bluuebunny/crossref_metadata_2025 huggingface dataset:
Light microscopic golgi study of mitral/tufted cells in the accessory olfactory bulb of the adult rat
Authors: Takami Shigeru , Graziadei Pasquale P. C.
Published: January 2005

Mitral/tufted cells (MTCs) of the accessory olfactory bulb (AOB) of adult rats were investigated light microscopically with the rapid Golgi method. The somata of the MTCs, appearing ovoid or triangular in shape, are distributed throughout the external plexiform layer. The soma size varies from small to large (12–26 μm). Apical dendrites originating from the soma enter the glomerular layer to provide branches that form the glomerular arbors. After making a glomerular arbor, some dendrites develop a second arbor (en passant and terminal arbors, respectively). The MTCs have a very diverse dendritic branching pattern and most have a variable number of glomerular arbors per cell (up to 6); we have tentatively classified the MTCs into simple, intermediate, and complex. Of the glomerular arbors, 80% have a diameter of less than 50 μm. The glomerular arbors have been classified as baskets (small spherical or ovoid) with short loopy processes; balls of yarn (large and nearly spherical) with loosely intermingled thick loops; and bushes (small to large and rather polymorphic) with irregular processes. The MTCs send dendritic arbors to terminate in one or more glomeruli where they are arranged in several different types of endings. Since it is generally believed that the dendrites of mitral and tufted cells of the main olfactory bulb terminate in only one glomerulus, the difference in the termination of the dendrites of the MTCs may represent a morphological characteristic that is relevant to the coding and/or integration of sensory information.
Appearance of somatostatin and vasoactive intestinal peptide along the developing chicken gut
Authors: Epstein Miles L. , Poulsen Kristian T.
Published: January 2005

The appearance of somatostatin (SOM)‐immunoreactive (IR) and vasoactive intestinal peptide (VIP)‐IR neurons in different regions of the embryonic chicken gut was studied by immunostaining wholemounts. The patterns of expression of these peptides in myenteric neurons showed a number of similarities. Both peptides first appeared in the region of the proventriculus‐gizzard: SOM at embryonic day (E)4, VIP at E5.5. At later times both peptides were found in positions both rostral and caudal to the gizzard. Both peptides appeared independently in cells at a second site, the cecum of the hindgut: SOM was observed at E6.5 and VIP at E7.5. VIP‐IR and SOM‐IR cells appear throughout the cecum, then in the rectum, and finally in the ileum. Differences in the patterns of expression were also found. SOM‐ and VIP‐IR neurons appeared at different times along the length of the gut. VIP‐IR cells populated the entire gut by E11.5, whereas SOM‐IR cells were not present throughout the gut until E13.5. SOM‐IR cells appeared in the terminal part of the ganglion of Remak at E4.0. At E6 these SOM‐IR cells sent fibers into the wall of the hindgut and later into the midgut. No VIP‐IR cells were found in the ganglion of Remak. These findings suggest that neural crest‐derived cells first express SOM‐ and VIP‐IR in particular regions of the gut, namely, the proventriculus‐gizzard and the cecum. Certain conditions must exist at these sites which favor the expression of these neuropeptides by neural crest‐derived cells. The observation of SOM‐ and VIP‐IR cells in the cecum at a stage of development before cells are seen in the ileum supports the concept that sacral neural crest cells contribute precursors for enteric neurons of the avian hindgut.
Sensory innervation of the rat kidney and ureter as revealed by the anterograde transport of wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP) from dorsal root ganglia
Authors: Marfurt Carl F. , Echtenkamp Stephen F.
Published: January 2005

The sensory innervation of the rat kidney and ureter was investigated in wholemount preparations and sectioned materials by labeling the afferent nerve fibers with wheat germ agglutinin Northwest Center for Medical Education, Indiana University School of Medicine, Gary, Indiana 46408horseradish peroxidase (WGANorthwest Center for Medical Education, Indiana University School of Medicine, Gary, Indiana 46408HRP) transported anterogradely from dorsal root ganglia. Labeled fibers were seen in large numbers in the ureter and in the lining of the renal pelvis, where they were located in the adventitia, smooth muscle, subepithelial connective tissue, and epithelium. Most of the fibers in the ureter and ureteropelvic junctional zone traveled parallel to the long axis of the organ. In contrast, fibers in the widest part of the funnel Northwest Center for Medical Education, Indiana University School of Medicine, Gary, Indiana 46408shape renal pelvis were oriented predominantly in a circumferential fashion. Many of the pelvic afferents were extremely fine and appeared to terminate as free nerve endings. Modest networks of labeled axons were also observed around branches of the renal artery; the greatest innervation was supplied to the distal portions of the interlobar arteries and to the arcuate arteries. Only single axons were observed around the interlobular arteries, and very few fibers were seen around afferent arterioles or near glomeruli. In contrast to the arteries, branches of the renal vein were relatively sparsely innervated. Occasional labeled fibers entered the renal cortex and formed intimate associations with renal tubules; however, the vast majority of renal tubular elements were not contacted by labeled sensory fibers. Labeled fibers were never observed in the renal medulla or in the papilla. The present study represents the first time that the sensory innervation of the kidney and ureter has been investigated by using a highly specific anterograde nerve tracing technique. The pattern of innervation demonstrated here reveals an anatomical configuration of ureteral and renal pelvic sensory nerves consistent with a role in detection of ureteral and pelvic pressure and chemical changes and a renal vascular sensory innervation that may monitor changes in renal arterial and venous pressure and chemical content. Still other renal afferent nerve endings may signal renal pain.
Effects of undernutrition during early life on granule cell numbers in the rat dentate gyrus
Authors: Bedi K. S.
Published: January 2005

Undernutrition during early life is known to affect the morphology of the hippocampal formation. Recent advances in stereological techniques have made it possible to make relatively unbiased estimates of total cell numbers in well‐defined brain regions. It was decided to use these methods to determine the effects of different levels of undernutrition during early postnatal life on the granule cells of the rat dentate gyrus.

