Trigeminal primary afferent neurons projecting directly to the solitary nucleus in the cat: A transganglionic and retrograde horseradish peroxidase study

After applying horseradish peroxidase to peripheral branches of the trigeminal nerve in the cat, the lingual and pterygopalatine nerves were found to contain fibers which ended ipsilaterally in the rostral portions of the solitary nucleus (SN); massively in the medial and ventrolateral SN, moderately in the intermediate and interstitial SN and sparsely in the ventral SN. The rostralmost part of the SN was free from labeled terminals. After injecting the enzyme into the SN portions rostral to the area postrema, small neurons were scattered in the maxillary and mandibular divisions of the trigeminal ganglion.     

Projections of extraocular muscle primary afferent neurons to the trigeminal sensory complex in the cat as studied with the transganglionic transport of horseradish peroxidase

The central projections of extraocular muscle primary afferent neurons were examined in the cat by means of transganglionic axonal transport of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). Injections of the extraocular muscle with WGA-HRP resulted in transganglionic terminal labeling within the ipsilateral trigeminal sensory complex. Although the density of trigeminal projections varied among cases, labeled axons and terminals were heavily and consistently found within the rostroventral portion of the pars oralis of the spinal trigeminal nucleus. The caudal part of the trigeminal principal sensory nucleus occasionally contained moderate labeling but very few deposits of HRP reaction product were noted in the pars interporalis and pars caudalis of the spinal trigeminal nucleus.     

The primary afferent projection of the greater petrosal nerve to the solitary complex in the rat, revealed by transganglionic transport of horseradish peroxidase

The primary afferent projection of the greater petrosal nerve (GPN) to the solitary complex was studied following application of horseradish peroxidase (HRP) to the GPN just distal to the geniculate ganglion. Labeled fibers were traced to the most rostral part of the solitary tract. Numerous collaterals entered the solitary complex from its dorsal and lateral aspects, and formed a dense plexus. They terminated in the dorsal half of the medial solitary nucleus at the level of the rostral half of the solitary complex, and in the ventrolateral and commissural nuclei at the level of the caudal half. The densest termination was observed in the medial solitary nucleus. Labeled terminals were found to contain round, clear synaptic vesicles and to make asymmetrical synaptic contacts with dendritic profiles.     

Efferent neurons to the labyrinth of Salamandra salamandra as revealed by retrograde transport of horseradish peroxidase

Application of horseradish peroxidase to the severed VIIIth nerve of Salamandra salamandra resulted in heavy bilateral labeling of neurons of the medullary reticular formation. These neurons closely resemble the Mauthner neuron in their widespread dendritic ramification. In most preparations axon collaterals are seen to leave the medulla via the contralateral VIIIth nerve. It is suggested that these neurons are labyrinthine efferents.     

Retinal projection to the nucleus of the optic tract in the cat as revealed by retrograde transport of horseradish peroxidase

Retrograde transport of horseradish peroxidase injected iontophoretically into the nucleus of the optic tract of cats revealed that the direction-selective cells in this pretectal nucleus receive direct retinal projections from small retinal ganglion cells, the so-called gamma-cells. These cells from a horizontal band on the contralateral retina. Few labeled cells are found in the ipsilateral temporal retina. The input from the contralateral retina is 10 times more numerous than from the ipsilateral one. In both retinae the highest concentration of labeled cells is near the area centralis.     

The facial nucleus of the rat: representation of facial muscles revealed by retrograde transport of horseradish peroxidase

The representation of facial muscle groups in the facial nucleus of rat was examined by retrograde transport of HRP. Motoneurons supplying muscle groups are arranged in longitudinal columns. Those supplying nasolabial muscles are located in the lateral and ventral intermediate segments, posterior auricular muscles in a medial column, platysma in an intermediate column; the lower lip and ocular muscles are in the ventral and dorsal segments respectively of the intermediate column. The posterior belly of the digastric muscle is supplied by motoneurons extending from the dorsal aspect of the facial nucleus to the caudal pole of the trigeminal motor nucleus.     

