bluuebunny/crossref_metadata_2025 huggingface dataset:
Septotemporal distribution of entorhinal projections to the hippocampus in the cat: Electrophysiological evidence
Authors: Van Groen Th. , Da Silva F. H. Lopes
Published: January 2005

The projection of the entorhinal cortex (EA) to the hippocampus in the cat has been studied by electrophysiological methods. Field potentials elicited by EA stimulation sites were measured in the hippocampus (fascia dentata). Different topographic distributions of the amplitude and of the onset latency of average evoked potentials (AEPs) were obtained depending on the place of the stimulation along a lateromedial axis in the Ea. The lateral EA elicited the largest AEPs in the septal part of the hippocampus and the medial EA evoked maximal responses in the temporal part of the hippocampus, while the intermediate part of the EA evoked the largest AEPs in the splenial (intermediate) part of the hippocampus. Unit activity elicited by hippocampal stimulation was measured in the EA. Analysis of the antidromic unit activity showed that the pathways analysed were monosynaptic. Different conduction velocities to the septal part of the hippocampus were found; the pathway from the lateral EA was the fastest and the pathway from the medial EA the slowest. Assuming that the sites of maximal AEP amplitude correspond to the location of the major synaptic inputs, it can be conduced that the active synaptic inputs arising along a lateromedial axis in the EA are distributed within the hippocampus according to a septotemporal axis, although with some overlap between the different projections. Therefore it may be concluded that the hippocampus is not homogeneous with respect to the inputs from the EA. The present observations are discussed regarding anatomical data and putative functional differences between septal and temporal hippocampus.
Central somatostatin systems revealed with monoclonal antibodies
Authors: Vincent S. R. , McIntosh C. H. S. , Buchan A. M. J. , Brown J. C.
Published: January 2005

The distribution of central neurons displaying somatostatin immunoreactivity was studied using three monoclonal antibodies to cyclic somatostatin. The sensitive ABC immunoperoxidase technique was employed. A large number of positive cell groups including many previously undescribed populations were detected throughout the brain and spinal cord. Telencephalic somatostatin neurons included periglomerular cells in the olfactory bulb, mitral cells in the accessory olfactory bulb, and multipolar cells in the anterior olfactory nuclei, neocortex, amygdala, hippocampus, lateral septum, striatum, a ad nucleus accumbens. Within the hypothalamus, positive neurons were found in the periventricular, suprachiasmatic, and arcuate nuclei, and throughout the anterior and lateral hypothalamus. The entopeduncular nucleus and zona incerta contained many positive neurons, and the lateral habenula had a dense terminal field suggesting a pallidohabenula somatostatin pathway.

Somatostatin neurons were also found in association with many sensory systems. Positive cells were present in the superior and inferior colliculi, the ventral cochlear nuclei, the ventral nucleus of the lateral lemniscus, nucleus cuneatus, nucleus gracilus, and the substantia gelatinosa.

Various cerebellar circuits also displayed somatostatin immunoreactivity. Golgi cells throughout the cerebellar cortex were intensely stained, and some Purkinje cells in the paraflocculus also showed a positive reaction. Positive fibers were present in the granular layer and large varicose fibers were present in the inferior cerebellar peduncle. Many nuclei known to project to the cerebellum, including the nucleus reticularis tegmenti pontis, the medial accessory inferior olive, the nucleus prepositus hypoglossi, and many areas of the reticular formation contained positive neurons.

These studies demonstrate that these new monoclonal antibodies are of great value for the study of central somatostatin systems. Previously described somatostatin systems are readily detected with these antibodies, and in addition, many otherwise unrecognized somatostatin cell groups have been discovered.
Cytochrome oxidase staining in the rat smI barrel cortex
Authors: Land Peter W. , Simons Daniel J.
Published: January 2005

Patterns of cytochrome oxidase (CO) activity were examined histochemically in the rat SmI cortex. Discrete regions of high enzymatic activity were centered upon the granule cell aggregates (barrels) in layer IV. Those barrels which correspond to the mystacial vibrissae and make up the posteromedial barrel subfield (PMBSF) were especially interesting in that CO staining revealed distinct metabolic subdivisions which do not have an easily demonstrable cytoarchitectonic counterpart. By analogy with the barrels in mouse PMBSF and with the cytoarchitectonically distinct barrels representing the smaller sinus hairs in the rat we propose that regions of high CO activity denote the “hollow” of the rat PMBSF barrels.

In accord with previous physiological studies demonstrating a vertical organization in the rodent barrel cortex, we also noted columns of intense CO activity extending from layer VI through sublamina Vb. The centers of these columns coincided with the centers of the barrels in layer IV. In tangential sections through the infragranular laminae the segmentation of CO‐positive zones was less distinct than in layer IV and appeared as bands of heightened activity oriented like the five rows of layer IV barrels. Highly reactive somata, and dendrites were observed in both the granular and infragranular CO barrels indicating that some of the increased activity of these regions reflects oxidative metabolism of cortical neurons per se. These patterns of metabolic activity underscore the vertical and horizontal organization of the SmI vibrissa cortex and suggest that neurons located within the central core of a column have functional properties distinct from those located in zones where individual columns interface.
Plasticity in the rat olfactory cortex
Authors: Westrum L. E. , Bakay R. A. E.
Published: January 2005

