bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of GABA‐T‐Intensive neurons in the hat forebrain and midbrain
Authors: Nagai T. , McGeer P. L. , McGeer E. G.
Published: January 2005

The neuronal distribution of 7‐aminobutyric acid (GABA) transaminase (GABA‐T), the enzyne which metabolizes GABA, has been mapped in rat brain. The method involves staining for newly synthesized GABA‐T by the previously established nitro blue tetrazolium technique in animals killed 8–48 hours after administration of gabaculine, an irreversible inhibitor of GABA‐T. Neuronal staining is obscured by staining of other elements if initial suppression is inadequate or survival times postgabaculine are too long. With appropriate conditions, GABA‐T‐positive neuronal somata can be widely detected. The stained cells include neuronal groups previously reported to be GAB Aergic on the basis of glutamate decarboxylase (GAD)‐col‐chicine immunocytochemistry and other methods, i.e.: Purkinje, basket, Golgi, and stellate neurons of the cerebellum; basket and stellate neurons of the hippocampus; granule and periglomerular cells of the olfactory bulb; magnocellular neurons of the hypothalamus; and neurons of the striatum, pallidum, entopeduncular nucleus, cortex, medial septal area, diagonal band, substantia innominata, reticular nucleus of the thalamus, substantia nigra, and dorsal raphe. Other cells that stain intensely for GABA‐T and may be GABAergic include neurons in the midlateral septal area, accumbens, the central medial and basal. nucler of the amyugdala, zona in certa, the brainstem reticular formation, central gray, interstitial nucleus of Cajal, and various thalamic nuclei including the periventricular, intralami‐nar, rhomboid, and subparafascicular. Known non‐GABA neuronal groups are negative for GABA‐T staining under these conditions, reinforcing the hypothesis that GABA neurons are far more GABA‐T intensive than other neurons.
The secondary olfactory connections in two chondrichthians, the shark Scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J.
Published: January 2005

The secondary olfactory connections in the shark Scyliorhinus canicula and the ray Raja clavata have been studied with reduced silver techniques. After transction through the pedunculus olfactorus in Scyliorhinus degenerating fibers could be traced to the telencephalic hemisphere. On entering the henisphere these fibres subdivide into a small medial and a larger lateral olfactory tract. The medical olfactory tract also projects contralaterally to the submeningeal pallial zone via the commissural olfactoria inferior and to the stratum granulare bulbi olfactorii by way of the commissural olfactoria superio. The lateral olfactory tract distrubytes mainly to the pallium laterale. A striking difference between Scyliorhibnus and Raja is that in the latter no contralaterature for other cartilaginous fishes, it appears that the secondary olfactory connections of Sycliorhinus are more extensive than in other chondrichthians studied experimentally.

In some cases of peduncle transction in Scyliorhinus the lateral part of the sttiatum was also involved in the lesion. In addition to the pattern of degeneration seen after olfactory peduncle lesions, degenerating fibres could be distinguished both in the stria medullaris and basal forebrain bundle. The former projects to hebenular nucleus, whereas the latter distributes to the hypothalamus, and brainstem tegmentum.
Thalamocortical projections in the reeler mutant mouse
Authors: Caviness Verne S. , Frost Douglas O.
Published: January 2005

The normal radial distribution of the different neocortical cell classes is inverted in the reeler mutant mouse. The organization of the thalamocortical projection in adult reelers has been investigated by using anterograde degeneration techniques. Thalarnocortical mons follow anomalous trajectories to their target cytoarchitectonic fields in the mutant. After leaving the internal capsule, the axons ascend in sigmoid‐shaped fascicles to enter a fiber stratum near the cortical surface. The axons course through this superficial stratum until they reach their target fields and then descend to terminate in deeper cortical planes. In the normal animal, by contrast, the mons course tangentially at the interface of the cortex with the subcortical white matter; upon reaching their target fields, they ascend to terminate more superficially in the cortex. Thus, in both genotypes the tangential portions of the axon trajectories pass through the polymorphic cell population.

