via retrograde transport of DiI (red) or DiA (green) fluorescent carbocyanine dyes in neurons of trigeminal ganglia was evaluated 7 days after applying one dye to the buccal sulcus and the other to the palatal sulcus. Both dyes were absorbed through the junctional epithelium, and the two sites each labeled similar numbers and sizes of neurons in the lateral zone of the maxillary division (44% from buccal and 46% from palatal gingiva). Double-labeled neurons had the same size (32.5 +/- 6.70 microns, mean circumference +/- S.D.) and location as single-labeled neurons, and they were 9% of the total. This study shows that exogenous dyes can diffuse into mucosa and thereby allow in vivo mapping of sensory nerve branching patterns to several intact tissues per animal. We found that 9% of the labeled cells extended to both the buccal and palatal gingiva. Thus, inflammation that spreads from one gingival region to the other could have a neurogenic mechanism involving trigeminal sensory neurons that extend their peripheral branches to innervate both buccal and palatal gingiva of adult rat molars.

Intrastriatal Infusions of Brain-Derived Neurotrophic Factor: Retrograde Transport and Colocalization with Dopamine Containing Substantia Nigra Neurons in Rat

The pattern of retrogradely transported BDNF, a member of the nerve growth family of neurotrophins, following intrastriatal infusion was immunohistochemically visualized within the rodent central nervous system. Human recombinant BDNF was infused at a rate of 3 μg/h for 7 days with an Alzet 2002 minipump prior to sacrifice. Tissue immunohistochemically processed using a turkey anti-BDNF antibody revealed retrogradely transported BDNF within neurons located mainly within the ipsilateral frontoparietal cortex (predominantly layer V), parafascicular and posterior thalamic nuclei, and substantia nigra, pars compacta. Sections dual immunoreacted for BDNF and tyrosine hydroxylase revealed a subpopulation of dopaminergic neurons (approximately 28%) within the pars compacta which contained retrogradely transported BDNF. Experiments in which a mixture of BDNF and the retrograde tracer fluorogold were simultaneously infused for 7 days into the striatum revealed BDNF and fluorgold single-labeled neurons as well as BDNF and fluorogold dual-labeled cells within the substantia nigra, pars compacta. These observations indicate that only a subpopulation of neurons within the substantia nigra retrogradely transport BDNF following intrastriatal infusion and thus only a subpopulation of cells may be responsive to the trophic influences of BDNF. The retrograde transport of trophins, such as BDNF, represents a unique neuroanatomical tool to selectivity map the location of specific neurotrophin-responsive systems. Unraveling the trophic anatomy of BDNF will aid in understanding its role in development, degeneration, and experimental animal models of regeneration providing essential data for its use in clinical neurodegenerative disorders including Parkinson's disease.

Transient ipsilateral innervation of the cerebellum by developing olivocerebellar neurons. A retrograde double-labelling study with fast blue and diamidino yellow

In neonatal rats the injection of Fast Blue and Diamidino Yellow retrograde fluorescent tracers, each into separate cellebellar hemispheres, reveals the presence of double-labelled neurons positioned bilaterally in the inferior olivary complex during the early postnatal period (postnatal day 0 to postnatal day 5). This suggests that those neurons whose axons are able to take up both tracers project to both hemicerebella during this period of postnatal development. Double-labelled neurons were observed in one-and five-day-old injected postnatal rats, but were absent in older animals (10 and 30 days old). The presence of these neurons coincides with a transient period of poly-innervation of Purkinje cells by climbing fibres. They may thus be participating in transitory interactions preceding the formation of definitive climbing fibre synaptic arrangements in the cerebeller cortex. The technique employed is unable to clearly define the pathway of this transient olivocerebellar projection into the ipsilateral cerebellum; however, in direct evidence—like the topographic distribution of double-labelled neurons relative to tracer injection sites, and the small number of single-labelled neurons within the ipisilateral olivary complex, together with previous data on the axonogenesis of olivary neurons [ Bourrat and Sotelo (1988) Devl Brain Res. 39, 19–37]—suggests that these fibres reach the cerebellum through the contralateral inferior cerebellar peduncle and give rise to collaterals, some of which subsequently decussate again within the cerebellum. These fibres probably represent transient collaterals of the normally contralateral olivocerebellar fibres that cross the cerebellar midline and reach mirror-image loci within the ipsilateral hemicerebellum.