The relationship of age to deafferentation plasticity was studied in the rat olfactory cortex (OC). Ablation of a single olfactory bulb (OB) was performed in each of several rats of selected postnatal (PN) ages: PN2.5, 6, 9, 13, and 21 days and in adults of PN100 days. Following survival times sufficient to remove the resultant degeneration, a cortical lesion was placed in the ipsilateral OC. The patterns of degeneration from the OC lesion were studied and mapped in the, adjacent deafferented OC. The results show a spread or sprouting of the usually deep‐lying afferents (interrupted by the OC lesion), onto the deafferented superficial dendrites (normally occupied by the OB afferents) in all of the ages. The spread is most striking at PN2.5 to PN9, gradually reduced by PN13 to PN21, and least in the adult (PN100). There is also an apparent increase of afferents to the deeper dendrites nearer the cell bodies in all cases except in the PN 100 group. Shrinkage of layer I is not seen in PN2.5 subjects, is minimal by PN9, but is most marked in the adult PN100 with total OB lesions. Incomplete OB lesions sparing some lateral olfactory tract (LOT) fibers greatly reduce the shrinkage of layer I and the spread of afferents in all ages. Thus, a capacity for reorganization of afferents occurs at least through PN9, with PN13‐21 a possible “critical period” after which plasticity is limited and transneuronal effects are more permanent. The association, centrifugal, and olfactory‐entorhinal pathways are possible origins for this plasticity. Factors contributing to limitations in this reorganization are discussed.
Structure‐function relationships in rat brainstem subnucleus interpolaris. I. Vibrissa primary afferents
Authors: Jacquin Mark. F. , Woerner Diane , Szczepanik Ann Marie , Riecker Virginia , Mooney Richard D. , Rhoades Robert W.
Published: January 2005

Intra‐axonal recording and horseradish peroxidase labelling techniques were used to examine structure‐function relationships for vibrissa‐sensitive primary afferent fibers (N = 40) in rat trigeminal brainstem subnucleus interpolaris (SpVi). All responded at short (mean‐0.42 ms) latencies to trigeminal ganglion shocks and to innocuous stimulation of an individual vibrissa in a slowly adapting type I, slowly adapting type IIa, slowly adapting type IIb, low‐velocity‐sensitive rapidly adapting, or high‐velocity‐sensitive rapidly adapting fashion. As in the medullary dorsal horn (Hayashi, '82; Jacquin et al., '86a), functionally distinct mystacial vibrissae‐related fibers were morphologically indistinguishable. Each gave rise to up to ten collaterals that entered interpolaris perpendicular to the long axis of the nucleus and often overlapped to form a densely packed, highly circumscribed, and largely continuous column of terminal arbors. While some morphological variability was observed both within and between individual axons, variance within a given functional class was no greater than that between classes. Nonmystacial vibrissae afferent arbors also formed similar ovoid, dense circumscribed terminal plexuses. Presumably, these individual arbors collectively form a longitudinal tubelike vibrissae representation in this and other components of the trigeminal brainstem nuclear complex.

The relative locations of each fiber's terminal field could be accurately predicted by the particular vibrissa innervated. Contrary to previous data obtained with similar methods (Hayashi, '82), but consistent with the findings of earlier transganglionic tracing (Arvidsson, '82) and histochemical (Belford and Killackey, '79) studies, the arbors of these fibers terminated throughout the mediolateral extent of SpVi. Axons innervating rostral vibrissae terminated medially, and those that supplied caudal vibrissae innervated the lateral SpVi. Dorsal vibrissae were represented in the ventral SpVi, while ventral vibrissae were represented more dorsally. This transverse topography extended largely throughout the rostrocaudal extent of interpolaris. In summary, the vibrissae primary afferent map in SpVi is inverted, faces medially, and is rostrocaudally consistent. In its most caudal aspect, as the displaced substantia gelatinosa swings laterally, the map is less orderly and incomplete. These generalizations also apply to the nonmystacial vibrissae afferents.
Mapping of proctolinlike immunoreactivity in the nervous systems of lobster and crayfish
Authors: Siwicki Kathleen K. , Bishop Cynthia A.
Published: January 2005

Whole‐mount immunocytochemical techniques have been used to map candidate proctolin‐containing cells in the central nervous systems of the lobster, Homarus americanus, and the crayfish, Procambarus clarkii. Proctolinlike immunoreactivity was detected in cell bodies and neuropil regions in all central ganglia, and immunoreactive axons were detected in most interganglionic connectives and nerve roots. Cell body staining was confined to fewer than 2% of all cells. Immunoreactive neurons include motoneurons, sensory 'neurons, neurosecretory cells, and interneurons. Colocalization of the proctolinlike antigen with other neurotransmitters was indicated in a number of cases. Many aspects of the distribution of immunoreactivity were similar in lobster and crayfish; however, staining differences were detected in a number of identified neurons and neural groups, including neurons that innervate the pericardial organs and hindgut motoneurons. Further studies of such neurons might provide interesting clues about the physiological functions of proctolin and the evolution of peptide transmission.
Modulatory action and distribution of the neuropeptide proctolin in the crustacean stomatogastric nervous system
Authors: Marder Eve , Hooper Scott L. , Siwicki Kathleen K.
Published: January 2005