Both with respect to degree of divergence and the radial distribution of terminals within the different cytoarchitectonic fields, the thalamocortical projection in reeler, like that in the normal animal, appears to be composed of two distinct axon classes. The “class I” axons, the less‐divergent system which terminates densely in two or three tiers within the cortex, are the subject of the present analysis. The “class 1” projections form an orderly cortical representation of the thalamus: Despite distortions in the topography of the reeler thalamus and cortex, both the nucleus to field relationships and the detailed topologic organization of the projection appear to be normal.

The terminals of class I projections are distributed in radially segregated tiers that resemble the tiered pattern of termination as in normal mice, and there are field‐specific variations in the tiers that, like those of normal mice, are systematically related to variations of cortical cytoarchitecture. Thus, similar mechanisms, which may depend in part on the interaction of ingrowing axons with specific postsynaptic cell surfaces, must determine the restricted radial distribution of thalamocortical projections in both genotypes. However, there is an abnormal mix of somata and dendrites at all radial levels of the mutant cortex, suggesting that the spatial domain of termination of thalamocortical axons may be governed to some extent by factors other than the distribution of specific prospective postsynaptic cell surfaces.

The reeler mutation alters the radial but not the tangential structure of the neocortex, suggesting that these two aspects of cortical organization develop under the control of independent mechanisms. The present results suggest that despite the anomalies of radial position, normal relationships between thalamocortical afferents and distinct classes of postsynaptic elements with characteristic radial distributions are largely conserved in reeler. Certain types of aberrant connections are highly probable, however.
Plasticity of the corticospinal tract following midthoracic spinal injury in the postnatal rat
Authors: Bernstein Deborah R. , Stelzner Dennis J.
Published: January 2005

Rats received a midthoracic spinal cord “overhemisection” including right hemicord and left dorsal funiculus at birth (neonatal operates, N = 15) or 21 days of age (weanling operates, N = 14). In a second experiment neonatal (N = 6), 6‐day (N = 3), and 12‐day (N = 7) rats sustained a right sensorimotor cortex (SmI) ablation to destroy the left corticospinal tract (CST) at the same time as the spinal injury (double lesion operates). Later (3–12 months) injections of 3H‐proline and autoradiography were used to label the left or right CST. The results of the first experiment showed that most right CST axons failed to grow around the spinal lesion in neonatal operates (N = 9). There was an increase in the density of label, mainly to CST projection areas, in a 1‐mm zone rostral to the lesion. However, left CST axons bypassed the lesion by growing through the intact tissue in neonatal operates (N = 6). These displaced axons were consistently located within the dorsal portion of the lateral funiculus (dLF) and remained within that location caudal to the lesion, an area normally containing only a few CST axons. In spite of this abnormal position, these axons terminated bilaterally throughout the remainder of the cord in normal CST sites. In weanling operates, CST axons severed by the lesion did not regenerate around the lesion site. An increased density of label over the few spared axons within the left dLF and in CST projection zones immediately caudal to the lesion site suggested axonal sprouting by these axons. The results of the second experiment showed that the lack of growth of right CST axons around this injury in neonatal operates was, at least partially, due to an interaction with left CST axons. In neonatal double lesion operates, right CST axons grew around the spinal injury for a varying distance within the left dLF and distributed bilaterally to normal CST sites. The number of right CST axons bypassing the lesion was related to the configuration of the lesion site. A smaller number of right CST axons bypassed the lesion in 6‐day double lesion operates and most terminated within 2–3 mm of the lesion site. Right CST axons failed to grow around this injury in 12‐day double lesion operates. We conclude that the availability of intact spinal cord tissue allows uncut developing left CST axons to grow around a lesion when their primary pathway is destroyed. Differences in growth of left and right CST axons appear to be related to an interaction between left and right CST axons which limits the growth of right CST axons across the midline. The ability for CST axons to grow around this injury decreases at the time these axons are elongating through this region and ceases at the time synapses are being formed by these axons. However, further experiments are necessary to determine if these factors in the maturation of the CST, of if other factor in the maturation of the spinal cord, are critical in limiting CST groth after spinal injuryin the developing CNS.
Hyperplasia in the spinal sensory system of the frog. I. Plasticity in the most caudal dorsal root ganglion
Authors: Davis Miriam R. , Constantine‐Paton Martha
Published: January 2005