Distribution of bulbospinal neurons supplying bilateral innervation to the phrenic nucleus in the rat

The location of bulbospinal neurons with axon collaterals in both phrenic nuclei were determined by injecting two different fluorescent tracers into the right and left C4 cervical spinal cord. In contrast to single-labeled neurons that were found throughout the rostrocaudal extent of the medulla, the majority of double-labeled neurons were located in the rostral ventral respiratory group. Only a few double-labeled neurons were found in the ventrolateral nucleus of the solitary tract. The role of this bilateral pathway in synchronizing the activity of the phrenic nucleus is discussed.

Laterality in the vestibulo-cerebellar mossy fiber projection to flocculus and caudal vermis in the rabbit: A retrograde fluorescent double-labeling study

The vestibular nuclear input into the flocculus and the uvula and nodulus of the caudal vermis was studied in rabbits by means of retrograde transport of the fluorescent tracers Fast Blue and Diamidino Yellow. Through simultaneous injection of the tracers in the homonymous lobules at either side of the midline, the distribution, the preference in laterality and the degree of collateralization of vestibulocerebellar neurons could be studied. The nucleus prepositus hypoglossi was included in the analysis. In the nucleus prepositus hypoglossi and in the medial vestibular nucleus 6% of the number of labeled neurons contained both tracers, against 4% in the descending vestibular nucleus. In the superior vestibular nucleus a statistically significant difference in the proportion of double-labeled neurons was found between cases with injections in the flocculus (1%) and the caudal vermis (9%). The relative distribution of single-labeled neurons projecting to either the flocculus or the caudal vermis was similar in most of the vestibular nuclei. A statistically significant preference for a projection to the flocculus in favor of one to the caudal vermis, was found for neurons in the medial vestibular nucleus and the prepositus hypoglossal nucleus. Statistically significant laterality preferences were found in the superior vestibular nucleus for the contralateral flocculus.

Neurons in raphe nuclei pontis and magnus have branching axons that project to medial preoptic area and cervical spinal cord. A fluorescent retrograde double labeling study in the rat

In this study, we utilized a double retrograde axonal tracing technique to investigate the possible existence of collateralized axonal projections from raphe nuclei ‘pontis’ and ‘magnus’ to both medial preoptic area (MPA) and cervical spinal cord (C 1-C 2). Following microinjections of fluorescent tracers Fast blue (FB) and Diamidino yellow (DY) within MPA and C 1-C 2, substantial numbers of FB and DY single-labeled neurons, as well as FB DY double-labeled neurons have been found within raphe nuclei ‘pontis’ and ‘magnus’.

Propriospinal neurons with ascending collaterals to the dorsal medulla, the thalamus and the tectum: a retrograde fluorescent double-labeling study of the cervical cord of the rat

Branching neurons with descending propriospinal collaterals and ascending collaterals to the dorsal medulla, the thalamus and the tectum were studied in the rat's cervical spinal cord (C1-C8), using the retrograde fluorescent double-labeling technique: Diamidino Yellow Dihydrochloride (DY) was injected in the cord at T2, True Blue (TB) was injected in the brain stem. DY-labeled descending propriospinal neurons were present in all laminae, except lamina IX. They were concentrated in lamina I, laminae IV to VIII, and in the lateral spinal nucleus, LSN. TB-labeled neurons projecting to the dorsal medulla were concentrated in lamina IV and the medial parts of laminae V and VI (probably representing postsynaptic dorsal column--PSDC--neurons), but were also present in lamina I, the LSN, the lateral dorsal horn, and in laminae VII and VIII. DY-TB double-labeled neurons giving rise to both a descending propriospinal collateral and an ascending collateral to the dorsal medulla were intermingled with the TB single-labeled neurons. About 4% of the descending propriospinal neurons gave rise to an ascending collateral to the dorsal column nuclei; these double-labeled cells constitute a sizable fraction (10%) of the PSDC neurons. TB-labeled spinothalamic and spinotectal neurons were located in lamina I, the lateral cervical nucleus (LCN), and LSN, the lateral lamina V, lamina VII and VIII, lamina X and in the spinal extensions of the dorsal column nuclei, predominantly contralateral to the TB injections. DY-TB double-labeled neurons were present throughout C1-C8 in the LSN, lateral lamina V, lamina VIII, ventromedial lamina VII, and lamina X. Only very few were observed in lamina I and the LCN, and none in the spinal extensions of the dorsal column nuclei. The double-labeled neurons constituted only a minor fraction of all labeled neurons; 3-5% of the spinothalamic neurons and about 1-7% of the spinotectal neurons were double-labeled. Conversely, only about 1% of the labeled descending propriospinal neurons gave rise to an ascending spinothalamic collateral, and even fewer (0.1 to 0.6%) to a collateral to the dorsal midbrain. The LSN displayed the highest relative content of branching neurons. Up to 20% of its ascending spinothalamic and spinotectal neurons and up to 8% of its descending propriospinal neurons were found to be branching neurons, indicating that the LSN constitutes an unique cell-group in the rat spinal cord.