Immunocytochemical methods were used to map the distribution of proctolinlike immunoreactivity in the stomatogastric nervous systems (stomatogastric ganglion (STG), paired commissural ganglia (CG), oesophageal ganglion (OG), and connecting nerves) of three crustacean species: Panulirus interruptus, Cancer borealis, and Homarus americanus. Although the patterns of proctolinlike staining were similar among the three species, some differences were also observed. Over 70% of the proctolinlike material in STGs, as measured by radioimmunoassay, was indistinguishable from authentic proctolin in reverse‐phase high‐performance liquid chromatography. Bath application of proctolin to STGs from Cancer and Panulirus induced characteristic and robust (though somewhat different) changes in their motor patterns. The threshold concentration was approximately 10−9M proctolin, and the effects were dose‐dependent. These data suggest that the neuropeptide proctolin serves as a neuromodulator of the stomatogastric ganglion.
Cholinergic and GABAergic afferents to the olfactory bulb in the rat with special emphasis on the projection neurons in the nucleus of the horizontal limb of the diagonal band
Authors: Záborszky L. , Carlsen J. , Brashear H. R. , Heimer L.
Published: January 2005

We have examined the location of cholinergic and GABAergic neurons that project to the rat main olfactory bulb by combining choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) immunohistochemistry with retrograde fluorescent tracing. Since many of the projection neurons are located in subcortical basal forebrain structures, where the delineation of individual regions is difficult, particular care was taken to localize projection neurons with respect to such landmarks as the ventral pallidum (identified on the basis of GAD immunoreactivity), the diagonal band, and medial forebrain bundle. In addition, sections with fluorescent tracers or immunofluorescence were counterstained for Nissl substance in order to correlate tracer or immunopositive neurons with the cytoarchitecture of the basal forebrain.

The majority of the cholinergic bulbopetal neurons are located in the medial half of the nucleus of the horizontal limb of the diagonal band (HDB), whereas only a few are located in its lateral half. A substantial number of cholinergic bulbopetal cells are also found in the sublenticular substantia innominata. A small number of cholinergic bulbopetal neurons, finally, are located in the ventrolateral portion of the nucleus of the vertical limb of the diagonal band. At the level of the crossing of the anterior commissure, approximately 17% of the bulbopetal neurons in the HDB are ChAT‐positive. The noncholinergic bulbopetal cells are located mainly in the lateral half of the HDB.

GAD‐containing bulbopetal neurons are primarily located in the caudal part of the HDB, especially in its lateral part. About 30% of the bulbopetal projection neurons in the HDB are GAD‐positive. A few GAD‐positive bulbopetal cells, furthermore, are located in the ventral pallidum, anterior amygdaloid area, deep olfactory cortex, nucleus of the lateral olfactory tract, lateral hypothalamic area, and tuberomamillary nucleus.

The topography of bulbopetal neurons was compared to other projection neurons in the HDB. After multiple injections of fluorescent tracer in the neocortex, retrogradely labeled neurons were concentrated in the most medial part of the HDB, while neurons projecting to the olfactory and entorhinal cortices were located in the ventral part of the HDB. These results show that the cells of the HDB can be divided into subpopulations based upon projection target as well as transmitter content. Furthermore, these subpopulations correspond, at least to a considerable extent, to areas that can be defined on cyto‐ and fibroarchitectural grounds.
Age‐Dependent occurrence of an ascending axon on the omega neuron of the cricket, Teleogryllus oceanicus
Authors: Atkins Gordon , Pollack Gerald S.
Published: January 2005

The omega neurons (ON1s) are a mirror‐symmetrical pair of identified prothoracic auditory interneurons of crickets which have been previously described as intraganglionic. Using intracellular techniques we stained ON1s of female Teleogryllus oceanicus and found that many ON1s have axons which project anteriorly out of the prothoracic ganglion. The ascending axon arises contralateral to the soma at the most anteriolateral bend of the bowshaped process of an otherwise “archetypical” ON1 and travels up the neck connective in a ventral position just inside the connective tissue sheath. The occurrence of the ascending axon is age‐dependent. Seventy‐five percent of ON1s stained in late nymphal stages and in young adults had an ascending axon while only 30% of ONis in older adults had an ascending axon. Evidence is presented to show that ON1s having ascending axons are developmental variants of the “archetypical” ON1 and do not represent a separate neuron type. The two morphological types of ON1s are not distinguishable on the basis of their responses to sound stimuli having carrier frequencies of 3.5‐60 kHz. Although we know that the ascending axon conducts action potentials, its target and terminal morphology are not yet known.
Oral and facial representation in the trigeminal principal and rostral spinal nuclei of the cat
Authors: Shigenaga Yoshio , Okamoto T. , Nishimori T. , Suemune S. , Nasution I. D. , Chen I. C. , Tsuru K. , Yoshida A. , Tabuchi K. , Hosoi M. , Tsuru H.
Published: January 2005

