bluuebunny/crossref_metadata_2025 huggingface dataset:
Afferent projections to the oral motor nuclei in the rat
Authors: Travers Joseph B. , Norgren Ralph
Published: May 2005

Projections to the trigeminal, facial, ambiguus, and hypoglossal motor nuclei were determined by using horseradish peroxidase histochemistry. Most of the afferent projections to these motor nuclei were from the brain‐stem reticular formation, frequently in areas adjacent to other synergetic motor nuclei. The reticular formation lateral to the hypoglossal nucleus and reticular structures surrounding the trigeminal motor nucleus projected to each of these other brainstem motor nuclei involved in oral‐facial function. Afferent projections to these motor nuclei also were organized along the ros‐trocaudal axis. Within the reticular formation most of the afferent projections to the trigeminal motor nucleus originated rostral to the majority of neurons projecting to the hypoglossal and ambiguus nuclei, which in turn were rostral to the primary source of reticular afferents to the facial nucleus. In comparison, projections from the sensory trigeminal nuclei and nucleus of the solitary tract were sparse. The interneuron pools that project to the orofacial motoneurons provide one further link in understanding the brain‐stem substrates for integrating oral and ingestive behaviors.
Anatomy of the gustatory system in the hamster: Central projections of the chorda tympani and the lingual neirve
Authors: Whitehead Mark C. , Frank Marion E.
Published: May 2005

The sensory modalities of taste and touch, for the anterior tongue, are relegated to separate cranial nerves. The lingual branch of the trigeminal nerve mediates touch; the chorda tympani branch of the facial nerve mediates taste. The chorda tympani also contains efferent axons which originate in the superior salivatory nucleus. The central projections of these two nerves have been visualized in the hamster by anterograde labelling with horseradish peroxidase (HRP).

Afferent fibers of the chorda tympani distribute to all rostral‐caudal levels of the solitary nucleus. They synapse heavily in the dorsal half of the nucleus at its rostral extreme; synaptic endings are sparser, and located lat‐erally in caudal region. These taste afferents trave caudally in the solitary tract and reach different levels by a series of collateral branches which extend medially into the solitary nucleus, where they exhibit preterminal and terminal swellings. Taste atferentaxons range in diameter from 0.2 μm to 1.5 μm. The thickest axons project exclusively to the rostral and intermediate subdivisions of the solitary nucleus; the fine ones may distribute predominantly to the caudal subdivision.

Afferent fibers of the lingual nerve terminate heavily in the dorsal one‐third of the spinal nucleus of the trigeminal nerve and also as a dense patch in the lateral solitary nucleus at the midpoint between its rostral and caudal poles. This latter projection overlaps that of the chorda tympani. Thus the two sensory nerves which subserve taste and touch from coincident peripheral fields on the tongue converge centrally on the intermediate subdivision of the solitary nucleus.

Efferent neurons of the superior salivatory nucleus were labelled retro‐gradely following application of HRP to the chorda tympani. These cells are located ipsilaterally in the medullary reticular formation ventral to the rostral pole of the solitary nucleus; their dendrites are oriented dorsoventrally. The efferent axons course dorsally, form a genu lateral to the facial somato‐motor genu, and course ventrolaterally through the spinal nucleus of the trigeminal nerve to exit the brain ventral to the entering facial afferents.
Spinal neurons reaching the lateral reticular nucleus as studied in the rat by retrograde transport of horseradish peroxidase
Authors: Menétrey D. , Roudier F. , Besson J. M.
Published: May 2005

An anatomical technique based on the retrograde transport of horseradish peroxidase (HRP) was used to investigate the projections of spinal cord neurons to the lateral reticular nucleus (LRN). Labeled cells were found at all spinal levels and in particular large numbers in cervical and lumbar segments. Various spinal areas gave rise to cells of origin of this tract, which appears to be more prominent than any other tract previously studied with a similarapproach.

Labeling common to all spinal segments was observed in (1) ventro‐medial parts of both intermodiate zone and ventral horn (laminae VII, V and X), mainy contralalerally; (2) the reticular extension of the neck of the dorsal horn partly bilateral; and (3) superficial layers of the dorsal horn and nucleus ofthe dorsolaleral funiculus (NDLF), mainly contralateral and projecting essentially to the lateral zone of the LRN.

Additional labeling was observed at cervical and lumbar levels, each with specific qualities: (1) the cervical enlargement, which displayed labeling in the central part of the ipsilateral intermediate zone (lamina VII): (2) the rostral lumbar levels, which had projections from the contralateral median portion of the neck of the dorsal horn. These latter projections appear to be specific to pathways reaching the lateral reticular nucleus and the inferior olive.