Morphometric study of glycine-immunoreactive neurons and terminals in the rat cuneate nucleus

The distribution of glycine-immunoreactive (glycine-IR) neurons and their associated axon terminals in the rat cuneate nucleus was studied using antiglycine postembedding immunoperoxidase labelling and immunogold staining, respectively. The immunoperoxidase-labelled glycine-IR neurons were widely distributed in the entire rostrocaudal extent of the nucleus. They made up 30.8% (9671/31368) of the neurons surveyed. Quantitative evaluation showed that the percentage of glycine-IR neurons in the caudal level was significantly higher than that in the middle and rostral levels. The glycine-IR neurons were small cells (mean area=198±1.9 μm², n=2862) with ovoid or spindle-shaped somata. Statistical analysis showed that the size of the glycine-IR neurons in the rostral level was significantly smaller than that in the middle and caudal levels. Immunogold labelled glycine-IR terminals which contained predominantly pleomorphic synaptic vesicles were mostly small (mean area=1.24±0.03 μm², n=286) and they constituted 24.7% (286/1158) of the total terminals surveyed. They formed axodendritic, axosomatic and axoaxonic synapses with unlabelled elements. It is suggested from this study that glycine is one of the major neurotransmitters involved in the depression of synaptic transmission in the cuneate nucleus.     

Laminar distribution and somatotopic organization of primary afferent fibers from hindlimb nerves in the dorsal horn. A study by transganglionic transport of horseradish peroxidase in the rat

Primary afferent nerve fibers to the spinal cord in the adult rat were labeled by applying horseradish peroxidase to the cut end of one of the following hindlimb nerves; the tibial, medial plantar, lateral plantar, common peroneal, saphenous, sural, lateral femoral cutaneous or obturator nerve. Maximal labeling intensity was found in the dorsal horn after 36-72 h survival. Labeling was observed in different dorsal horn laminae at different levels within the L1-S1 spinal cord segments, depending on which nerve horseradish peroxidase had been exposed to, probably reflecting the individual composition of afferent fiber types. Although a certain overlap was found, the central projections of the eight different nerves investigated formed well delineated three dimensional compartments within the medial 2/3 to 3/4 of the dorsal horn. This was most clearly discernible in lamina II. Although interindividual differences were present, bilaterally identical operations gave symmetrical projection patterns in the dorsal horn. The results indicate that dorsal horn projections of hindlimb nerves are organized in a highly ordered somatotopic fashion.     

Vestibular projections to the nucleus intercalatus of Staderini mapped by retrograde transport of horseradish peroxidase

Medullary afferent projections to the nucleus intercalatus of Staderini have been studied by retrograde transport of horseradish peroxidase (HRP) from highly localized injections. This nucleus receives afferent projections particularly from the medial and descending vestibular nuclei as well as from the nucleus praepositus hypoglossi of both sides. The nucleus intercalatus of Staderini represents therefore an area of integration for the vestibular systems of both sides.     

Segmental motor and sensory innervation of muscles in anterior leg compartment as revealed by retrograde transport of horseradish peroxidase

Horseradish peroxidase (HRP) tracing technique was used to label and localize motor and sensory neurons innervating tibialis anterior, extensor hallucis longus and extensor digitorum longus muscles of the anterior leg compartment of the rat. The tibialis anterior sensory neurons were located in the ipsilateral L4 and L5 spinal ganglia. Cells of origin of tibialis anterior motor endings were also found in the ipsilateral ventral horn of the same cord segments as the labeled sensory ganglia. Extensor hallucis longus sensory neurons were located in L4 to L6 spinal ganglia, while its labeled motor neurons were located in L4 and L5 spinal cord segments. The motor neurons innervating the extensor digitorum longus muscle were located in L4 to L6 spinal cord segments; its sensory neurons were previously localized. All labeled motor and sensory neurons were present on the ipsilateral side. Almost all motoneurons innervating the 3 muscles were present in the dorsolateral nucleus of the ventral horn.     