Transganglionic transport of horseradish peroxidase (HRP) was used to study the patterns of termination of somatic afferent fibers innervating oral and facial structures within the principal nucleus (Vp), nucleus oralis (Vo), and nucleus interpolaris (Vi). The primary trigeminal afferent fibers that innervate the oral cavity supplied by the pterygopalatine, superior alveolar, lingual, buccal, and inferior alveolar branches, as well as the facial skin sunnlied by the frontal, corneal, zygomatic, infraorbital, auriculotemporal, mylohyoid, and mental branches, were traced in this experiment. The results show that trigeminal afferent nerves that innervate the oral cavity project mainly to the principal nucleus, the rostrodorsomedial part (Vo.r) and dorsomedial division (Vo.dm) of pars oralis, and the dorsomedial region of pars interpolaris, while an extensive overlap of projections is found in the Vo.r, Vo.dm, and rostral Vi. The central processes of fibers innervating the anterior face (i.e., mental, infraorbital, and frontal nerves) terminate in the ventral division of principalis (Vpv), caudal region pars oralis (Vo.c), and ventrolateral Vi, with the largest numbers of terminals being found in the Vpv and Vi. In contrast, the central projection patterns of the corneal, zygomatic, mylohyoid, and auriculotemporal afferents are different from those of other afferent nerves examined, and present a discrete projection to the trigeminal sensory nuclear complex (TSNC). The corneal, mylohyoid, and auriculotemporal afferents mainly project to the restricted regions of principalis and caudal Vi, while zygomatic afferent nerve fibers project to the caudal third of pars interpolaris. The typical somatotopic organization with the face of the mouth open inverted is represented in the rostrocaudal midlevels of the Vpv and caudal pars interpolaris. The Vpd receives topographical projection from primary afferent nerves that innervate the oral structure only, while this projection was organized in a complicated manner. The relationship between the functional segregation and the cytoarchitectonic differentiation of the TSNC is discussed, particularly with respect to this somatotopic organization, combined with the characteristics of projecting cells in the TSNC.
A Golgi study of the neuronal population of the marginal zone (lamina I) of the rat spinal cord
Authors: Lima Deolinda , Coimbra Antonio
Published: January 2005

On the basis of dendroarchitecture and cell body shape, complemented with morphometry of dendritic ramification, four major neuronal types were distinguished in lamina I of the spinal cord of the rat. (I) Fusiform spiny cells (39% of impregnated neurons) have longitudinal spindle‐shaped perikarya with bipolar, less frequently unipolar, dendritic trees rich in pedicled spines and a thin, beaded longitudinal axon; such neurons occur mainly in the lateral marginal zone. In type IA cells (33% of the total), the dendritic domain occupies a narrow longitudinal area, while in type lb cells (6%) the polar dendritic trees partly arborize ventrally. Fusiform neurons are considered intrinsic cells connected with the longitudinal afferent plexus in lateral lamina I, and in type IB cells also receiving primary input in the substantia gelatinosa. (II) Multipolar cells (23%) have a dense dendritic arbor originating from numerous primary trunks and they predominate in the medial marginal zone. The dendritic arbor is moderately extended dorsoventrally in type IIA cells and reaches lamina III in the larger type JIB cells. The former possess a variety of spines, axonlike processes and sometimes an unmyelinated axon, and are presumably interneuron's, while type IIB cells show a thick tapering axon that is probably myelinated. (III) Flattened aspiny neurons (13%) with a polygonal body flattened in the horizontal plane, and a horizontal dendritic arbor confined to lamina I; these cells predominate in middle lamina I. (IV) Pyramidal neurons (25%) have longitudinally elongated perikarya that bulge into the white matter. The arbor has a large longitudinal and lateromedial spread and includes branches which ramify in the white matter. Types III and IV show the classical lateromedially elongated orientation of the marginal cells of the old literature; they show thick tapering axons and probably make up the bulk of the projection neurons of rat lamina I.
Mauthner neurons survive metamorphosis in anurans: A comparative HRP study on the cytoarchitecture of Mauthner neurons in amphibians
Authors: Will Udo
Published: January 2005

Giant medullary neurons were revealed in adult Xenopus laevis and Rana esculenta following HRP injections to the spinal cord. These neurons were identified as Mauthner neurons because (1) they have the same position and orientation as the larval Mauthner neurons, i.e., they lie at the level of the VIIIth nerve root. (2) they have two large dendritic trees that for each species are similar to those of the larval Mauthner neurons, (3) they are clearly distinguishable from other large reticular neurons, (4) they have close connections with the VIIIth nerve afferents, (5) they have a decussating descending axon, the largest of the adult brainstem, and (6) they have a reduced axon cap, i.e., a dense neuropil without cap dendrites.

Mauthner neurons were also identified in adult Xenopus muelleri, Hymenochirus curtipes, Hyla cinerea, Rhacophorus leucomystax, and Kalula pulchra.

No Mauthner neuron was identified in larval or adult Bombina bombina or Bufo bufo or in adult Bufo terrestris, Bombina orientalis, or Scaphiopus holbrookii.

Cytoarchitecture and the elaborate dendritic trees were also revealed in urodeles. Mauthner neurons of terrestrial forms (Ambystoma tigrinum, Paramesotriton chinensis) exhibit a less‐extensive branching of the “lateral line” dendrite but otherwise show no signs of involution or regression compared to aquatic forms (Siredon mexicanum, Cynops pyrrhogaster).