Control injections in neighboring structures demonstrated the similarity between the afferents to the lateral reticular nucleus and the inferior olive (except lamina I and NDLF projections) and the differences between these afferents and those projecting to the dorsal reticular formation, i.e., the nucleus reticularis ventralis.
The fine structure of the rat subthalamic nucleus: An electron microscopic study
Authors: Chang H. T. , Kita H. , Kitai S. T.
Published: May 2005

The normal ultrastructure of the rat subthalamic nucleus (STH) was studied. The STH consisted of tightly packed neurons distributed within a neuropil filled with large numbers of blood vessels and thinly myelinated fibers. The somata of STH neurons (diameters, D, between 10 and 25 μm) contained abundant organelles but had only a small amount of both smooth and rough endoplasmic reticulum. The nuclei had deeply invaginated nuclear envelopes and pale nucleoplasm with little heterochromatin. STH neurons often were tightly apposed without any intervening glial membranes. Similar appositions were also found between somata and dendrites, dendrites and dendrites, and dendrites and initial axon segments. Although puncta adhaerentia were often observed, no gap junctions were found on any of these membrane appositions.

In the neuropil, the dendrites were mostly smooth and thin (D between 0.5 and 1 μm) with an occasional stubby spine or thin dendritic appendage. At least two types of axon terminals were identified. Type 1 terminals (D up to 1 μm) contained medium‐sized round vesicles (D about 45 nm) and formed asymmetrical synapses. Type 2 terminals were often large (D up to 5 μm) and contained both round and slightly flattened vesicles (D up to 50 nm). The type 2 terminals frequently formed adherens junctions with their postsynaptic targets in addition to forming relatively symmetrical synaptic junctions. The remaining axon terminals included a small number of terminals with various morphological characteristics and possibly some tangentially sectioned type 1 and type 2 terminals. Therefore they have not been classified as individual types in this study. A quantitative analysis indicated that the type 1 terminals formed synapses mainly with thin dendrites whereas the type 2 terminals formed synapses mainly with somata and larger dendrites.
Central projections of vestibular afferents from the horizontal semicircular canal in the carpet shark Cephaloscyllium isabella
Authors: Housley Gary D. , Montgomery John C.
Published: May 2005

This study utilizes anterograde axonal transport of cobaltous‐lysine and conventional silver‐staining techniques to study the central projections of the horizontal semicircular canal branch of the VIII nerve within the vestibular nuclei of the carpet shark Cephaloscyllium isabella. Two major terminating axon fields were observed, one caudal and one rostral to the entrance of the VIII nerve, corresponding to the ventral vestibular nucleus and superior vestibular nucleus, respectively. Both fields appear to be located within the ventral portion of the nuclei indicating an apparent subdivision of the VIII nerve projections within the brainstem. The resolution of the sensitive cobalt tracer indicates the presence of both dendritic and pericellular termination of these primary afferent fibres. In the area immediately caudal to the entrance of the VIII nerve a number of labelled primary afferent fibres project to the ventral region of the intermediate nucleus. Other fibres follow the visceral sensory root VII and terminate proximal to the sulcus limitans of His within the dendritic field of the neurons of the nucleus magnocellularis. Some fibres turn ventromedially from the main group of the ascending fibres and terminate in the area of the inferior reticular formation.
An analysis of the time of origin of neurons in the entorhinal and subicular cortices of the cat
Authors: Wyss J. M. , Sripanidkulchai B. , Hickey T. L.
Published: May 2005

The [3H]thymidine autoradiographic method was used to determine the birth dates of neurons in the cat parahippocampal gyrus. Cat fetuses were exposed to a single pulse of the radioactive marker between the 20th and 55th embryonic days. All animals were delivered normally and allowed to survive for 2–6 months postnatal. The resulting autoradiographs demonstrate three spatiotemporal gradients of cell birth in the entorhinal and subicular cortices. First, an inside‐out gradient is apparent; i.e., neurons in the deeper layers are born earlier than those in the more superficial layers. Second, a rhino to dentate gradient exists. Accordingly, cells closer to the lateral entorhinal region tend to be generated earlier than those further away. Third, a temporal to septal gradient is present. Neurons close to the anterior pole of the temporal lobe are born earlier than those more caudally located. Whereas the first two gradients have been observed in other species, the latter gradient has not been reported consistently. Three exceptions to these overall gradients exist. First, neurons near the layer I/II border are born earlier than the majority of the layer II neurons. Second, neurons near the transition zone between two adjacent regions are born earlier than neurons located in the middle of each region. Third, the prosubiculum and subiculum do not exhibit a clear inside‐out or temporal to septal gradient.
Differential olivocochlear projections from lateral versus medial zones of the superior olivary complex
Authors: Guinan John J. , Warr W. Bruce , Norris Barbara E.
Published: May 2005