Male hooded Long Evans rats were undernourished between the 16th day of gestation and 30 postnatal days of age to two different levels. The daily food intake of level‐1 and level‐2 rats represented about 60 and 40%, respectively, of that eaten by well‐fed, age‐matched controls. Nutritional rehabilitation of the rats was commenced when they had reached 30 days of age by placing them on an ad libitum diet. Groups of control and experimental rats were killed at 70 and 212 days of age. The Cavalieri principle was used to determine the granule cell layer volume within the dentate gyrus, and the “disector” method was used to determine numerical densities of these granule cells. These estimates were used to calculate the total numbers of granule cells.

There were between 260,000 and 320,000 granule cells within the dentate gyrus of 70‐day‐old control and experimental rats. By 212 days of age, well‐fed controls had an average of about 834,000 granule cells. The level‐1 and level‐2 previously undernourished rats had about 515,000 and 595,000 granule cells, respectively. Two‐way analysis of variance procedures showed significant main effects of nutrition and age as well as a significant interaction between them. These results provide strong evidence that a period of undernutrition during early life causes a long‐term deficit in the total number of dentate gyrus granule cells.
Serotoninergic innervation of the thalamus in the primate: An immunohistochemical study
Authors: Lavoie Brigitte , Parent André
Published: January 2005

Little is known of the serotoninergic innervation of the thalamus in primates; therefore, we undertook a detailed study of the distribution of 5‐hydroxytryptamine (5‐HT)‐immunoreactive neuronal profiles in the thalamus of the squirrel monkey (Saimiri sciureus) with a specific antibody directly raised against 5‐HT. All thalamic nuclei in the squirrel monkey displayed 5‐HT‐immunoreactive fibers, but none contained immunopositive cell bodies. The 5‐HT innervation of the thalamus derived from extrinsic fibers arising mostly from the midbrain raphe nuclei and forming the transtegmental system. Most of the fibers destined to the thalamus collected into a major bundle that swept dorsoventrally within the midbrain tegmentum and coursed beneath the thalamus along its entire caudorostral extent. Several fiber fascicles broke off from this main bundle at different levels and ascended dorsally to innervate the various thalamic nuclei. Overall, the 5‐HT innervation of the thalamus in the squirrel monkey was more massive than would have been expected from earlier studies in nonprimate species. Marked differences in the regional density of innervation were noted both between the various nuclei and within single nuclei. The most densely innervated nuclei were those delineating the principal subdivisions of the thalamic mass, that is, the midline, rostral intralaminar, limitans, and reticular nuclei, where very dense fields of isolated axonal varicosities occurred. In contrast to the rostral intralaminar nuclei, which were rather uniformly innervated, the centre médian/parafascicular complex contained immunoreactive fibers and isolated varicosities distributed according to a mediolateral gradient. The habenula and the ventral anterior nucleus were among the most weakly innervated nuclei. In the latter nucleus, as well as in more densely innervated nuclei, thin varicose fibers formed numerous pericellular contacts on cell bodies and proximal dendrites of thalamic neurons. The 5‐HT innervation of the lateral nuclear group as well as that of the medial and lateral geniculate nuclei ranged from very weak to dense. The mediodorsal nucleus displayed a highly heterogeneous 5‐HT innervation that varied from weak in its central portion to moderate or dense in its medial and lateral borders. A moderate 5‐HT innervation was observed in the anterior nuclear group. The surprisingly dense and heterogeneous 5‐HT innervation of the thalamus noted in the present study suggests that serotonin may be involved in several specific functions of the thalamus in primates.
Topography and ultrastructure of sensory nerve endings in the glans penis of the rat
Authors: Johnson Richard D. , Halata Zdenek
Published: January 2005

The aim of the present study was to describe the types and location of sensory nerve endings in the glans penis of the rat on the basis of light and electron microscopy. Free nerve endings are abundant throughout the glans and are derived from either thinly myelinated Aδ or unmyelinated C fibers. The free nerve endings derived from Aδ fibers often extend into the epidermis as far as the granular layer and exhibit buttonlike terminal thickenings. The distal urethra contains many free nerve endings from C fibers. Numerous lamellated corpuscles are present. Each corpuscle, innervated by one or two medium diameter myelinated nerve fibers, consists of 4–10 spiralling and intertwined inner cores enveloped by Schwann cell lamellae. The corpuscles are usually enclosed by a perineural capsule, although some located near the epidermis lack a capsule. Lamellated corpuscles in the superficial dermis are located adjacent to but not directly under a penile spine and change their orientation when the glans is erect. The dermal papillae of the penile spines are devoid of any neural structure. Lamellated corpuscles are also located within the trabeculae of the corpus spongiosum glandis and in the lamina propria of the urethra. Occasionally, unmyelinated nerve bundles are seen inside these corpuscles. Ruffini corpuscles are few in number and are located in the deep connective tissue near the os penis. They have an incomplete connective tissue capsule and the nerve terminals are anchored between collagen fiber bundles. No Merkel nerve endings, Meissner, or Vater‐Pacini corpuscles were found in any of the sections. We conclude that the glans penis of the rat contains a sensory receptor complement that is generally similar to the human glans penis but is unlike the glabrous and hairy skin.
Funicular organization of avian brainstem‐spinal projections
Authors: Webster D. M. S. , Steeves J. D.
Published: January 2005