Increases in the amount of periphery available for innervation have been achieved by the unilateral removal of hindlimb dorsal root ganglion (DRGs) in Rana pipiens, a procedure which generally results in a compensatory cell number increase (hyperplasia) in the DRGs which remain. We have found that the hyperplastic response is extremely variable, and we have investigated various factors which might control its production. Our findings indicate, however, that the pattern of DRGs removed, the animal's age at the time of removal, and the survival period are not strictly related to the production of hyperplasia in hindlimb DRGs.

Special emphasis has been placed on DRG 10, the caudalmost DRG which normally innervates the cloaca and sends a small projection to the hindlimb. This DRG displayed dramatic cell number increases of up to 564%. In addition, several unique features of the hyperplastic response have been observed in DRG 10. This DRG showed increases in cell number on both the operated and the unoperated sides. It showed hyperplasias in animals subjected to gangh'onectomy past metamorphosis as well as during larval development. Finally the production of DRG 10 hyperplasias exclusively occurred in male pre‐and postrnetamorphic animals. To account for these distinctive features of DRG 10 hyperplasia, baseline studies of the normal course of proliferation and cell death in DRG 10 were undertaken. They reveal no fundamental developmental differences between DRG 10 and other hindlimb DRGs. Other mechanisms responsible for these unusual features of developmental plasticity in DRG 10 are discussed.
Hyperplasia in the spinal sensory system of the frog. II. Central and peripheral connectivity patterns
Authors: Davis Miriam R. , Constantine‐Paton Martha
Published: January 2005

Central and peripheral connectivity patterns of hyperplastic dorsal root ganglia (DRGs) in Rana pipiens are examined in order to determine the relative roles of peripheral and central contacts in the production of DRG hyperplasias. The hyperplasias are produced in the intact hindlimb DRGs after the removal in tadpoles and young postmetamorphic frogs of neighboring DRGs (Davis and Const an tine‐Paton, '83). The peripheral target zones of the hyperplastic DRGs, determined by physiological recordings of sensory receptive fields, are found to undergo a significant degree of expansion relative to controls. Peripheral expansion is most pronounced in caudalmost DRG 10, and this effect occurs in experimental animals operated during larval and postmetamorphic stages. Further, anatomical labelling of peripheral sensory fibers coursing to the hindlimb reveals that the hyperplastic DRG 10 actually contains additional fibers projecting to the denervated regions. The central projection of the hyperplastic DRG 10 does not show corresponding increases in longitudinal arborization after the application of horseradish peroxidase to the appropriate dorsal roots. These observations are made on some of the same experimental animals in which peripheral fields are shown to have vastly expanded. We conclude that the peripheral processes of the hyperplastic DRGs are less rigidly specified than the central terminations, and that it is the periphery which plays the primary role in controlling the cell numbers increases.

A second aim of this investigation is to identify whether sexually dimorphic connectivity patterns in normal frogs explain the production of DRG 10 hyperplasias exclusively in male experimental animals (Davis and Constantine‐Paton, '83). We apply the same techniques used in our connectivity studies of hyperplastic DRGs to the investigation of connectivity patterns of DRG 10s in normal males and females. No sex‐dependent differences in peripheral and central connectivity are found. Thus, since normal male and female frogs possess an equivalent amount of target space for DRG 10, the unique production of hyperplasias in male experimental animals cannot be explained solely on the basis of connectivity. We speculate on what other factors may be involved.
Topography of spinal, dorsal column nuclear, and spinal trigeminal projections to the pontine gray in rats
Authors: Swenson Rand S. , Kosinski Ross J. , Castro Anthony J.
Published: January 2005