No Mauthner neuron was identified in larval or adult Ichthyophis kohtaoensis.

Besides the topographical relations between Mauthner neurons and afferent fibers from the lateral line and the VIIIth nerve we could demonstrate a projection of trigeminal and mesencephalic neurons onto the soma of the amphibian Mauthner neuron.
Choline acetyltransferase immunoreactivity suggests that ganglion cells in the goldfish retina are not cholinergic
Authors: Tumosa N. , Stell W. K.
Published: January 2005

Published evidence that ganglion cells in the retinae of nonmammalian species are cholinergic is strong but indirect. In this paper we report results of attempts to demonstrate choline acetyltransferase immunoreactivity in ganglion cells of goldfish retina using two different antisera against choline acetyltransferase (ChAT), the acetylcholine‐synthesizing enzyme.

We obtained ChAT‐immunoreactive staining of amacrine and displaced amacrine cells in the retina and type XIV cells in the tectum, but we obtained no direct immunocytochemical evidence that ganglion cells in the goldfish retina are cholinergic. Thus, ganglion cells identified by retrograde transport of propidium iodide were never ChAT‐immunoreactive. Intraocular injections of colchicine did not result in the appearance of a population of ChAT‐immunoreactive neurons in the ganglion cell layer. ChAT‐immunoreactive axons were not observed in intact, ligated, or transected optic nerves. And finally, the ChAT immunoreactivity of cells and fibers in the optic tectum was unaffected by deafferentation.

These experiments provide no positive evidence that any ganglion cells in goldfish retina contain the acetylcholine‐synthesizing enzyme, ChAT. While it is possible that our method is too insensitive to detect the enzyme in ganglion cell somata or too specific to recognize the form of ChAT present in these cells, the fact that we can stain putatively cholinergic retinal amacrine cells and tectal neurons makes these alternative explanations improbable. We conclude that it is unlikely that any of the ganglion cells in the retina are cholinergic and that alternative explanations should be sought for previously published results that suggest that they are.
Distribution of immunoreactive somatostatin (ISRIF) in the nervous system of the squid, Loligo pealei
Authors: Feldman Susan C.
Published: January 2005

Somatostatin (SRIF) is a neuropeptide with a ‐widespread distribution in the mammalian CNS. In the present study we have examined the distribution of immunoreactive‐like SRIF (ISRIF)‐containing elements in the nervous system of the cephalopod mollusk Loligo pealei or the Woods Hole squid. ISRIF was localized by light immunocytochemistry in sections of the squid—optic lobe, circumesophageal ganglia—and in stellate ganglion. In the optic lobe, ISRIF neurons were found in the internal granule cell layer and medulla and immunoreactive fibers were seen throughout the lobe and in the optic tract but were absent from the optic nerve, i.e., the projection between the retina and optic lobe. In the supraesophageal complex, ISRIF neurons were found in all lobes, but primarily in the vertical, subvertical, and frontal. In the subesophageal ganglion, ISRIF neurons were seen mainly following unilateral pallial nerve lesions; these neurons were primarily small‐to‐medium sized. ISRIF fibers were seen in many of the nerves exiting from the brain and in nerves extending between the sub‐ and supra‐esophageal ganglia. In the stellate ganglion, ISRIF was present in many neurons as well as in a plexus of fibers within the ganglion; the peptide was absent from the second‐order fibers and the giant axon.

The data suggest that a molecule immunologically similar to vertebrate SRIF may be a major transmitter/modulator in this invertebrate. These results provide a foundation for further studies to evaluate the role of this molecule.
Plasticity in the olfactory cortex: Age‐dependent effects of deafferentation
Authors: Friedman Beth , Price J. L.
Published: January 2005

In order to assess the role of input‐target interactions in the development of olfactory ccrtex, the primary afferent fibers from the olfactory bulb to the superficial part of layer I of the cortex (layer Ia) were removed in developing and mature rats. After survival periods that vary from a few days to 2–6 months, changes were assessed in (1) the radial thickness of layer I, (2) the laminar distribution of intracortical associational fibers, which normally terminate in a deep part of layer I (layer Ib), and (3) the distribution of glia in layer I. The findings indicate that the lamination of fibers within layer I is not intrinsically prespecified, but gradually becomes “set” during the first month after birth. If the fibers from the olfactory bulb are removed, the dendrites of cortical cells are capable of accepting inputs from other fiber systems, depending on the maturational state of the dendrites and the ingrowing axons. Development of the abnormal inputs is associated with relatively normal dendritic growth, whereas lack of adequate input results in dendritic atrophy.

Thus, after neonatal bulb ablation, the intracortical fibers occupy both superficial and deep parts of layer I, and a normal synaptic density is established throughout the layer. Layer I also develops to nearly its normal adult thickness, although the high density of glia that normally characterizes layer Ia is not apparent. With bulb ablation at progressively older ages (from postnatal day (P‐) 3 to 21), the cortical associational fibers show progressively less extension into the denervated layer Ia. Layer I continues to grow, but rut to the same extent as after P‐1 ablations. In these experiments the glia distribution resembles the pattern present at the time of denervation. After adult olfactory bulb albation, the long intracortical fibers extend very little into layer Ia, which undergoes pronounced shrinkage and becomes filled with a high concentration of glia. However, partial reinnervation of layer Ia is accomplished by the proliferation of a normally sparse native fiber system, which has been identified only with the Timm method.