Postsynaptic dorsal column neurons in the cat: a study with retrograde transport of horseradish peroxidase

Summary In situ hybridization histochemistry and RNA blots were used to study the expression of glutamic acid decarboxylase (GAD) mRNA in rats with or without a unilateral lesion of midbrain dopamine neurons. Two populations of GAD mRNA positive neurons were found in the intact caudate-putamen, substantia nigra and fronto-parietal cortex. In caudate-putamen, only one out of ten of the GAD mRNA positive neurons expressed high levels, while in substantia nigra every second of the positive neurons expressed high levels of GAD mRNA. Relatively few, but intensively labelled neurons were found in the intact fronto-parietal cerebral cortex. In addition, one out of six of the GAD mRNA positive neurons in the fronto-parietal cortex showed a low labeling. On the ipsilateral side, the forebrain dopamine deafferentation induced an increase in the number of neurons expressing high levels of GAD mRNA in caudateputamen, and a decrease in fronto-parietal cortex. A smaller decrease was also seen in substantia nigra. However, the total number of GAD mRNA positive neurons were not significantly changed in any of these brain regions. The changes in the levels of GAD mRNA after the dopamine lesion were confirmed by RNA blot analysis. Hence, midbrain dopamine neurons appear to control neuronal expression of GAD mRNA by a tonic down-regulation in a fraction of GAD mRNA positive neurons in caudate-putamen, and a tonic up-regulation in a fraction of GAD mRNA positive neurons in fronto-parietal cortex and substantia nigra.     

The cerebellar projection from the lateral reticular nucleus as studied with retrograde transport of horseradish peroxidase

Summary The cerebellar projection from the lateral reticular nucleus (NRL) was studied in cats by means of retrograde axonal transport of horseradish peroxidase (the projection to the paramedian lobule was not included, see Brodal, 1975, for afferents to this cortical region). The entire cerebellar cortex and all cerebellar nuclei receive fibres from the NRL. The strongest connection is with the anterior lobe and lobulus VIIIB of the posterior lobe vermis. As concerns the anterior lobe the observations confirm the previous finding by Brodal (1975) that there is a clearcut topical pattern in the nuclear projection to this part of the cerebellum. The observations furthermore show that crus II is the only cerebellar region devoid of fibres from the subtrigeminal part of the NRL.The cerebellar projection from the NRL is bilateral with a heavy ipsilateral preponderance. The large majority of the labeled cells within the NRL are of the small category (<25 m in size). This and the other findings are discussed in relation to previous studies on the efferent and afferent connections of the nucleus.     

Cerebellar afferent projections from the perihypoglossal nuclei: An experimental study with the method of retrograde axonal transport of horseradish peroxidase