The purpose of this study was to determine which reticulospinal projections need to be preserved to allow voluntary walking and to differentiate between those pathways descending within the ventrolateral funiculus versus the ventromedial funiculus. Retrogradely transported tracers (True Blue, Fast Blue, Diamidino Yellow dihydrochloride, fluoroscein‐conjugated dextran‐amines) were used alone as discrete funicular injections (4–5 μl) into the lumbar cord (L1), or in conjunction with a more rostral subtotal lesion of the low thoracic cord, to determine the trajectories of brainstem‐spinal projections in adult ducks and geese. No difference was found between the species. The major components of the ventromedial funiculus include projections from the medullary reticular formation, pontine reticular formation, raphe obscurus and pallidus, lateral vestibular nucleus, and interstitial nucleus, and to a minor extent from the locus coeruleus, lateral hypothalamus, and nucleus periventricularis hypothalami. The components of the ventrolateral funiculus (VLF) include projections from the nucleus of the solitary tract, nucleus alatus, pontomedullary reticular formation, raphe pallidus, raphe magnus, locus coeruleus, subcoeruleus, lateral vestibular, and descending vestibular nuclei. The principal descending projections within the dorsolateral funiculus (DLF) arose from the red nucleus, the paraventricular nucleus, locus coeruleus, subcoeruleus, dorsal division of the caudal medullary reticular formation, and raphe magnus. The functional implications of the distribution of these descending pathways are discussed with regard to locomotion. Since birds were able to walk despite bilateral lesion of the DLF or VMF but were unable to walk following a bilateral lesion of the VLF, this suggests that medullary reticulospinal pathways coursing within the VLF are essential for the provision of locomotor drive.
Prefrontal projections to the mediodorsal nucleus of the thalamus in the rhesus monkey
Authors: Siwek Donald F. , Pandya Deepak N.
Published: January 2005

The corticothalamic projections to the prefrontal cortex have been shown to be topographically organized. However, the underlying basis for this topography as it relates to the organization of the different architectonically defined areas of the prefrontal cortex has not been systematically studied. In the present investigation we have reassessed the thalamic projections from the different architectonic areas of the prefrontal cortex by using the technique of autoradiography in the rhesus monkey. The results show that the prefrontomediodorsal projections are organized according to the architectonic differentiation of the prefrontal cortices. Thus architectonically less differentiated medial and orbital prefrontal regions project to the medial sector of the mediodorsal nucleus, the magnocellular subdivision. In contrast, highly differentiated prefrontal area 8 projects to the most lateral sector of the mediodorsal nucleus, the multiformis subdivision. Lateral prefrontal areas with intermediate architectonic features project to the central parvocellular sector of the mediodorsal nucleus. Additionally, these projections also reveal a dorsoventral topography. Thus areas in the medial and dorsolateral cortices project to the dorsal part of the mediodorsal nucleus. In contrast, areas in orbital and ventrolateral cortices project to the ventral part of the mediodorsal nucleus.

The topographic organization of the corticothalamic connections described in this study corresponds to the progressive elaboration and differentiation of the architectonic features of the different prefrontal areas. This successive and dichotomous organization of prefrontothalamic connections may provide the basis for the observed differential functions of the prefrontal cortex and the mediodorsal nucleus.
Post‐rolandic cortical projections of the superior temporal sulcus in the rhesus monkey
Authors: Seltzer Benjamin , Pandya Deepak N.
Published: January 2005

The efferent connections of different cytoarchitectonic areas of the superior temporal sulcus (STS) in the rhesus monkey with parieto‐temporo‐occipital cortex were investigated using autoradiographic methods. Four rostral‐to‐caudal subdivisions of cortex (area TPO) in the upper bank of the STS have distinct projection patterns. Rostral sectors (areas TPO‐1 and ‐2) project to the rostral superior temporal gyrus (areas Ts1, Ts2, and Ts3), insula of the Sylvian fissure, and parahippocampal gyrus (perirhinal and prorhinal cortexes, areas TF, TH, and TL); caudal sectors (TPO‐3 and ‐4) project to the caudal superior temporal gyrus (areas paAlt and Tpt), supratemporal plane (area paAc), circular sulcus of the Sylvian fissure (area reIt), as well as medial paralimbic (areas 23, 24, and retrosplenial cortex) and extrastriate (areas 18 and 19) cortexes. Area TPO‐1 does not project to the parietal lobe; area TPO‐2 projects to the inferior parietal lobule; area TPO‐3 to the lower bank of the intraparietal sulcus (IPS) (area POa); and area TPO‐4 to medial parietal cortex (area PGm).