An anterograde tracer (35S‐methionine) was injected unilaterally in the superior olivary complex (SOC) at regions previously demonstrated by retrograde labeling to contain olivocochlear (OC) cell bodies. Quantitative analysis of cochlear autoradiographs from these cats demonstrates that there are two OC systems. The lateral OC system has cell bodies lateral to the medial superior olivary nucleus (MSO) and projects to the inner hair cell (IHC) region bilaterally (mostly ipsilaterally). The medial OC system has cell bodies medial, ventral, and anterior to the MSO and projects to the outer hair cell (OHC) region bilaterally (mostly contralaterally). A single medial OC neuron innervates many small patches of OHCs with substantial gaps between the patches. Medial OC neurons also appear to project to the IHC region to a small extent. A review of the literature with the medial‐lateral division of OC efferents in mind reveals many differences between these two systems. In particular, lateral OC axons are unmyelinated and innervate the dendrites of radial afferent fibers under IHCs, whereas medial OC axons are myelinated and directly innervate OHCs. Although both systems appear to be cholinergic, the lateral OC system also shows met‐enkephalin‐like immunoreactivity. The synapses of the medial OC system are formed in development before those of the lateral OC system and they degenerate more slowly after the OC axons are cut. The many differences between these two OC systems suggest that they are functionally separate systems.
An HRP study of the central course of sensory intermediate and vagal fibers in peripheral facial nerve branches in the cat
Authors: Arvidsson Jan , Thomander Lars
Published: May 2005

Previous studies have shown that sensory fibers of intermediate and vagal nerve origin are present in facial nerve branches to the mimetic muscles in the cat. In the present study the central course of these fibers has been examined by transganglionic transport of horseradish peroxidase (HRP). In some of these experiments the facial nerve proper was transected central to the site of HRP application. In this way, the central course of the vagal fibers could be studied separately. For comparison HRP‐conjugated wheat germ agglutinin was injected into the geniculate ganglion, revealing the central course of the entire afferent component of the intermediate nerve. The results show that labeled sensory intermediate nerve fibers, at their level of entrance in the brainstem, form a tract at the dorsal margin of the spinal trigeminal tract (5T). While some fibers ascend from this level to terminate in the main sensory trigeminal nucleus, and a few fibers terminate in the rostral part of the solitary tract nucleus, the majority take a descending course. The main site of termination for these descending fibers is in the medial part of the C2 dorsal horn. Terminal labeling is also seen in the ventrolateral part of the cuneate nucleus (CUN) and in a small area of gray substance between CUN and trigeminal nucleus caudalis. After entering the brainstem some sensory vagal fibers project to the trigeminal nucleus interpolaris and to an interstitial nucleus within the 5T, but the larger part joins the descending tract of intermediate nerve fibers. These descending vagal fibers have a terminal distribution pattern similar to the intermediate nerve fibers.
Trigeminal projections to supratentorial pial and dural blood vessels in cats demonstrated by horseradish peroxidase histochemistry
Authors: Mayberg Marc R. , Zervas Nicholas T. , Moskowitz Michael A.
Published: May 2005

Anatomical and clinical observations suggest that supratentorial vascular structures contain afferent projections from the trigeminal ganglia. To characterize this innervation, horseradish peroxidase (HRP) and HRP conjugated to wheat germ agglutinin were applied to the pial and dural arteries and sinuses of 33 cats. HRP was restricted to the site of interest by applying it dissolved in a viscous polymer, polyvinyl alcohol (PVA), to achieve slow release and minimize diffusion. The ganglia of cranial nerves V, VII, IX, and X and the superior cervical ganglia (SCGs) were examined bilaterally for the presence of retrogradely transported protein. Horseradish peroxidase applied to the proximal middle cerebral artery was located in cell bodies occupying the portion of the ipsilateral trigeminal ganglion corresponding to the ophthalmic division and throughout both SCGs. When the tracer was applied to the right anterior or posterior superior sagittal sinus, HRP‐positive cells were present as above, predominantly in the ipsilateral trigeminal ganglia corresponding to the opthalmic division and throughout both SCG. When applied to the right middle meningeal artery, HRP was observed within neurons of ipsilateral SCG and in the ophthalmic division of trigeminal ganglia; a few enzyme‐containing cells were present in ipsilateral regions corresponding to the second and third divisions. These observations support the concept that supratentorial vascular structures receive afferent nervous projections from trigeminal neurons.
The development of axonal connections in the central olfactory system of rats
Authors: Schwob James E. , Price Joseph L.
Published: May 2005

The development of the cytoarchitecture and axonal connections of the central olfactory system were studied in fetal and neonatal rats from E16. In contrast to neocortical development, the olfactory cortex lacks a distinct cortical plate. In the piriform cortex and the olfactory tubercle the cellular laminae emerge simultaneously, while in the anterior olfactory nucleus, there are morphogenetic gradients from superficial to deep as well as from caudal to rostral which parallel the known cytogenetic gradients. Parallel morphogenetic and cytogenetic gradients are also present in the lateral to medial axis of the olfactory tubercle.

The projection from the olfactory bulb and the associational projections from the piriform cortex begin to develop well before birth. At E17 fibers from the bulb are limited to the lateral olfactory tract (LOT) and the molecular layer just deep to it, and then spread out caudally, laterally, and medially away from the LOT. This sequence of innervation parallels and predicts the density of innervation in the adult: those areas which are innervated first (such as the piriform cortex deep to the LOT) ultimately receive the heaviest innervation; conversely, those areas which are innervated very late (such as the medial olfactory tubercle) receive the lightest projection.