These results are interpreted as evidence that the normal development of lamination of afferent fibers to the olfactory cortex depends on axodendritic interaction during development.
Age‐dependent cell death in the olfactory cortex: Lack of transneuronal degeneration in neonates
Authors: Friedman B. , Price Joseph L.
Published: January 2005

Adult olfactory cortical neurons in layer IIa undergo fulminant transneuronal degeneration after removal of afferent olfactory bulb fibers (Price, '76, Neurosci Abst. 2:161; Heimer and Kalil, '78, J. Comp. Neurol 178:559‐609). This provides an unusual example of dependence of a mature population of neurons on axonal input. In order to investigate whether similar transneuronal degeneration occurs in immature animals, a series of rats were subjected to unilateral olfactory bulb removal at various ages during the first 3 postnatal weeks. The brains were examined for degeneration after short survivals by use of the de Olmos cupric silver method, which selectively stains degenerating neurons. In addition, animals with long survivals were examined with the HRP retrograde tracing method, in order to determine if cells that survive the acute effects of deafferentation develop normal patterns of connections.

Young neurons are more resistant to the effects of olfactory bulb removal than more mature neurons. There was little degeneration of cortical neurons after bulb ablation during the first 2 postnatal, weeks. Although layer IIa does not become distinct from layer IIb in, these experimental animals, cells that have connections normally characteristic of the cells of layer IIa, and are situated at the superficial edge of layer II, were identified with the HRP method. The severity of transneuronal degeneration increases and becomes adultlike between the second and third postnatal weeks. This increase in transneuronal degeneration is temporally associated with a progressive reduction in axonal sprouting following deafferentation during the first 3 postnatal weeks, as described in the companion paper (Friedman and Price, '86). Thus, axon sprouting may “protect” the immature IIa neurons from the effects of removal of the fibers from the olfactory bulb.

A period of normal cell death has also been identified in olfactory cortex by the use of the de Olmos cupric silver method. This cellular degeneration is much less severe and has a different time course and laminar distribution than the transneuronal degeneration produced by olfactory bulb ablation in adults. Although normal cell death appears to be potentiated by removal of the olfactory bulb on postnatal day 1, it is clearly a different process from the transneuronal reaction.
Identification of distinct topographical distributions of lumbar sympathetic and sensory neurons projecting to end organs with different functions in the cat
Authors: Jänig W. , McLachlan Elspeth M.
Published: January 2005

A comparison has been made between the lumbar sensory and sympathetic pre‐ and postganglionic neurons that project in the lumbar splanchnic nerves and those that project in the caudal lumbar sympathetic trunk of the cat. The neuron cell bodies have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons near the inferior mesenteric ganglion on one side, and the results have been compared with those obtained after labeling the contralateral lumbar sympathetic trunk of the same animal (Jänig and McLachlan, '86). The numbers, segmental distribution, location, and size of the labeled somata have been determined quantitatively. The data for individual animals confirm in every way those previously reported for separate experiments in different groups of animals. In addition, similar experiments were performed in which the neurons projecting in the white rami of either L4 or L5 were labeled. This procedure labeled populations of neurons that overlapped both splanchnic and paravertebral populations. Consideration of the spatial distributions and numbers of sensory and preganglionic neurons with destinations in somatic and visceral domains has enabled us to describe the different topography of these neuron populations with respect to function.
Single thalamic neurons project to both lateral suprasylvian visual cortex and area 17: A retrograde fluorescent double‐labeling study
Authors: Tong Lillian , Spear Peter D.
Published: January 2005

Area 17 and the posteromedial lateral suprasylvian (PMLS) visual cortex receive inputs from three thalamic nuclei in common: the lateral division of the lateral posterior nucleus (LPI), the C‐laminae of the lateral geniculate nucleus (LGNd), and the medial interlaminar nucleus (MIN). The present study determined whether these projections originate from the same cells via bifurcating axons or from separate populations of cells. Double‐label retrograde transport techniques were used to label cells projecting to area 17 with one fluorescent dye and to label cells projecting to PMLS cortex with a different dye. The two dyes used were fast blue and Evans blue. Following injections into the two cortical areas, some cells were double labeled and some were single labeled in all three thalamic nuclei studied. However, the relative number of double‐ and single‐labeled cells, as well as the relative number of cells single‐labeled following injections into each cortical area, differed among the three thalamic nuclei. In both MIN and the C‐laminae of the LGNd, the number of double‐labeled cells was small. Similarly, the number of cells single labeled with the dye placed in PMLS cortex was small in these two nuclei. In contrast, a relatively large number of cells were single labeled with the dye placed in area 17, especially in the C‐laminae of the LGNd. These results suggest that in both MIN and the C‐laminae of the LGNd, few cells project to both area 17 and the PMLS cortex, few cells project only to PMLS cortex, and a relatively greater number of cells project only to area 17. In LPl, many cells were labeled after the cortical injections. In fact, when the areas of densest labeling for both dyes overlapped, almost every labeled cell in LPl was double labeled. This indicates that almost all LPl cells that project to one cortical area also project to the other via a bifurcating axon.
The visual system of the channel catfish (ictalurus punctatus). I. Retinal ganglion cell morphology
Authors: Dunn‐Meynell A. A. , Sharma S. C.
Published: January 2005