Vision‐related cortex (area TEa) in the rostral lower bank of the STS sends fibers to the rostral inferotemporal region (areas TE1, ‐2, and ‐3) and parahippocampal gyrus (perirhinal cortex, areas TF and TL). Visual zones in the caudal lower bank and depth of the sulcus (area OAa, or MT and FST) project to the caudal inferotemporal region (areas TE3 and TEO), lateral preoccipital region (areaV4), and lower bank of the IPS (area POa). A zone in the rostral depth of the STS (area IPa) projects to the rostral inferotemporal region, parahippocampal gyrus, insula of the Sylvian fissure, parietal operculum, and lower rim of the IPS (area PG).

STS projections to parieto‐temporo‐occipital cortex have “feedforward,” “feedbackward,” and “side‐to‐side” laminar patterns of termination similar to those of other cortical sensory systems. The differential connectivity supports the cytoarchitectonic parcellation of the STS and suggests functional heterogeneity.
Olivary morphology and olivocerebellar topography in adult lurcher mutant mice
Authors: Heckroth John A. , Eisenman Leonard M.
Published: January 2005

In adult lurcher mice, in which virtually all cerebellar Purkinje cells have degenerated as a direct consequence of mutant gene action, the inferior olivary complex suffers a severe retrograde transneuronal atrophy. Our analysis indicates a 63% cell loss in the lurcher inferior olive, homogeneously distributed between the medial and dorsal accessory, and principal olivary subdivisions. Olivary neurons are reduced in cross‐sectional area by 30% in lurcher mice, compared to normal controls. All olivary subdivisions morphologically identifiable in normal mice are also found in the lurcher inferior olive. Analysis of olivocerebellar topography by retrograde transport of lectin‐conjugated horseradish peroxidase and fluorogold, in both single and double labeling paradigms, reveals no abnormalities in the general organization of this highly ordered projection. This stability may be based on the initial establishment of the topographic pattern in late embryogenesis or early postnatal periods, prior to the onset of lurcher Purkinje cell degeneration, or, alternatively, the lurcher gene may not alter critical afferent and target characteristics at stages when the topographic relationship is being established. Once established, the olivocerebellar projection is apparently not dependent on the Purkinje cell for long‐term maintenance of its general topographic organization.
Evidence for new growth and regeneration of cut axons in developmental plasticity of the rubrospinal tract in the north american opossum
Authors: Xu Xiao M. , Martin George F.
Published: January 2005

We have shown previously that rubral axons can grow around a lesion of their spinal pathway in the developing opossum and that a critical period exists for that plasticity (Martin and Xu, Dev Brain Res 39:303, 1988). Since most rubrospinal neurons degenerate after axotomy during the critical period, we have proposed that plasticity results primarily from growth of late arriving axons around the lesion rather than regeneration of cut axons (Xu and Martin, J Comp Neurol 279:368, 1989). In the present study, we used a double‐labeling paradigm to test that hypothesis.

Four groups of pouch young opossums received bilateral or unilateral injections of Fast Blue (FB) into the caudal thoracic or rostral lumbar cord (T12–L2) at different ages in order to label rubrospinal neurons. Three or 4 days later, the rubrospinal tract was transected unilaterally, four to five segments rostral to the injection(s). If the injection was unilateral, the lesion was made ipsilateral to it. The animals were maintained for about 1 month before a second marker, Diamidino Yellow (DY), was injected, usually bilaterally, between the FB injection(s) and the lesion. The animals were maintained for about 5 days before sacrifice and sections through the red nucleus and spinal cord were examined with a fluorescence microscope.

During the critical period for plasticity, only a few rubral neurons contralateral to the lesion were labeled by FB alone, supporting our previous contention that most axotomized neurons degenerate. In contrast, many neurons were labeled by DY alone, indicating that their axons were not present in the caudal cord at the time of the FB injection and that they grew around the lesion during the 1 month survival to incorporate DY. A few double‐labeled neurons were also found. One interpretation of such neurons is that they survived axotomy, as evidenced by the presence of FB, and supported axons which grew around the lesion to take up DY. Another interpretation is that they supported late growing axons which incorporated residual FB as well as DY. In order to choose between these alternatives, a similar double‐labeling paradigm was carried out, but with removal of FB at the time of the lesion. Since a few neurons were still double labeled, we conclude that regeneration of cut axons also contributed to rubrospinal plasticity.

Our results support our previous suggestion that developmental plasticity of the rubrospinal tract results primarily from growth of late arriving axons around the lesion, but they also suggest that regeneration of cut axons occurs.
Calcitonin gene‐related peptide and corneal innervation: A developmental study in the rat
Authors: Jones Mark A. , Marfurt Carl F.
Published: January 2005