Several studies using a variety of animals have reported conflicting evidence concerning the distribution, laterality, and indeed the presence of ascending projections to the pontine nuclei. In an attempt to clarify this issue, projections to the pontine nuclei from the spinal cord, dorsal column nuclei, and spinal trigeminal nucleus were investigated with anterograde methods, i.e., the Fink‐Heimer technique and/or autoradiography, in Long‐Evans black‐hooded rats. Results revealed that dorsal column nuclear projections to the contralateral pontine gray terminate predominantly in two regions – one in the caudal aspect of the medial pontine subdivision and another overlapping the ventral and lateral subdivisions. Within the medial and ventrallateral nuclear regions, fibers from nucleus cuneatus primarily terminated more rostrally to afferents from the nucleus gracilis. Spinal trigeminal projections terminated most heavily within the contralateral pontine gray at midpontine levels. Similar to the dorsal column nuclear projections, trigeminal afferents were observed in the medial and ventrolateral subdivisions, although these terminations were rostral and dorsal to areas receiving cuneatus input. Additional projections from the spinal trigeminal nuclei to the contralateral ventral peduncular nucleus were also observed. In comparison to the above‐mentioned pontine afferents, both high cervical and midthoracic spinal cord lesions produced a similar pattern of axonal degeneration in the ipsilateral pontine gray which overlapped substantially with gracilis inputs. The observed topographic distribution pattern of ascending afferents to pontine gray confirm and extend previous findings which in general have only briefly described these pathways.
Light and electron microscopic studies of the basilar papilla in the duck, Anas platyrhynchos. II. Embryonic development
Authors: Chandler John P.
Published: January 2005

The intent of this study was to describe certain morphological aspects of cytodifferentiation of the basilar papilla in the duck, Anas platyrhynchos. The duck, with a longer incubation period than that of the chicken, has proven useful in identifying the earliest morphological changes during cytodifferentiation of the basilar papilla. Most of these changes occur first at the neural margin of the presumptive genu, at the site of initial contact by cochlear nerve fibers. A wave of differentiation of hair cells radiates abneurally, proximally, and distally, concurrent with the establishment of afferent innervation. Extracellular channels form in the papilla between cell bases just before the nerve fibers penetrate the basal lamina. Nerve fibers abut hair cell bases in the genu at the time the hair cells separate from the basal lamina on day 9. Hair cell bases contain granular vesicles and lie among the nuclei of supporting cells on day 10. Synaptic bodies are present opposite nerve endings on day 11. Efferent nerve endings appear on short hair cells in the genu on day 15 and on tall hair cells on day 17.
Synaptology of retinal terminals in the dorsal lateral geniculate nucleus of the cat
Authors: Rapisardi Salvatore C. , Miles Toni P.
Published: January 2005

We have made a fine structural investigation of the synaptic patterns made by axon terminals of retinal ganglion cells in the dorsal lateral geniculate nucleus of the cat. We compared the retinal input to dendritic processes that bear clusters of large appendages with the retinal input to relatively smooth dendritic segments that have only a few isolated spines. The study was restricted to the portion of laminae A and A1 that receive central visual field input. We were able to completely reconstruct 33 individual terminal boutons from long series of consecutive thin sections. Retinal terminals that were presynaptic to dendritic appendages tended to occupy the central position in the complex synaptic zones of geniculate fine structure called glomeruli. These terminals were surrounded by significantly more profiles than retinal terminals that were presynaptic to dendritic stems and averaged twice as many synaptic contacts per terminal bouton. The retinal input to dendritic appendages was heavily involved in a specific synaptic pattern called the triadic arrangement while retinal input to dendritic stems was only lightly involved in triads. Dendritic appendages in triads received greater synaptic input from profiles with flattened vesicles than did the dendritic stems that were found in triads.
An atlas of the primary visual projections in the brain of the chick Gallus gallus
Authors: Ehrlich David , Mark Richard
Published: January 2005