The intracortical projections from the anterior and posterior piriform cortex extend into layer I ipsilaterally by E20 and obtain their adult distribution by the middle of the first postnatal week. On the other hand, fibers from the anterior olfactory nucleus and the entorhinal area do not reach their full adult extent until the second postnatal week. Similarly, the crossed projection of the anterior piriform cortex to the contralateral posterior piriform cortex does not grow into layer I until this later time. The timing of fiber ingrowth showed no relation to the trajectory or eventual areal or laminar termination of fibers. As with the olfactory bulb projection, the timing may influence the density of termination.

Centrifugal fibers to the bulb are demonstrable around the time of birth both by the retrograde transport of horseradish peroxidase (HRP) and by the anterograde transport of 3H‐leucine. The arrival of additional fibers during the remainder of the first postnatal week parallels the known cytogenetic and morphogenetic gradients in the areas in which they arise.

The projections of the olfactory cortex to the lateral hypothalamic area and the mediodorsal thalamic nucleus are evident before birth. This correlates with the early generation of the cells which give rise to these projections.
The development of lamination of afferent fibers to the olfactory cortex in rats, with additional observations in the adult
Authors: Schwob James E. , Price Joseph L.
Published: May 2005

The complementary distribution of the fibers from the olfactory bulb and the intracortical associational fibers to layers Ia and Ib, respectively, of the olfactory cortex has been examined in both adult and neonatal rats, using horseradish peroxidase (HRP) and 3H‐leucine as double tracers in the same animal. The observations presented here confirm and extend the previous demonstration (Price, '73) that in the adult the two projections are essentially nonoverlapping throughout the olfactory cortex. Indeed, when the distribution of axons from the olfactory bulb (labeled by HRP inserted into a cut in the LOT) is compared on the same section with that of associational fibers (labeled by 3H‐leucine injected into the cortex), the overlap between the two projections is limited to a zone only 5–10 μm in width in both the piriform cortex and olfactory tubercle.

In contrast, at P1 the two projections overlap throughout layer I, although the bulbar and associational fibers are slightly concentrated superficially and deeply in layer I, respectively. This overlap is especially prominent in the part of the anterior piriform cortex deep to the LOT. During the remainder of the first postnatal week, this overlap resolves and by P7 the segregation of the two sets of afferent fibers is nearly equivalent to that seen in the adult.

However, there are several instances in adults where the segregation of these afferents does not develop. First, a relatively small population of aberrant axons derived from the LOT may be traced from layer Ia into layer Ib and then back to layer Ia. Most of these axons are large in diameter and lack the boutonlike varicosities found on smaller axons in layer Ia. They are most prominent in areas where the cortex is highly curved. Second, in layer I of the nucleus of the lateral olfactory tract, bulbar and associational fibers are extensively intermingled. In this case also, the bulbar fibers are large in diameter with only a few boutonlike varicosities.

The developmental emergence of afferent segregation and its breakdown in cases where the fibers from the olfactory bulb do not form boutons suggest that an interaction between the two distinct sets of fibers and the dendritic field is responsible for the normal development of this segregation and that this interaction depends on the process of synaptogenesis.
The development of physiological responses of the piriform cortex in rats to stimulation of the lateral olfactory tract
Authors: Schwob James E. , Haberly Lewis B. , Price Joseph L.
Published: May 2005

Extracellular recording techniques in rats were used to follow the postnatal development of the evoked response of the piriform cortex to electrical stimulation of the lateral olfactory tract (LOT) from birth to adulthood. As in other species, LOT shock in adult rats produces short‐latency activation of units in piriform cortex and an extracellular field potential consisting of three components: a surface‐negative component, the A1 wave (corresponding to the cortical monosynaptic EPSP evoked by the LOT fibers); a second surface‐negative component, the B1 wave (corresponding to reactivation of layer I dendrites by intracortical fibers); and a late surface‐positive component, the period 2 wave. A conditioning shock 20–150 msec before the test shock profoundly inhibits both evoked unit activity and the B1 wave, while it facilitates the A1.

At birth, units can be orthodromically activated by LOT stimulation in association with the A1 wave. There is also a surface‐positive spikelike wave, the S wave, which represents the summation of cortical unit activity. The B1 wave is apparent early in the first postnatal week. However, in contrast to the prominent inhibition in the adults, for the first few days after birth, single‐unit responses, multiple‐unit activity, and the S wave are all facilitated by a preceding conditioning shock with intervals of 200 msec or less, in association with the facilitation of the A1 wave. A shift to inhibition is apparent with longer intershock intervals of 300–700 msec, which exceed the period during which paired shocks facilitate the A1 wave. During the remainder of the first two postnatal weeks, partial suppression of evoked activity with intervals of less than 200 msec appears and progressively increases in strength, but inhibition at very long intershock intervals remains greater in magnitude. During this time, the duration of the inhibitory period also decreases to near the adult value of 200–300 msec. In the third postnatal week the pattern was similar to that in the adult, but the inhibition was still clearly weaker than in adults. These results suggest a delayed maturation of the cortical inhibitory circuitry; this conclusion has also been suggested by previously published observations in the developing neocortex and hippocampus.