The development of calcitonin gene‐related peptide‐like immunoreactive (CGRP‐LI) nerves was studied in neonatal and adult rat corneas stained immunohistochemically according to an avidin biotin peroxidase procedure. At birth, rat corneas already contained dense plexuses of CGRP‐LI nerve fibers. Most of the nerves entered the cornea in 12–15 prominent stromal nerve bundles located at regular intervals around the circumference of the cornea. Fibers in these bundles entered the epithelium approximately midway between the limbus and the center of the cornea and supplied extensive central and pericentral areas of the tissue. In addition, smaller numbers of axons entered the cornea individually and in small fascicles located in between the larger bundles and supplied mainly peripheral territory. In the epithelium, the CGRP‐LI nerves formed a complex, highly anastomotic meshwork that ramified uniformly throughout central and peripheral areas of the tissue. Fibers in the plexus gave origin to numerous short, stout terminal axons that extended into the adjacent epithelium in all directions with no preferred orientation. During the first week of neonatal life, several changes in CGRP‐LI innervation occurred: (1) the innervation density of the central and pericentral cornea increased relative to the peripheral cornea; (2) intraepithelial axons became progressively longer, increased in branching complexity, and oriented preferentially towards the center of the cornea; and (3) a dense innervation of the corneoscleral limbus and, in particular, the branches of the marginal artery, developed. Midway through the second week of life, immature versions of Corneal epithelial “leashes,” the dominant feature of the adult corneal innervation, were first observed. Over the next 10 days, the leash formations in the central and pericentral cornea gradually became more complex and gave rise to greater numbers of terminal axons, compared to developing leashes in the peripheral cornea. The mature pattern of corneal CGRP‐LI innervation was reached on day 21 and remained constant (except for compensatory growth‐related elongation of axons) for at least the first 6 months of life. Transection of the ophthalmomaxillary nerve or neonatal administration of the sensory neurotoxin capsaicin resulted in the total loss of CGRP‐LI staining from the cornea. In contrast, removal of the superior cervical ganglion had no effect on corneal CGRP‐LI staining. The extraordinary density and complexity of the CGRP‐LI innervation of the rat cornea demonstrated at all stages of development in this study suggests that these nerves may play important roles in corneal sensory, reflex, and trophic functions.
Structure of the macroglia of the retina: Sharing and division of labour between astrocytes and Müller cells
Authors: Holländer Horstmar , Makarov Felix , Dreher Zofia , van Driel Diana , Chan‐Ling Tailoi , Stone Jonathan
Published: January 2005

A detailed comparison is made between astrocytes and Müller cells of the cat's retina, with emphasis on their structural specialisations. Evidence is presented that astrocytes and Müller cells both contribute to the formation of the inner glia limitans of the retina, the glia limitans of vessels, and the glial sheaths of neurones. In particular, it was noted that both astrocytes and Müller cells wrap bundles of ganglion cells axons, that both contribute processes to the glial convergence on the initial segments and node‐like structures of axons, and that both wrap the somas of neurones in the ganglion cell layer. Further, it was noted that adherent junctions form between astrocytes, between Müller cells, and between astrocytes and Müller cells, but not between these cells and neurones, or among neurones. These similarities suggest that astrocytes and Müller cells function interchangeably in many respects, and we suggest that they be regarded as variants of macroglia.

Quantitative differences between astrocytes and Müller cells were noted in their ensheathment of neurones. In particular, the glial sheaths around the somas of ganglion cells are formed predominantly by Müller cells, and the glial processes attached to node‐like specialisations of their axons are formed mainly by astrocytes. One qualitative difference was noted between the two cell classes. The gap junctions which form between astrocytes do not form between Müller cells or between cells of the two classes. From these differences, and previously established features of their shape, orientation, distribution and origin, a hypothesis is developed of the specialisation of macroglia represented by Müller cells.
Prenatal descent of rubrospinal fibers through the spinal cord of the rat
Authors: Lakke E. A. J. F. , Marani E.
Published: January 2005

This study is the first description of the descent of rubrospinal fibers through the spinal cord of the rat fetus. Either horseradish peroxidase or wheat germ agglutinin‐horseradish peroxidase conjugate was injected into the spinal cord, at different levels and at different gestational ages. At embryonic day 17 (E17) fibers from all subdivisions of the nucleus ruber (NR) started their descent towards the spinal cord. At E18 fibers from the ventrolateral NR reached the lower cervical spinal cord, and those from the caudal NR reached the lower thoracic spinal cord. At E19 fibers from the dorsomedial NR and from the parvicellular NR had just reached the cervical spinal cord, while fibers from the ventrolateral and caudal NR descended to lower thoracic levels. At E21 fibers from the dorsomedial NR reached the lower cervical spinal cord. Fibers from the ventrolateral and caudal NR completed their descent through the lumbosacral spinal cord during the first three postnatal days. During their descent the rubrospinal fibers were confined to the white matter of the spinal cord.

The earliest descending fibers originated in the caudal NR. Fibers from the caudal part of each magnocellular subdivision of the NR descended before their rostral counterparts. Fibers from the dorsomedial NR only reached the cervical enlargement as the fibers from the ventrolateral NR descended through the cervical enlargement. The somatotopy of the adult rubrospinal projection reflects this sequence; the dorsomedial NR (dmNR) projects to the cervical spinal cord, and the ventrolateral NR (vlNR) projects to the lumbosacral spinal cord. In general, early descending fibers originated from neurons located caudally and ventrolaterally, while later descending fibers originated from neurons located progressively more rostrally and dorsomedially in the magnocellular NR.
Thalamic processing of vibrissal information in the rat. I. Afferent input to the medial ventral posterior and posterior nuclei
Authors: Chiaia Nicolas L. , Rhoades Robert W. , Bennett‐Clarke Carol A. , Fish Stephen E. , Killackey Herbert P.
Published: January 2005