The localisation of the primary visual centres in the chick mesencephalon and diencephalon was determined by autoradiographic anterograde transport and degeneration techniques. Strong visual projections were found in the tectum, lateral anterior thalamic nucleus, lateroventral geniculate nucleus, superficial synencephalic nucleus, external nucleus, ectomammillary nucleus, tectal grey, dorsolateral anterior thalamus, rostrolateral part, and the pretectal optic area. Weaker retinal projections were found in the ventrolateral thalamus, two subregions of the dorsolateral anterior thalamus, lateral part, diffuse pretectal nucleus, dorsolateral anterior thalamus, magnocellular part, and the hypothalamus. An atlas of the retinal projections was constructed from sections.
An immunocytochemical study of the serotonergic innervation of the thalamus of the rat
Authors: Cropper E. C. , Eisenman J. S. , Azmitia E. C.
Published: January 2005

The serotonergic innervation of the rat thalamus was studied with an indirect immunocytochemical technique using an antiserum raised against a serotonin‐hemocyanin conjugate in animals pretreated with L‐tryptophan and a monoamine oxidase (MAO) inhibitor. When pretreatment was not used there was a decrease in the number of immunoreactive fibers observed in the thalamic region.

Innervation was greatest in nucleus ventralis corporis geniculati lateralis, and in the following midline nuclei: nucleus periventricularis, nucleus rhomboideus, and nucleus reuniens. Also well labeled were nucleus anterior ventralis, the intralaminar nuclei, and nucleus lateralis dorsalis. Moderate innervation was found in nucleus reticularis, nucleus anterior dorsalis, nucleus ventralis medialis, nucleus lateralis pars posterior, the posterior complex, and in nucleus dorsalis corporis geniculati lateralis. Very few serotonergic fibers were observed in nucleus paratenialis, nucleus gelatinosus, nucleus anterior medialis, nucleus medialis dorsalis, nucleus ventralis, nucleus ventralis pars dorsomedialis, or in nucleus corporis geniculati medialis. Serotonin immunoreactivity was also noted in a number of fiber bundles in the thalamic region. These include the fasciculus retroflexus, the fasciculus mamillothalamicus, the stria medullaris, and the stria terminalis.

These results differ from those of previous descriptions of the serotonergic innervation of thalamic nuclei most notably in the midline nuclei and in the posterior complex. In this study the midline nuclei, nucleus rhomboideus, and nucleus reuniens were more densely innervated than had been described, and in the posterior complex a moderate, rather than sparse, innervation was observed. The more densely innervated nuclei of the anterior and lateral nuclear groups, nucleus lateralis dorsalis and nucleus anterior ventralis, also contained a greater number of labeled fibers than had been indicated.
Distribution of immunoreactive substance P neurons in the hypothalamus and pituitary of the rhesus monkey
Authors: Rønnekleiv Oline K. , Kelly Martin J. , Eskay Robert L.
Published: January 2005

The distribution of immunoreactive substance P (IR‐SP) neurons was examined in the hypothalamus and pituitary gland of the rhesus monkey by using the peroxidase‐antiperoxidase immunocytochemical technique. Immunoreactive SP cell bodies were observed in the arcuate nucleus, in the region lateral to the arcuate nucleus, and in the median eminence (ME). Immunoreactive SP cells were also seen in the periventricular area of the dorsal tuberal region. A rich network of SP fibers was concentrated in the arcuate region, and the fiber stain was particularly dense in the external zone of the median eminence and in the external layer of the infundibular stalk. Also, substance P fibers were seen in the internal layer of the pituitary stalk and in the neural lobe of the pituitary gland. Outside the hypothalamus a dense network of IR‐SP fibers was observed in the globus pallidus.
The development of retinal ganglion cells in a tetraploid strain of Xenopus laevis: A morphological study utilizing intracellular dye injection
Authors: Sakaguchi D. S. , Murphey R. K. , Hunt R. K. , Tompkins R.
Published: January 2005

The morphological development of retinal ganglion cells was examined in a tetraploid strain of Xenopus frogs. The enlarged cells of the tetraploid strain facilitate the application of intracellular techniques. Using an in vitro retinal preparation and Nomarski optics, intracellular recording and dye injection were carried out under visual control on ganglion cells in central retina from 2 days of development (stags 24) to metamorphosis (stage 64).