Summary Details of cerebellar afferent projections from the perihypoglossal nuclei were studied in the cat by means of retrograde axonal transport of horseradish peroxidase (HRP). Labeled cells were observed bilaterally (with a preponderance ipsilaterally) in nuclei intercalatus and praepositus hypoglossi following injections in various folia of the entire vermis, paraflocculus, flocculus, fastigial nucleus, and the nucleus interpositus anterior and posterior. Relatively high densities of labeled cells were found in nucleus intercalatus following injections in the anterior part of the vermis, whereas labeled cells in nucleus praepositus hypoglossi were found more frequently following injections in the posterior part of the vermis. Labeled cells in the nucleus of Roller were found only following injections in the anterior lobe vermis, posterior vermal lobules VI and VII, in the flocculus and in the nucleus interpositus anterior. No labeled cells could be detected in the three subdivisions of the perihypoglossal nuclei following HRP injections in crus I, crus II, paramedian lobule, and lateral cerebellar nucleus. The distribution of the HRP positive cells indicated the presence of a topographically organized projection from certain regions of the perihypoglossal nuclei to different parts of the cerebellum. The afferent and efferent connections of the perihypoglossal nuclei in relation to a functional role in eye and head movements are discussed.Abbreviations in Figures a,b,c sublobules of lobules V, VI and VII - f.apm. ansoparamedian fissure - f.icul. intraculminate fissure - f.in.cr. intercrural fissure - f.pc. preculminate fissure - f.pfl. parafloccular fissure - f.p.l. posterolateral fissure - f.ppd. prepyramidal fissure - f.pr. fissura prima - f.prc. precentral fissure - f.prc.a. precentral fissure a - f.p.s. posterior superior fissure - f.sec. fissura secunda - fl. flocculus - g.n. VII genu of facial nerve - HII-HVI, HIX hemispheral lobules II–VI, IX - HVIIA cr.Ia,p; cr.IIa,p anterior and posterior folia of crus I and II of the ansiform lobule - HVIIB, HVIIIA,B sublobules A and B of hemispheral lobules VII and VIII - ic nucleus intercalatus - l.ans. ansiform lobule - N.f. nucleus fastigii - Nfc nucleus cuneatus - Nfg nucleus gracilis - N.i.a. nucleus interpositus anterior - N.i.p. nucleus interpositus posterior - N.l. nucleus lateralis - pfl.d. dorsal paraflocculus - pfl.v. ventral paraflocculus - Ph nucleus praepositus hypoglossi - Ro nucleus of Roller - S solitary tract - s.int.cr.1,2 intracrural sulcus 1 and 2 - SL lateral nucleus of the solitary tract - SM medial nucleus of the solitary tract - VIN inferior vestibular nucleus - VLD lateral vestibular nucleus, dorsal division - VMN medial vestibular nucleus - I-VI vermian lobules I–VI - VI nucleus of abducent nerve - VIIA,B; VIIIA,B anterior and posterior sublobules of lobules VII and VIII - IX uvula - X dorsal motor nucleus of vagus nerve; nodulus - XII nucleus of hypoglossal nerve Parts of this paper were presented at the Symposium Control of Gaze by Brain Stem Neurons, Paris, July 13–15, 1977On leave from the Laboratory of Neurobiology, Faculty of Science, Mahidol University, Bangkok, Thailand, under NORAD Fellowship Program from the Norwegian Agency for International Development     

Ultrastructure of visual callosal neurons in cat identified by retrograde axonal transport of horseradish peroxidase

Summary The ultrastructure of neurons at the border of areas 17 and 18 of the visual cortex of the cat was studied by the combined use of the retrograde transport of horseradish peroxidase (HRP) and electron microscopy. Callosal neurons were retrogradely labelled by injecting HRP at the 17/18 border region of the contralateral hemisphere. They were found mainly in layer III but also in IV and VI. They were most commonly pyramidal cells and less often large, spiny stellate cells. Pyramidal callosal neurons received only symmetrical synapses on their soma and mainly symmetrical (but a few asymmetrical) synapses on their dendritic shafts. Their abundant spines received asymmetrical synapses. The stellate cells were contacted by moderate numbers of symmetrical and asymmetrical axodendritic and axosomatic synapses and also had asymmetrical axospinous contacts. We propose that the callosal stellate neurons consist of a class of large spiny stellates, recognizable by light and electron microscopic criteria.The work described in this paper forms part of a study for a doctoral dissertation in the University of Lausanne by J. P. Hornung.     

Various types of corticotectal neurons of cats as demonstrated by means of retrograde axonal transport of horseradish peroxidase