Retrograde tracing with true blue (TB) and diamidino yellow (DY) and anterograde tracing with either wheatgerm agglutinin–conjugated horseradish peroxidase (WGA‐HRP) or Phaseolus vulgaris leucoagglutinin (PHA‐L) were employed to investigate the projections from trigeminal nucleus principalis (PrV) and trigeminal subnucleus interpolaris (SpI) to their targets in the medial ventral posterior (VPM) and posterior (POm) nuclei of the thalamus. Many more cells in both PrV and SpI were labeled by tracer injections into VPM than into POm. Only a very small number of double‐labeled neurons were observed in either PrV or SpI. However, a significantly higher percentage of SpI cells projected to POm or to both POm and VPM than was the case for PrV. Anterograde tracing with WGA‐HRP showed that the projections from both PrV and SpI to VPM were much denser than those from the same nuclei to POm. Small injections of PHA‐L into either PrV or SpI produced a focus of fairly dense labeling in VPM and much more diffuse terminal labeling in POm. These anatomical data provide evidence for two separate trigeminothalamic pathways, one originating from PrV and the second originating from SpI. Both of these pathways converge and diverge at the thalamic level. That is, information from the PrV pathway and from the SpI pathway are both provided to VPM in a morphologically restricted fashion and to POm in a morphologically widespread fashion.
Serotoninergic innervation of the ferret cerebral cortex. II. Postnatal development
Authors: Voigt Thomas , de Lima Ana Dolabela
Published: January 2005

We have investigated the serotoninergic innervation of the ferret cortex from the day of birth to adulthood with immunohistochemical techniques. Due to the premature birth of ferrets, this period spans the entire generation of cells located within the upper cortical layers and their subsequent migration to their final positions. Already at birth, serotoninergic fibers innervate the developing cortex. This innervation is most dense within the marginal zone, the subplate region, and the lower portion of the cortical plate. As long as cell migration continues, serotoninergic fibers enter the expanding portions of the cortex. Only the region just below the marginal zone where newly arriving cells are added to the cortical plate is not innervated by the ingrowing fibers. When the bulk of cell migration ceases, during the third postnatal week, this gap disappears and the fibers gradually form a continuous innervation from the pia to the ventricle. As the cortex matures, the serotoninergic fibers become successively confined to the upper layers, to generate the adult pattern. In the adult ferret cortex, the highest innervation density is found within layers 1, 2, and 3, with a much sparser innervation within the lower layers (Voigt and de Lima, J. Comp. Neurol. 314:403–414, 1991). The dense innervation in the deep cortical layers is only transient, virtually disappearing toward adulthood. These results suggest that serotoninergic axons innervate cortical layers as soon as newly arriving cells reach their final positions within the cortex. This early innervation lends support to the idea that serotonin may play a role during development of the cerebral cortex.
The distribution of neurotransmitters and neurotransmitter‐related enzymes in the dorsomedial telencephalon of the pigeon (Columba livia)
Authors: Krebs John R. , Erichsen Jonathan T. , Bingman Verner P.
Published: January 2005

Immunoreactivity to four neurotransmitters/transmitter‐related enzymes was found in the dorsomedial telencephalon (hippocampal region) of the pigeon. Putative afferent fibers containing choline acetyltransferase‐like, serotonin‐like, and tyrosine hydroxylase‐like immunoreactivity were seen in a fiber tract passing through the septo‐hippocampal junction and along the medial wall of the hippocampal region. The most intensive labeling of neuropil and terminals of all four substances was found in the dorsomedial area of the hippocampal region. Glutamic acid decarboxylase‐like immunoreactivity was seen in sparsely scattered cells throughout the region. These results are discussed in relation to hypotheses about the boundaries and subdivisions of the hippocampal region of the pigeon.
Thalamic projections to the lateral suprasylvian visual area in cats with neonatal or adult visual cortex damage
Authors: Kalil Ronald E. , Tong Lillian , Spear Peter D.
Published: January 2005

Previous transneuronal anterograde tracing studies have shown that the retino‐thalamic pathway to the posteromedial lateral suprasylvian (PMLS) visual area of cortex is heavier than normal in adult cats that received neonatal damage to visual cortical areas 17, 18, and 19. In contrast, the strength of this projection does not appear to differ from that in normal animals in cats that experienced visual cortex damage as adults. In the present study, we used retrograde tracing methods to identify the thalamic cells that project to the PMLS cortex in adult cats that had received a lesion of visual cortex during infancy or adulthood. In five kittens, a unilateral visual cortex lesion was made on the day of birth, and horseradish peroxidase (HRP) was injected into the PMLS cortex of both hemispheres when the animals were 10.5 to 13 months old. For comparison, HRP was injected bilaterally into the PMLS cortex of three cats 6.5 to 13.5 months after they received a similar unilateral visual cortex lesion as adults. In cats with a neonatal lesion, retrograde labeling was found in the large neurons that survive in the otherwise degenerated layers A and A1 of the lateral geniculate nucleus (LGN) ipsilateral to the lesion. Retrograde labeling of A‐layer neurons was not seen in the undamaged hemisphere of these animals or in either hemisphere of animals that had received a lesion as adults. As in normal adult cats, retrograde labeling also was present in the C layers of the LGN, the medial interlaminar nucleus, the posterior nucleus of Rioch, the lateral posterior nucleus, and the pulvinar nucleus ipsilateral to a neonatal or adult lesion. Quantitative estimates indicate that the number of labeled cells is much larger than normal in the C layers of the LGN ipsilateral to a neonatal visual cortex lesion. Thus the results indicate that the heavier than normal projection from the thalamus to PMLS cortex that exists in adult cats after neonatal visual cortex damage arises, at least in part, from surviving LGN neurons in the A and C layers of the LGN. Although several thalamic nuclei, as well as the C layers of the LGN, continue to project to PMLS cortex after an adult visual cortex lesion, these projections appear not to be affected significantly by the lesion.
An immunocytochemical analysis of the lateral geniculate complex in the pigeon (Columba livia)
Authors: Güntürkün Onur , Karten Harvey J.
Published: January 2005