In addition, the acceleration with age of the conduction velocity of axons in the LOT was analyzed. The adult value of 9.6 m/sec was not achieved until some time after postnatal day 15, which parallels the myelinization of the tract as observed with the light microscope.
Golgi‐like immunoperoxidase staining of dopamine neurons in the reticular formation of the rat brainstem using antibody to tyrosine‐hydroxylase
Authors: Köhler Christer , Goldstein Menek
Published: May 2005

The distribution and morphology of presumed dopaminergic neurons within the reticular formation (RF) and the ventrolateral tegmental area (VLT) were studied by using a specific antibody to the enzyme that converts tyrosine to dihydroxyphenylalanine, tyrosine‐hydroxylase (TH), in combination with a sensitive immunoperoxidase method (Hsu et al., '81). Incubation of thick (70–120 μm) sections for 3–5 days in high dilutions of antibody resulted in staining of TH‐immunoreactive neurons in a Golgi‐like fashion. Analysis of serial sections cut in the coronal, horizontal, and parasagittal planes revealed an extensive system of TH‐positive neurons in the RF and VLT extending from the Edinger‐Westphal nucleus caudally to the level of the decussations of the superior cerebellar peduncle. Within this region, the TH‐positive cells belong to two subgroups: (1) a relatively well‐defined population of cells aggregated in the reticular formation (corresponding to cell group A8 of Dahlström and Fuxe, '64), and (2) a more loosely defined group of cells that appears to be continuous with the cells of the nucleus raphe linearis. This latter cell group extends laterally from the midline to the nucleus parapeduncularis.

An analysis of the individual TH‐immunoreactive cells revealed large differences in their morphology. Thus, the somata of TH‐positive cells in the RF and the VLT are fusiform, ovoid, or triangular. A majority of the TH neurons are of medium (long axis: 15–35 μm) to large (long axis: 35–40 μm) size. While the cells in the A8 area appeared relatively homogeneous, the TH‐positive cells of the VLT showed great variations in dendritic branching pattern and orientation. Taken together, the present study has shown that within the RF and the VLT, the TH‐immunoreactive neurons are more numerous than hitherto recognized, and that this cell group consists of a morphologically heterogeneous population of dopamine‐synthesizing neurons.
The thalamostriatal projection in the cat
Authors: Beckstead Robert M.
Published: May 2005

The organization of the projections from the intralaminar and other thalamic nuclei to the caudate nucleus (CD), putamen (PU), nucleus accumbens (Acc), and olfactory tubercle (TO) were examined in the cat by autoradiography after deposits of 3H‐amino acids in individual thalamic nuclei and by retrograde cell labeling after intrastriatal deposits of wheat‐germ‐conjugated horseradish peroxidase.

All of the rostral intralaminar nuclei, here considered to include the central lateral (CL), paracentral (PC), central medial (CeM), and rhomboid nuclei (Rh), project to the striatum. Projections closely associated with those of the rostral intralaminar group arise from cells of the paraventricular nucleus (PV) and a region lateral to the stria medullaris. These nuclei, which roughly form a ring around the mediodorsal nucleus, project in a highly particular, but loosely arranged topographic pattern to all parts of the striatum. The medially located cells in Rh, PV, and those alongside the stria medullaris project mainly to medial parts of Acc and CD; the dorsolaterally located cells of CL project mainly to the dorsolateral parts of CD and PU; cells in PC and CeM project to progressively more ventral and medial parts of CD and PU, and the lateral part of Acc.

Superimposed on this projection from the rostral intralaminar region is the projection from the caudal intralaminar group including the centromedian (CM), parafascicular (PF), and subparafascicular nuclei (subPF). Together these nuclei project in a loosely but specifically organized topography to the entire striatum. The lateral and dorsal parts of CD and PU receive fibers mainly from CM. Ventral and medial parts of CD and PU and Acc receive fibers mainly from PF; TO receives fibers from subPF and the ventral part of PF.

Several nuclei in the lateral nuclear mass of the thalamus also project to particular parts of the striatum. Thus, cells in the rostromedial part of the ventral anterior nucleus project to the head of CD and some cells in the rostral part of the ventromedial nucleus project to the head of CD and to PU. Several cells scattered in the lateral posterior complex project to lateral parts of the head of CD, and cells in the rostral extension of the medial subdivision of the posterior nuclear complex project to lateral parts of the head and body of CD. Finally, several cells of the paratenial nucleus project selectively to Acc.

These data provide a detailed map of the total thalamostriatal projection in the cat and, hence, form a basis for more specific functional questions about this poorly understood system.
Appearance and distribution of neurofilament immunoreactivity in iris nerves
Authors: Seiger Åke , Dahl Doris , Ayer‐LeLievre Christiane , Björklund Håkan
Published: May 2005

We have used antiserum raised against neurofilament (NF) protein and indirect immunofluorescence techniques to visualize neuronal structures in rodent, cat, and cow irides. In the adult rat iris a large population of nerve fibers with a nonautonomic distribution show NF‐like immunoreactivity. In whole mounts, smooth fluorescent fibers were seen in a fine‐meshed plexus from the sphincter margin to the ciliary processes. Superimposed, a sparse pattern of thick meandering axon bundles were seen. Electroblotting and peroxidase immunochemical staining techniques unequivocally showed the presence of all three NF polypeptides in the adult rat iris.