We identified three phases in the morphological differentiation of ganglion cells. During the first phase (stages 24–30), all cells were neuroepitheliallike in form and possessed robust resting potentials in the range of ‐35 to ‐60 mV, and dye‐coupling was occasionally observed between neighboring cells. During the second phase of ganglion cell development (stages 31–45) the neurons had begun to elaborate axons and dendrites. These cells possessing neurites had resting potentials between ‐15 and ‐30 mV, and no dye‐coupling was observed between neighbors. During the third and final phase of maturation, from stage 46 onward, three distinct morphological types of ganglion cells could be identified. Type I cells had the smallest somata and the smallest‐diameter dendritic arborizations. The profusely branched dendrites of these cells ramify extensively throughout the inner plexiform layer. Type II cells had large somata, intermediate‐diameter dendritic fields, and a highly elaborate dendritic branching pattern. These cells were seen to arborize within two sublamina in the inner plexiform layer. Type III cells had large somata, the largest‐diameter dendritic fields, and a dendritic arbor with long primary branches but little higher‐order branching. These large dendritic fields were confined to a single sublamina of the inner plexiform layer, abutting the inner nuclear layer. While most phase 3 cells showed radial axon trajectories from the soma to the optic disc, a minority of cells (1–5%) with erratic and nonradial axon trajectories were also observed.

Our data provide a morphological description of ganglion cell maturation in the central retina of Xenopus. We show that very early in development (as early as stage 46) three distinct morphological types of retinal ganglion cells are Present, which corresnond to the three classes of ganglion cells previously described in adult Xenopus (Chung et al., '75).
Ultrastructural correlates of electrical‐chemical synaptic transmission in goldfish cranial motor nuclei
Authors: Hackett J. T. , Buchheim A.
Published: January 2005

The output connections of the cranial relay neurons, part of the Mauthner cell network, were examined in goldfish with light and electron microscopic techniques. Either lueifer yellow or horseradish peroxidase (HRP) was injected into cranial relay neuron axons to demonstrate that they diverge to several motor nuclei and to many motoneurons within one nucleus. Retrograde transport of the enzyme from injections of mandibular muscles was used to label the trigeminal motoneurons.

In the electron microscope, cranial relay neuron processes were distinguished by the granular appearance of the electron‐opaque polymer formed enzymatically by HRP, while the retrogradely labeled motoneurons had the polymer enclosed in lysosomes. The cranial relay neuron terminals contained many presynaptic vesicles which concentrated the HRP reaction product. Active zones and synaptic clefts were evident. At some synapses, both gap junctions and presynaptic vesicles were found.

The mechanism of synaptic transmission was investigated by simultaneous recording with two intracellular microelectrodes from cranial relay neuron‐motoneuron pairs. Composite postsynaptic potentials in a trigeminal motoneuron were evoked by intracellular stimulation of a cranial relay neuron axon. The earliest excitatory postsynaptic potential (EPSP) component had a latency of 0.25 sec and had a peak amplitude that was not depressed by repetitive stimulation. A second component had larger peak amplitudes which were reduced easily by repetitive stimulation. Antidromic action potentials were not transmitted from motoneurons to the cranial relay neuron axons.

Thus, both electrical and chemical transmission probably occur at the cranial relay neuron‐motoneuron synapses. Since the cranial relay neurons fire synchronously and receive excitatory chemical synapses, the function of the gap junctions and electrical transmission is unclear. Perhaps the importance of these gap junctions is more for transport of small molecules than for impulse transmission.
Topographic organization of the olivocochlear projections from the lateral and medial zones of the superior olivary complex
Authors: Guinan John J. , Warr W. Bruce , Norris Barbara E.
Published: January 2005