The lateral geniculate complex (GL) of pigeons was investigated with respect to its immunohistochemical characteristics, retinal afferents, and the putative transmitters/modulators of its neurons. The distributions of serotonin‐, choline acetyltransferase‐, glutamic acid decarboxylase‐, tyrosine hydroxylase‐, neuropeptide Y‐ (NPY), substance P‐ (SP), neurotensin‐ (NT), cholecystokinin‐ (CCK), and leucine‐enkephalin‐ (L‐ENK) like immunoreactive perikarya and fibers were mapped. Retinal projections were studied following injections of Rhodamine‐B‐isothiocyanate into the vitreous. Transmitter‐specific projections onto the visual Wulst and the optic tectum were studied by simultaneous double‐labelling of retrograde tracer molecules and immunocytochemical labelling.

The GL can be divided into three major subdivisions, the n. geniculatus lateralis, pars dorsalis (GLd; previously designated as the n. opticus principalis thalami, OPT), the n. marginalis tractus optici (nMOT), and the n. geniculatus lateralis, pars ventralis (GLv). All three subdivisions are retinorecipient. The GLd can be further subdivided into at least five components differing in their immunohistochemical characteristics: n. lateralis anterior (LA); n. dorsolateralis anterior thalami, pars lateralis (DLL), n. dorsolateralis anterior thalami, pars magnocellularis (DLAmc); n. lateralis dorsalis nuclei optici principalis thalami (LdOPT); and n. suprarotundus (SpRt). The LdOPT consists of an area of dense CCK‐like and NT‐like terminals of probable retinal origin. Three subnuclei (DLL, DLAmc, SpRt) were shown to project to the visual Wulst. Cholinergic and cholecystokinergic relay neurons participated in this projection.

The nMOT occupies a position between the GLd and GLv and encircles the rostral pole of n. rotundus and the LA. It is characterized mainly by medium sized NPY‐like perikarya which were shown to project onto the ipsilateral optic tectum. Bands of NPY‐like fibers in the tectal layers 2, 4, and 7 could at least in part be due to this projection of the nMOT. Most of the antisera used revealed transmitter/modulator‐specific fiber systems in the GLv which often showed a layer‐specific distribution. Perikaryal labelling was only obtained with glutamic acid decarboxylase.

On the basis of its chemoarchitectonics, topography, and connectional pattern, the GLd complex of pigeons is most directly equivalent to the mammalian GLd. However, although the different subdivisions of the avian GLd may represent functionally different channels within the thalamofugal pathway similar to the lamina‐specific differentiation within the mammalian geniculostriate projection, direct comparison of subnuclei of birds and mammals is not justified at this time. The nMOT appears similar to the intergeniculate leaflet (IGL) and the avian GLv clearly corresponds in many features to the mammalian GLv.
Light and electron microscope study of GABA‐immunoreactive neurones in Lamina III of rat spinal cord
Authors: Powell James J. , Todd Andrew J.
Published: January 2005

In order to determine whether different morphological types of neurone in lamina III of rat spinal dorsal horn contain different neurotransmitters, a combined Golgi and immunocytochemical study was performed. Semithin sections through the cell bodies of 52 Golgi‐impregnated neurones in this lamina were tested with antisera to GABA and glycine. Thirty of these cells were immunoreactive with anti‐GABA antiserum and 25 of these also showed glycine‐like immunoreactivity. These cells had dendrites which were oriented along the rostrocaudal axis and occupied lamina III, with some extension into lamina IV and the ventral half of lamina II. Although some of the nonimmunoreactive cells had similar morphology, many of them had dendrites which passed in a dorsal and/or ventral direction and crossed laminar boundaries. Three of the neurones which were immunoreactive with both antisera were examined with the electron microscope. These cells received a variety of synapses including some from axons which resembled low threshold myelinated mechanoreceptive primary afferents.