Summary The retrograde labeling of cortical neurons with horseradish peroxidase (HRP) was used to investigate the morphological features of neurons in various cortical areas projecting to the superior colliculus in the cat.Corticotectal cells were found to be labeled in layer V of the entire cerebral cortex. The number of labeled cells and their locations varied according to the sites of injections of HRP in the colliculus. Most of the Corticotectal cells identified in the present study were small (9–20 m in diameter, 66%) and medium (20–40 urn, 30%) pyramidal neurons and only 4% of them were large (more than 40 m). The labeled cells, 261 in total number, had somal diameters of 20.8±8.0 m (mean and SD). The range of sizes of the labeled neurons was different in different cortical areas. For example, the labeled neurons in the Clare-Bishop area had a greater proportion of large diameter cells than in other areas.The present findings are largely in agreement with the previous data of anterograde degeneration methods with respect to the topographical correlation of the Corticotectal projections. However, in some cortical areas, e.g., the sensorimotor and the first visual (area 17) cortex of the lateral surface of the hemisphere, relatively small numbers of Corticotectal neurons appear to have been labeled by retrogradely transported HRP. The sparsity of the labeled neurons in certain cortical areas may reflect the existence of Corticotectal neurons with axon collaterals supplying brain structures other than the superior colliculus.Abbreviations A.c. Aqueductus cerebri - AEct Gyrus ectosylvius anterior - AEs Sulcus ectosylvius anterior - AI Stratum album intermediale - AL Gyrus lateralis anterior - AP Stratum album profundum - AS Gyrus sylvius anterior - Cd Nucleus caudatus - F.l.m. Fasciculus longitudinalis medialis - GI Stratum griseum intermediale - GP Stratum griseum profundum - GS Stratum griseum superficiale - Ic Inferior colliculus - L Left - MEct Gyrus ectosylvius medius - MS Gyrus sylvius medius - MSup Gyrus suprasylvius medius - N.r. Nucleus ruber - O Stratum opticum - P Pontine nuclei - P.c. Pedunculus cerebri - PEct Gyrus ectosylvius posterior - P.g. Periaqueductal gray matter - PSigm Gyrus sigmoideus posterior - PSup Gyrus suprasylvius posterior - R Right - Sc Superior colliculus - S.n. Substantia nigra - Z Statum zonale - II Optic nerve - III and IV Motor nuclei of cranial nerves     

Cerebellar afferents from the paramedian reticular nucleus studied with retrograde transport of horseradish peroxidase

Summary Details in the cerebellar projections from the paramedian reticular nucleus (PRN) were studied in cats and monkeys by means of retrograde axonal transport of horseradish peroxidase (HRP). In the cat the majority of the fibres projects to the anterior lobe and to the vermis of the posterior lobe (with the exception of lobules VIIB and VIIIA). A less conspicuous projection was found to the lobulus simplex, the crura and the flocculus. The cerebellar nuclei, the paramedian lobule and the paraflocculus appear to be weakly connected with the PRN. A similar distribution of the cerebellar afferent fibres was found in the monkey material. The three subgroups of the PRN in the cat are not equal in their projection. The dorsal group appears to be connected with the greater part of the cerebellar cortex and with all nuclei. The ventral group lacks a connection with lobulus IX, the flocculus and the paraflocculus, and the accessory group appears to have its strongest connection with lobulus I (lingula), the flocculus and the vermal lobules VII–X. The findings are discussed in relation to other studies on the efferent and afferent connections of the nucleus.On leave from the Laboratory of Neurobiology and Department of Anatomy, Faculty of Science, Mahidol University, Bankok, Thailand, under the Fellowship Program of the Norwegian Agency for International Development (NORAD)     

Projections to gyrus sigmoideus from the substantia nigra in the cat,as revealed by the horseradish peroxidase retrograde transport technique

After injections of horseradish peroxidase in the gyrus sigmoideus of the cat frontal cortex, labelled neurones were found in the substantia nigra and the ventral tegmental area of Tsai. Neurones distributed bilaterally clearly predominated in the side of the injection in the rostral sections, but differences in number were less at caudal levels. The present findings confirm the existence of a direct mesencephalocortical projection from this ventral tegmental region, and provide a morphological substrate for a better understanding of the role of the dopaminergic systems in the motor cortical regulation.     