Horseradish peroxidase was applied to lesions in the optic nerve of catfish (Ictalurus punctatus). The retinae were processed to reveal HRP‐labelled ganglion cells. The histochemical techniques employed allowed fine details of the dendritic arbor to be resolved. Flat‐mounted retinae were examined and the following characteristics were noted in individual ganglion cells: Soma area, shape, and depth; number and diameter of major dendrites; shape, area, and depth(s) within the inner plexiform layer (ipl) of the dendritic arbor; origin of the axon (from the soma or a dendrite). On the basis of these characteristics, eleven classes of ganglion cells were delineated: four classes of giant cells (Gl‐G4) and seven classes of smaller cells (Sl‐S7). G1 cells had dendrites arborizing in the most distal sublamina of the ipl. G1 cells in the dorsal retina had nasotemporally elongated dendritic arbors. G2 cells had dendrites in the proximal portion of the ipl. G3 cells were almost completely confined to a band running between the nasal and temporal retinal poles, through the center of the retina. In this location, the cells had dorsoventrally elongated dendritic arbors, which were bistratified in the ipl. G4 cells were displaced into the inner nuclear layer. S1 and S4 cells had axons arising from their somata, and dendrites arborizing in the distal and the proximal ipl, respectively. S2 cells were typified by their unstratified dendritic arbors. Similarly, S3 cells were characterised by their bistratified arbors. S5 cells arborized in the most proximal ipl sublamina. S6 cells were small ganglion cells with their somata lying in the inner nuclear layer. S7 cells tended to have complex dendritic arbors, and their axons arose from dendrites.
The facial “motor” nerve of the rat: Control of vibrissal movement and examination of motor and sensory components
Authors: Semba Kazue , Egger M. David
Published: January 2005

Rhythmical whisking of the mystacial vibrissae at about 7 Hz during exploration is one of the most conspicuous behavioral patterns in the rat. To identify the final common pathway for vibrissal movement, individual motor branches of the facial nerve, including the posterior auricular, temporal, zygomatic, buccal, marginal mandibular, cervical, stylohyoid, and posterior digastric branches, were cut, either singly or in various combinations. We found that vibrissal movement could be abolished only by transection involving the buccal branch and the upper division of the marginal mandibular branch.

To trace back the central origins of the buccal and marginal mandibular, as well as the other branches of the facial nerve, all distal to the stylomastoid foramen, horseradish peroxidase (HRP) was applied to the cut proximal ends of these individual branches. The retrograde HRP labelling in the facial motor nucleus revealed topographical representation of these branches in which the buccal and marginal mandibular branches were represented laterally. The stylohyoid and posterior digastric branches originated from cells in the suprafacial nucleus. Consistent with earlier observations with intramuscular HRP injections, the motoneuronal population devoted to vibrissal movement did not seem to be substantially larger than that for other facial movements.

An additional examination was made of the labelled afferent component of the facial motor nerve. We confirmed and extended previous findings that none of the above facial motor nerve branches, except the posterior auricular branch, contained a significant number of afferent fibers originating from the geniculate ganglion, the sensory ganglion of the seventh nerve. In addition, no labelling was seen in the mesencephalic trigeminal nucleus or trigeminal ganglion. These findings, in combination, suggest that, with the exception of the posterior auricular branch, all the facial motor nerve branches, including those involved in vibrissal movement, are almost entirely efferent.
The spinothalamic system of the rat. I. Locations of cells of origin
Authors: Granum Sherry L.
Published: January 2005

Horseradish peroxidase retrograde transport has been used to locate neurons of the rat spinal cord and lower medulla that project to the thalamus. Eight groups of spinothalamic cells are identified, some of which are anatomically continuous with thalamically projecting groups in the lower medulla. Most of the groups are seen only at the highest cervical levels, and several of them have not been previously recognised as spinothalamic relays. They are marginal layer (M), ventral border of the substantia gelatinosa (SGv), neck of the dorsal horn (Nl), lateral cervical nucleus (LCN), ventromedial portion of the dorsal horn (DHvm), intermediate gray zone (IGZ), dorsal portion of the ventral horn (VHd), and ventral portion of the ventral horn (VHv). Most of the cell bodies are contralateral to their thalamic terminations; only the VHd group is ipsilateral.

The major finding conflicts with traditional concepts of the spinothalamic system, and concerns the rostrocaudal distribution of the cells of origin. With the sole exception of the DHvm group, the great majority of the thalamically projecting neurons of the rat are confined to the most rostral spinal levels (medulla/cord junction through C4). Below C4, most of the spinothalamic cells are concentrated in a single DHvm group between levels T9 and L4, probably concerned with hindlimb proprioception.