These results indicate that there is a relationship between morphology and function for neurones in lamina III. It is suggested that the inhibitory neurones which contain both GABA and glycine selectively regulate the transmission of information from low threshold mechanoreceptive primary afferents to other dorsal horn neurones.
Vibrissectomy induced changes in GAP‐43 immunoreactivity in the adult rat barrel cortex
Authors: Dunn‐Meynell A. A. , Benowitz L. I. , Levin B. E.
Published: January 2005

Within the rat primary somatosensory cortex, neurons responding principally to movement of each individual mystacial vibrissa are grouped together in structures termed barrels. Previous studies have examined changes in the area of cortex showing increased 2‐deoxyglucose uptake in response to vibrissal stimulation. These studies have shown that chronic removal of all but the central (C3) vibrissa in adult rats induces an enlarged representation of the remaining C3 barrel in the contralateral cortex. This increase is prevented by cortical norepinephrine depletion. The major question raised by such studies is whether such plasticity is due to structural rearrangement or unmasking of otherwise silent synapses. In this study, antibodies to GAP‐43, a presynaptic protein whose synthesis is related to neuronal development and regeneration, were used to investigate this issue. In adult rat brain, tangential sections through layer IV of the barrel receptor field normally show moderate levels of GAP‐43 immunoreactivity (GAP‐IR) in the inter‐barrel septa and low levels within the barrels themselves. The present study examined changes in the pattern of GAP‐IR from 1 to 8 weeks after vibrissectomy with sparing of C3 as an index of possible physical reorganization of cortical circuits. Quantitative analysis of the cortices of animals with unilateral vibrissectomy with sparing of C3 showed that the area of low GAP‐IR within the barrels surrounding C3 was decreased at 1 week (8.4% shrinkage; P < 0.01) and 8 weeks (12.0% shrinkage; P < 0.015), relative to the cortex ipsilateral to the surgery. Both bilateral vibrissectomy with sparing of C3 and ibotenic acid lesions of the ventrobasal thalamus produced similar results. Some evidence was also seen that the area of low GAP‐IR in the C3 barrel shrank to a similar degree after such manipulations. Cortical norepinephrine depletion had no apparent effect on vibrissectomy‐induced GAP‐IR changes. These results suggest that removal of vibrissal input to the adult rat barrel cortex produces transynaptic induction of axonal sprouting within the barrel cortex.
Normal development and effects of deafferentation on the morphology of superior collicular neurons projecting to the lateral posterior nucleus in hamster
Authors: Mooney Richard D. , Savage Steven V. , Hobler Scott , King Tod D. , Rhoades Robert W.
Published: January 2005

Visually responsive neurons in the superficial layers of the hamster's superior colliculus (SC) can be divided into distinct morphological and functional classes. In the preceding paper (Mooney et al., '91), we showed that neonatal enucleation has only slight and insignificant effects upon the structural characteristics of cells within a given class, but results in a significant reduction of neurons (narrow and widefield vertical cells) with dorsally directed dendritic arbors. In an effort to determine whether this change reflected differential transneuronal degeneration of these cell types or alterations in the dendritic arbors of surviving cells, this study re‐examined this issue by restricting the analysis to a specific and relatively homogeneous subpopulation of superficial layer neurons, those that project to the lateral posterior nucleus (LP). Physiological recordings demonstrated that most (64.7%) tecto‐LP cells in neonatally enucleated hamsters develop somatosensory receptive fields. The combination of retrograde tracing and injection of cells with Lucifer yellow in a fixed slice preparation demonstrated that nearly 75% of tecto‐LP cells in normal adult hamsters are widefield vertical cells while less than 25% of the neurons filled in neonatally enucleated adults are in this class. Most of the tecto‐LP cells in the neonatally enucleated adult hamsters were either horizontal cells (19.5%), giant stellate cells (24.6%), or had dendrites that were directed only toward the deep SC laminae (10.3%). Differential enucleation‐induced cell death could not account for all of these changes. Tecto‐LP neurons were retrogradely labelled with the carbocyanine dye, Di‐I, in hamsters on postnatal day (P‐) 0 (the day of birth) through P‐10. As early as P‐0, most retrogradely labelled neurons could be identified as either widefield (44.6%) or narrowfield (18.9%) vertical cells. These results, when considered together with those from the normal adult and neonatally enucleated adult hamsters, support the conclusion that neonatal eye removal results in a reorganization of the dendritic arbors of some collicular neurons that have already undergone considerable development at the time of the lesion.
Substance P innervation of the rat and cat thalamus. I. Distribution and relation to ascending spinal pathways
Authors: Battaglia Giorgio , Spreafico Roberto , Rustioni Aldo
Published: January 2005

An antiserum for substance P (SP) with minimal cross‐reactivity for other tachykinins was employed to map the distribution of SP‐positive nerve fibers and terminals in the thalamus of cats and rats with special emphasis on the innervation by these fibers of nuclei related to the somatosensory system. In both species SP innervation is predominantly along the midline, in medial and posterior thalamic regions, and sparser in sensory relays for specific modalities. Among the most densely innervated nuclei are the parafascicular, paraventricular, rhomboid, central medial and parts of mediodorsal, lateral posterior, and ventral lateral geniculate. SP innervation of somatosensory‐related nuclei is also evident in central lateral nucleus, posterior complex (PO), and in ventroposterolateral (VPL) nucleus of both cats and rats. In VPL of cats SP fibers and terminals are present along its ventral and lateral border, a paralaminar area in which spinothalamic fibers have been shown to terminate and where neurons responsive to noxious stimuli have been reported. Also in rats the SP innervation of VPL is similar to that of spinothalamic tract fibers. The SP innervation of somatosensory thalamic nuclei may be supplied, at least in part, by spinothalamic afferent as suggested by the depletion of SP after anterolateral chordotomy but not after ablation of the dorsal column nuclei. The presence of SP‐positive spinothalamic neurons in the spinal cord is reported in the following paper.