Adult mouse irides showed a somewhat sparser pattern of NF‐positive nerves than that of the rat. Adult guinea pig irides contained irregular NF‐positive fibers and few axon bundles. In cryostat‐sectioned cat iris numerous irregularly distributed individual fibers were found, whereas in similarly sectioned cow iris thick NF‐positive axon bundles were more numerous. By embryonic day 18 numerous sparse NF‐positive axons were seen, and the subsequent gradual increase in both axons in bundles and fine‐meshed plexuses of individual fibers produced an appearance similar to that in the adult by 6 days of postnatal age. One week after grafting of irides to the anterior eye chamber, most NF‐positive nerves had disappeared from the iris grafts. Sympathetic and parasympathetic denervation of the irides did not influence the distribution of the NF‐positive iris nerves. Five days after electrothermal lesion of the trigeminal nerve just distal to its ganglion a large proportion of the NF‐positive nerves had disappeared from the iris. All perikarya in the parasympathetic ciliary and most perikarya in the superior cervical sympathetic and in the trigeminal sensory ganglion showed NF immunoreactivity.

The present report shows a way to visualize nonautonomic nerve populations in stretch‐prepared as well as sectioned irides by immunofluorescence techniques using an antiserum to neurofilament protein.
The ratio of dorsal root ganglion cells to dorsal root axons in sacral segments of the cat
Authors: Chung Kyungsoon , Coggeshall Richard E.
Published: May 2005

Processes of dorsal root ganglion cells are depicted as being unbranched until they reach the spinal cord or periphery. This is an important concept because, for example, branching of these processes might be a basis for referred pain. Recently several studies indicate that axons of rat dorsal root ganglion cells branch in or near the ganglion. The present study extends this work by showing that there are approximately 1.4 dorsal root axons for each dorsal root ganglion cell in sacral segments of the adult cat, and these data are interpreted as indicating that many dorsal root axons in this animal also branch. Thus this study provides further evidence to indicate that a revision of our ideas about the organization of primary sensory cells is desirable.

In addition, this study provides data to indicate that the numbers of both dorsal root ganglion cells and dorsal root axons differ on the right as compared to the left side of the same segment.
Auditory brainstem anomalies in albino cats: II. Neuronal atrophy in the superior olive
Authors: Conlee John W. , Parks Thomas N. , Romero Cardy , Creel Donnell J.
Published: May 2005

In a previous paper (Brain Res., 260:1–9, 1983) we reported that albino cats show abnormal auditory brainstem evoked responses that appear to arise from structural defects in or near the superior olivary complex. In the present study, neuronal cross‐sectional area in brainstem nuclei was compared in albino and normally pigmented adult cats. The albinos were true tyrosinase‐negative (cc) and should not be confused with the deaf white cat (W); the albinos are not deaf. Neurons in the medial superior olivary nucleus (MSO) of albinos were, on average, 41% smaller than in pigmented animals; there was no overlap in the neuronal size distributions for the two groups of animals. Cell size in the lateral superior olive, medial nucleus of the trapezoid body, ventral nucleus of the lateral lemniscus, anteroventral cochlear nucleus, dorsal cochlear nucleus, and facial nucleus was also smaller (by 9–21%) in albinos than in pigmented animals but none of these differences was statistically reliable. In the abducens nucleus, neurons were 12% larger in albinos than in pigmented animals, demonstrating that neuronal size in the albinos is not uniformly smaller. Several lines of evidence suggest that the auditory system defects in albinos are related to abnormal pigmentation rather than to other gene effects. It is possible that a subtle pigment‐related disruption of inner ear development in albinos results in a central cascade of atrophic changes along the auditory pathway.
Quantitative analysis of the dendrites of cat phrenic motoneurons stained intracellularly with horseradish peroxidase
Authors: Cameron William E. , Averill David B. , Berger Albert J.
Published: May 2005

All the dendrites (N = 37) generated by four phrenic motoneurons were analyzed following intracellular injection of horseradish peroxidase. The dendritic arbors produced from each of these stem dendrites were studied in detail. The mean number of stem dendrites produced by a phrenic motoneuron was 9.7, their mean diameter was 6.0 μm, and their mean combined diameter was 58.3 μm. The length at which a phrenic motoneuronal dendrite terminated was 1.236 μm, with several end terminals extending more than 2 mm from the cell body. The mean value for the combined lengths of all segments originating from a single stem dendrite was 5.3 mm. A full spectrum of dendritic branching patterns was observed from simple (five unbranched) to complex, the latter producing up to ninth‐order branches. Most terminal and nonterminal dendritic segments tapered, producing a mean diameter reduction of 34%, or approximately 9% per 100‐μm length. All phrenic motoneurons exhibited a steady decrease in the combined dendritic parameter (Σd3/2) with distance from the soma as a result of tapering and end‐branch termination. The mean surface area and volume of a phrenic motoneuronal dendrite were 35.3 × 103 μm2 and 25.9 × 103 μm3, respectively. The dendrites constituted greater than 97% of the total phrenic motoneuronal surface area, with 75% of this area lying outside of a 300‐μm radius from the cell body.