Morphology of migrating trigeminal motor neuroblasts as revealed by horseradish peroxidase retrograde labeling techniques

The trigeminal motor sensory roots were severed in chick embryos on days 2.5 4.5 of incubation and horseradish peroxidase applied to the wound. This procedure retrogradely labels developing trigeminal motor neuroblasts whose axons are at the level of the incision. In day 2.5 embryos, migrating and lateral trigeminal motor neuroblasts were labeled only when the incision was 8 μm from the metencephalon. Migrating cells did not have somatic processes whereas cells of the lateral nucleus had one dendritc-like process extending dorsally. No cells of the medial column, a cluster of premigratory trigeminal motor neuroblasts, were labeled at this age.In the 3-, 3.5-, 4- and 4.5-day embryos, medial column cells, migratory cells and lateral nucleus cells were retrogradely labeled by this procedure. At all these ages, medial column cells tend to have few somatic filopodia migratory cells tend to have increased filopodia as they proceed laterally, and lateral nucleus cells arc characterized either by a single, long dendrite-like process dorsally directed, or a radiation of short, stubby processes. Axons of medial column and migratory cells take a sinuous course across the metencephalon and frequently exhibit small branches and localized swellings. Axons of lateral nucleus cells rarely have branches within the brain stem and usually enter the motor root at an acute angle from their origin at the soma.The central processes of the trigeminal ganglion cells are also labeled with this procedure. In all embryos these fibers were confined to the trigeminal spinal tract at the level of the trigeminal motor nucleus. Caudally, small fibers were observed to exit this tract in the presumed region of the developing trigeminal spinal nucleus.This study demonstrates that axonal outgrowth into the periphery precedes somatic migration and translocation in the trigeminal motor nucleus During their migration, trigeminal motor neuroblasts appear to be in proximity to axons of adjacent migrating cells. Considerable differentiation occurs during this process.     

The afferent connections of the inferior olivary complex in rats: A study using the retrograde transport of horseradish peroxidase

Retrograde transport of horseradish peroxidase (HRP) was used to define the origin of afferents to the inferior olivary complex (IOC) in rats. Using both ventral and dorsal surgical approaches to the brainstem, HRP was injected into the IOC through a micropipette affixed to the tip of a 1-μl Hamilton syringe. After a 2-day postoperative survival, animals were sacrificed by transcardiac perfusion with a 1% paraformaldehyde-1.25% gluteraldehyde solution, and brains were processed according to the DeOlmos protocol (1977), using o-dianisidine as the chromogen. Labeled cells were found at many levels of the nervous system extending from lumbar spinal cord to cerebral cortex. This wide-ranging input from numerous regions clearly underscores the complexity of the IOC and its apparent involvement in several functions. Within the spinal cord, labeled neurons were identified from cervical to lumbar but not at sacral levels. These neurons were found contralaterally in the neck region of the dorsal horn and in the medial portions of the intermediate gray. In the caudal brainstem, reactive cells in the dorsal column nuclei, the spinal trigeminal nucleus, and the subnucleus y of the vestibular complex were observed primarily contralateral to the injection sites. Labeling within the gigantocellular, magnocellular, ventral, and lateral reticular nuclei and the nucleus prepositus hypoglossi was primarily ipsilateral. Reactive neurons in the medial and inferior vestibular nuclei were predominantly ipsilateral or contralateral to HRP injections into the caudal or rostral IOC, respectively. The dentate and interposed nuclei of the cerebellum contained small, lightly labeled neurons primarily contralateral to the injection site, while the fastigial nuclei contained a few relatively large, heavily labeled cells bilateral to caudal olivary injections. Ipsilaterally labeled mesencephalic regions included the periaqueductal gray, interstitial nucleus of Cajal, rostromedial red nucleus, ventral tegmental area, medial terminal nucleus of the accessory optic tract, nucleus of the optic tract, and the lateral deep mesencephalic nucleus. The caudal part of the pretectum and small cells of the stratum profundum of the superior colliculus were labeled predominantly contralateral to the injection. In the caudal diencephalon labeled neurons were most numerous within the nucleus of Darkschewitsch and the subparafascicular nucleus, primarily ipsilateral to olivary injections. Scattered reactive neurons were also found within the ipsilateral zone incerta. With the exception of the zona incerta, all labeled mesencephalic and diencephalic nuclei had some bilateral representation of labeled cells. No labeled neurons were identified within the basal ganglia, while numerous reactive cells were found bilaterally within layer V of the frontal and parietal cerebral cortex.