The spinothalamic groups at high cervical levels may be relays for information ascending from lower regions. This might help to explain why, in man, surgical destruction of fibres crossing the midline in a single high cervical segment can cause a loss of pain sensation over most of the body.
Immunohistochemical distribution of substance P, serotonin, and methionine enkephalin in sexually dimorphic nuclei of the rat lumbar spinal cord
Authors: Micevych Paul E. , Coquelin Arthur , Arnold Arthur P.
Published: January 2005

The purpose of the present study was to identify chemically some potential inputs to lumbar motoneurons of the rat in the spinal nucleus of the bulbocavernosus, ventral motor pool, dorsolateral nucleus, and retrodorsolateral nucleus. Substance P‐like immunoreactivity and serotonin‐like immunoreactivity were found in all four motor nuclei, with dense immunoreactive profiles surrounding motoneurons and their processes. Enkephalin‐like immunoreactivity was restricted to the sexually dimorphic nuclei, the spinal nucleus of the bulbocavernosus, and the dorsolateral nucleus. Within the spinal nucleus of the bulbocavernosus, enkephalin‐like immunoreactive profiles were apposed to the processes of motoneurons but not their somata. In contrast, enkephalin‐like immunoreactivity surrounded motoneuron somata in the medial part but not the lateral part of the dorsolateral nucleus, in the location of motoneurons projecting to the ischiocavernosus muscle. Moreover, the density of serotonin‐like immunoreactivity was also greater in the medial part of the dorsolateral nucleus. On the basis of the chemo‐architecture and the connections of the dorsolateral nucleus, we suggest the division of this motor column into a medial part composed of ischiocavernosus motoneurons surrounded by enkephalin‐ and serotonin‐like immunoreactivity and a lateral part that contains neurons that project to the sphincter urethrae muscle.

Total spinal transection severely depleted both serotonin‐like and substance P‐like material in the lumbar ventral horn. No changes in the distribution of enkephalin‐like immunoreactivity were observed following this lesion. It is therefore suggested that in the ventral horn, substance P‐ and serotonin‐like material are derived from supraspinal tracts, whereas enkephalin‐like material is derived from intrinsic nerve cell bodies of the spinal cord.
A horseradish peroxidase study of the rubral and cortical afferents to the lateral reticular nucleus in the rat
Authors: Shokunbi M. T. , Hrycyshyn A. W. , Flumerfelt B. A.
Published: January 2005

The origin and organization of supraspinal afferents to the lateral reticular nucleus (LRN) in the rat were studied by means of the retrograde axonal transport of horseradish peroxidase (HRP). HRP was deposited into the LRN via both dorsal (stereotaxic) and ventral (microsurgical) routes. The entire cerebrum, brainstem, and cerebellum were surveyed for retrogradely labelled neurons. Significant projections arose from the contralateral red nucleus and the contralateral frontoparietal cortex.

The rubral projection arose from neurons in the caudal two‐thirds of the red nucleus. Ventrally and ventrolaterally located neurons projected to rostrolateral LRN, while dorsal and dorsomedial neurons projected to rostromedial LRN. The projection from the cerebral cortex arose from neurons located in layer V of the frontoparietal region. Rubral and cerebrocortical projections overlap in the rostral LRN, making this region of the nucleus a site of integration of descending inputs with ascending spinal signals.
The distribution of tyrosine hydroxylase, dopamine‐β‐hydroxylase, and phenylethanolamine‐N‐methyltransferase immunoreactive neurons in the feline medulla oblongata
Authors: Reiner Peter B. , Vincent Steven R.
Published: January 2005

The distributions and morphological characteristics of neurons displaying immunoreactivity to the catecholamine synthetic enzymes tyrosine hydroxylase (TH), dopamine‐β‐hydroxylase (DBH), and phenylethanolamine‐N‐methyltransferase (PNMT) were examined in adjacent sections of the feline medulla oblongata. TH‐positive neurons were found in two bilaterally symmetrical columns in the ventrolateral and dorsomedial medulla. Within the ventrolateral medulla, TH‐positive neurons were found within the lateral reticular formation throughout the entire rostrocaudal extent of the medulla. In the dorsomedial medulla, TH‐immunoreactive perikarya were localized to the nucleus of the tractus solitarius including the commissural subnucleus, the dorsal motor nucleus of the vagus, and the area postrema. DBH‐positive neurons had distributions and morphologies similar to those of the TH‐immunoreactive cells with three exceptions: TH‐positive neurons far outnumbered DBH‐positive neurons in the area postrema; slightly greater numbers of TH‐positive neurons were seen in the commissural nucleus of the tractus solitarius; and, caudal to the obex, only TH‐positive neurons were seen within the dorsal motor nucleus of the vagus.

PNMT‐immunoreactive neurons were found in all the nuclear regions of the medulla where both TH‐ and DBH‐positive neurons were seen. However, the PNMT immunoreactive perikarya had a somewhat more restricted distribution along the rostrocaudal axis. In the ventrolateral medulla, PNMT‐positive cells extended rostrally only as far as the retrofacial nucleus and caudally only to the obex. Within the dorsomedial medulla, PNMT immunoreactive cells were found from just rostral to the area postrema to the medullary‐spinal cord junction. These findings demonstrate that the distributions of TH, DBH, and PNMT immunoreactive perikarya in the medulla of the cat are generally similar to those seen in the rat insofar as these neurons are arranged in longitudinal columns in both species. However, significant differences exist with regard to the cytoarchitectonic borders within which immunoreactive perikarya can be found and the rostrocaudal extent of the PNMT‐positive cell groups in these two species.