Branching projections from subcoeruleus area neurons to medial preoptic area and cervical spinal cord revealed by double retrograde neuronal labeling

In this study we utilized a double retrograde axonal tracing technique to investigate the possible existence of collateralized axonal projections of subcoeruleus area neurons to both ‘medial preoptic area (MPA)’ and ‘cervical (C 1–C 3) spinal cord’. Following microinjections of fluorescent tracers (Fast blue (FB) and Diamidino yellow (DY)) within MPA and C 1–C 3, substantial numbers of FB and DY single-labeled neurons as well as FB-DY double-labeled branched neurons have been found within subcoeruleus area.

Non-motoneurons in the facial and motor trigeminal nuclei projecting to the cerebellar flocculus in the cat

The cerebellar projection from the facial and motor trigeminal nuclei was studied in the cat by means of retrograde axonal transport of wheat germ agglutinin-horseradish peroxidase and fluorescent tracers. The feline facial nucleus was cytoarchitectonically subdivided into ventromedial, ventrolateral, lateral, dorsal, intermediate and medial divisions (see Papez 1927), and the motor trigeminal nucleus into medial, ventral, intermediate, lateral and dorsal divisions. The neurons in the facial and motor trigeminal nuclei were classified as small (ovoid to round cells with a maximum diameter of the cell body of about 20 microns) or large (polygonal to round cells with maximum diameter of about 40 microns). After floccular injections of the wheat germ agglutinin-horseradish peroxidase complex, retrogradely labelled cells were found throughout the facial nucleus, but especially in its medial and dorsal divisions. In the motor trigeminal nucleus, labelled neurons were found only in the ventral, intermediate and lateral divisions. Cases with tracer deposition (implants or injections) in other parts of the cerebellar cortex or nuclei were all negative. All facial and motor trigeminal neurons labelled after floccular injections were smaller than the neurons labelled after injections in the facial mimic and masticatory muscles, and only single-labelled neurons were found following floccular injections of Fluoro-Gold and muscular injections of rhodamine-B-isothiocyanate in the same animals. These observations strongly suggest that the neurons in the facial and motor trigeminal nuclei which project to flocculus are of the non-motoneuron type.

Demonstration of axonal branching of fibres from certain precerebellar nuclei to the cerebellar cortex and nuclei: a retrograde fluorescent double-labelling study in the cat.

The projections from certain brain stem precerebellar nuclei to the cerebellar cortex and nuclei have been examined in the cat by using the retrograde fluorescent double-labelling technique. Crystalline Fluoro-Gold was implanted into the left cerebellar nuclei from the contralateral side and rhodamine-B-isothiocyanate was injected into the overlying cerebellar cortex. The inferior olive, the lateral reticular nucleus, and the reticular tegmental pontine nucleus all contained double- as well as single-labelled neurons, and it was concluded that these nuclei have a high number of neurons whose axons branch to both the cerebellar cortex and nuclei. The neurons in the paramedian reticular nucleus and the pontine nuclei proper appear to project only to the cerebellar cortex.