The diameter of a stem dendrite was positively correlated with its combined dendritic length, number of terminal branches, dendritic surface area, and volume. Despite this strong correlation, the value of total dendritic surface area calculated using the power equation derived from the dendritic surface area versus stem dendritic diameter plot was not a consistent estimator of the total dendritic surface area directly measured for these four phrenic motoneurons. It is suggested that this inconsistency may be the result of a heterogeneity in the phrenic motoneuronal population and/or in the dendrites projecting to the different terminal fields.
Cortical and brain stem afferents to the ventral thalamic nuclei of the cat demonstrated by retrograde axonal transport of horseradish peroxidase
Authors: Nakano Katsuma , Kohno Masako , Hasegawa Yasuo , Tokushige Akinori
Published: May 2005

After horseradish peroxidase (HRP) injections into various parts of the ventral thalamic nuclear group and its adjacent areas, the distribution of labeled neurons was compared in the cerebral cortex, basal ganglia, and the brain stem. The major differences in distribution patterns were as follows: Injections of HRP into the lateral or ventrolateral portions of the ventroanterior and ventrolateral nuclear complex of the thalamus (VA‐VL) produced retrogradely labeled neurons consistently in area 4γ (lateral part of the anterior and posterior sigmoid gyri, lateral sigmoid gyrus and the lateral fundus of the cruciate sulcus), the medial division of posterior thalamic group (POm), suprageniculate nucleus (SG) and anterior pretectal nucleus ipsilaterally, and in the nucleus Z of the vestibular nuclear complex bilaterally.

Injections into the medial or dorsomedial portion of the VA‐VL resulted in labeled neurons within the areas 6aβ (medial part of the anterior sigmoid gyrus), 6aδ (anterior part of ventral bank of buried cruciate sulcus), 6 if. fu (posterior part of the bank), fundus of the presylvian sulcus (area 6aβ), medial part of the nucleus lateralis posterior of thalamus and nucleus centralis dorsalis ipsilaterally, and in the entopeduncular nucleus (EPN) and medial pretectal nucleus bilaterally. Only a few neurons were present in the contralateral area 6aδ.

After HRP injections into the ventral medial nucleus (VM), major labeled neurons were observed in the gyrus proreus, area 6aβ (mainly in the medial bank of the presylvian sulcus), and EPN ipsilaterally, and in the medial pretectal nucleus and substantia nigra bilaterally.

Following HRP injections into the centre médian nucleus (CM), major labeled neurons were found in the areas 4γ, 6aβ, and the orbital gyrus ipsilaterally, and in the EPN, rostral and rostrolateral parts of the thalamic reticular nucleus, locus ceruleus, nucleus reticularis pontis oralis et caudalis and nucleus prepositus hypoglossi bilaterally. The contralateral intercalatus nucleus also possessed labeled neurons. With HRP injections into the paracentral and centrolateral nuclei, labeled neurons were observed in the gyrus proreus and the cortical areas between the caudal presylvian sulcus and anterior rhinal sulcus ipsilaterally, and in the nuclei interstitialis and Darkschewitsch bilaterally. Minor differences in the distribution pattern were observed in the superior colliculus, periaqueductal gray, mesencephalic and medullary reticular formations, and vestibular nuclei in all cases of injections.
The projections of principal cells of the medial nucleus of the trapezoid body in the cat
Authors: Spangler Kevin M. , Warr W. Bruce , Henkel Craig K.
Published: May 2005

Previous studies suggest that the principal cells of the medial nucleus of the trapezoid body (MNTB) give rise to the projection from MNTB to the lateral superior olivary nucleus (LSO) of the same side, where they mediate rapid inhibitory effects of contralateral sound stimulation. In the present study, we explored certain morphological features of this connection as well as several other projections of the MNTB by using anterograde and retrograde axonal tracing methods. Following injections of tritiated leucine into MNTB, labeled axons reached LSO by passing ventral to, dorsal to, and through the medial superior olivary nucleus, and gave rise to labeling around the somata and proximal dendrites of LSO fusiform cells. As measured in autoradiograms of 2 μm plastic sections, these axons had a modal diameter of 5–6 μ. Terminal labeling, tentatively attributed to principal cell axons, was also seen in the ventral nucleus of the lateral lemniscus (VNLL) and the dorsomedial and ventromedial periolivary nuclei. HRP injections into the LSO and the VNLL showed that the prinicpal cell projected to both of these nuclei and revealed a topographic arrangement of the projection to the LSO which is consistent with tonotopic maps determined electrophysiologically. Control HRP injections demonstrated that other minor projections of the MNTB arose from minor cell populations in this nucleus. The findings provide a morphological correlate of certain physiological findings and suggest a wider role for the MNTB in the ascending auditory system than previously has been supposed.
The neuronal composition of area 17 of rat visual cortex. III. Numerical considerations
Authors: Peters Alan , Kara Daniel A. , Harriman Katherine M.
Published: May 2005

The neuronal population of area 17 of rat visual cortex has been examined by using tissue from brains fixed by perfusion. The tissue was osmicated and embedded in plastic so that the same neurons could be examined by both light and electron microscopy. In these preparations area 17 was 1.49 mm thick and by stereological procedures it was calculated that there are about 120,000 neurons beneath 1 mm2 of cortical surface. If one assumes area 17 in each hemisphere of the rat to occupy between 7.1 and 9.4 mm2 of cortical surface, then in each hemisphere the area contains between 850,000 and 1,128,000 neurons. Of these neurons 85% are pyramidal cells and 15% are nonpyramidal cells. About one‐third of the nonpyramidal cells occur in layers I and VIb, both of which contain only this kind of neuron. The remaining two‐thirds of the nonpyramidal cells are in layers II‐VIa. Within these layers it has been possible to differentiate bipolar cells from other types of nonpyramidal cells and in each of these two nonpyramidal cell groups to recognize both small and large neurons. The greatest concentration of nonpyramidal cells occurs in layer II/III. To confirm the validity of the stereologically derived data direct counts were made of the medium and large pyramidal cells in layer V.
Dendrite distribution of identified motoneurons in the lumbar spinal cord of the turtlePseudemys scripta elegans
Authors: Ruigrok T. J. H. , Crowe A. , ten Donkelaar H. J.
Published: May 2005

Motoneurons in the turtle lumbar spinal cord were injected with HRP by electrophoresis after being electrophysiologically identified as innervating a muscle belonging to a functional group. The distribution of dendrites was studied in transverse reconstructions of 45 motoneurons, including motoneurons identified as innervating knee extensor muscles, eight motoneurons innervating hip retractor and knee flexor muscles, 14 motoneurons innervating ankle and/or toe extensors and 12 motoneurons innervating ankle and/or toe flexor muscles.

The dorsal dendritic tree of motoneurons innervating distally positioned musculature (ankle and/or toe extensors and flexors) was observed to contain significantly less terminal dendritic branches compared to the dorsal dendritic trees of motoneurons innervating proximally situated (hip and knee) muscles.

The distribution of dendrites within the white matter was studied by measuring the total projected length of the dendritic branches within empirically defined sectors in the transverse plane. This kind of analysis also revealed differences between the dorsal dendrites of motoneurons innervating distally and proximally positioned muscles conforming to the counts of terminal dendritic branches. It is suggested that these apparent differences in the size of the dorsal dendrite may be related to the number of synapses made by primary afferents.

In the white matter, the highest dendritic density for all four groups of mononeurons was found within the central part of the lateral funiculus. However, only in the ventral funiculus could slight indications be found that the dendritic density of functionally different motoneuron groups may bear some relation to the locations of the terminations of the descending pathways known to establish monosynaptic contacts with lumbar mononeurons.
Unmyelinated primary afferent fibers in dorsal funiculi of cat sacral spinal cord
Authors: Chung Kyungsoon , Coggeshall Richard E.
Published: May 2005

The present study tests the hypothesis that there are numerous unmyelinated primary afferent fibers in cat posterior funiculi. The animals have unilateral dorsal rhizotomies from L6 to Ca3. One week later the axons of both S2 dorsal funiculi are counted. The data indicate that there are approximately 22,500 myelinated and 8,500 unmyelinated axons on the unoperated side and 11,000 myelinated and 3,900 unmyelinated axons on the operated side. On this basis we suggest that 51% of the myelinated and 54% of the unmyelinated axons in cat dorsal funiculi arise from dorsal root ganglion cells and thus are primary afferent axons. If this is correct, then 71% of the primary afferent axons in the cat dorsal funiculus are myelinated and 29% are unmyelinated. The function of this large group of previously unsuspected fine sensory axons remains to be determined.
I. Cytology and distribution in normal human cerebral cortex of neurons immunoreactive with antisera against neuropeptide Y
Authors: Chan‐Palay V. , Allen Y. S. , Lang W. , Haesler U. , Polak J. M.
Published: May 2005

The frontal, parietal, and temporal cortices in normal human brains (Brodmann areas 10, 7a, 7b, and 21) are well endowed with numerous neurons, identifiable by immunoreactivity with antisera against the 36‐amino acid brain peptide neuropeptide Y (NPY). These neurons with rare exception are small, intracortical, nonspiny neurons, 12–20 μm in somatic size, with long slender dendrites and exuberant axon plexuses exhibiting finely beaded varicosities. The cells are rarest in layers I and II, are found with frequency in the lower cortical layers (IV‐VI) and in significant numbers in the subcortical white matter. Within the cortex the axonal plexuses of these peptide neurons rise straight up into the upper cortical layers or descend deep into the white matter. In layers I and II, numerous other lengthy axons, some possibly of extracortical afferent origin, run along the pial surface at right angles to the axial ones running perpendicular to the cortex. This endowment of peptide neurons and their processes forms a rich network in the cerebral cortex, relating with one another in complex fashion within palisades of terminals as well as with the other cortical neurons not labeled by these methods. It remains to be shown what functions these NPY neurons have individually and in their remarkable networks, and how they are altered in neurological disease.