By anterograde tracing using autoradiography, we have found topographic organizations in the projections of both medial and lateral olivocochlear (OC) systems in the cat. Lateral‐zone injections show an ipsilateral cochleotopic projection pattern with more medial injections projecting more basally in the cochlea. In the contralateral cochlea, in contrast, the projections from all of the lateral‐zone injections were predominantly to the apex. However, detailed analysis suggests the possibility that the contralateral lateral‐zone projections may have the same cochleotopic organization as the ipsilateral projections but with a heavy bias toward the apex. Medial‐zone injections show a pattern in which more dorsal regions project more basally in both cochleas. The ipsilateral projections of lateral OC neurons appear to connect regions with similar best frequencies but the projections of medial OC neurons do not. Summation of data from all of the injections in each zone indicates that lateral OC projections are relatively evenly distributed throughout the ipsilateral cochlea but are predominantly to the apex in the contralateral cochlea. Medial OC projections are predominantly to the middle and basal parts of the cochlea on both sides with contralateral projections somewhat more basal than ipsilateral projections.
The distribution of substance P in turtle nervous system: A radioimmunoassay and immunohistochemical study
Authors: Reiner Anton , Krause James E. , Keyser Kent T. , Eldred William D. , McKelvy Jeffrey F.
Published: January 2005

The distribution of a substance P‐like material in turtle brain, spinal cord, dorsal root ganglion, and retina was determined using radioimmunoassay (RIA) and immunohistochemistry. High levels of a substance P‐like material were found in turtle neural tissue, particularly in basal telencephalon, hypothalamus, and tegmentum. In many regions, the concentration of a substance P‐like material in turtle nervous tissue was found to be similar, in a region‐to‐region comparison, to that previously reported for birds and mammals, particularly for the more “phylogenetically conservative” parts of the nervous system (such as the basal ganglia, tegmentum, and hypothalamus). The slopes of substance P RIA dose‐response curves for tissue extracts from nearly all regions of the turtle nervous system examined were parallel to a standard dose‐response curve for synthetic substance P (SP). The immunohistochemical results, with anti‐substance P antisera from guinea pig or rabbit, or with a monoclonal antibody, were consistent with the RIA data. Regions showing high concentration of an SP‐like material by RIA were observed to contain numerous neurons and/or fibers containing an SP‐like material. The immunohistochemical results provide evidence for the presence in turtle of numerous SP‐containing pathways, several of which (e.g., an SP‐containing strionigral pathway, an SP‐containing striopallidal pathway and an SP‐containing dorsal root ganglia‐spinal dorsal horn pathway), have been described in birds and mammals. The present results thus suggest that the neuropeptide SP has had a largely stable evolutionary history as a transmitter or modulatory agent during amniote brain evolution.
Peptide‐like immunoreactivity in anuran optic nerve fibers
Authors: Kuljis Rodrigo O. , Krause James E. , Karten Harvey J.
Published: January 2005

Unilateral section, crush, or ligation of the optic nerve was performed in Rana pipiens. Following optic nerve disruption, Substance P (SP)‐, leucine‐enkephalin (LENK)‐, cholecystokinin octapeptide (CCK8)‐, and bombesin (BOM)‐like immunoreactivities were analyzed in the retinae and optic nerves. Peptide‐like immunoreactivity developed in the retinal stump of disrupted optic nerves within 1 hour after surgery and was retained until at least 30 days. Peptide‐positive staining in the retinal stump of the optic nerves was abolished by preabsorption of each of the antibodies/antisera with the corresponding synthetic substances. No massive peptide‐like immunoreactivity was observed in the cerebral stump of the ligated side, nor in the contralateral, nonoperated, optic nerve. No change in the pattern of peptide‐like immunoreactivity was apparent in the retina ipsilateral or contralateral to the experimental procedure. The optic tectum contralateral to the surgical procedure displayed those changes in peptide‐like immunoreactivity described previously following retinal deafferentation (Kuljis and Karten, '82a, '83a).

Peptide‐like immunoreactivity in the stump retinad to the surgical procedure occurred in the form of beaded and fibrillar elements often ending in an irregular expansion near the lesion site. Fluorescent double‐label antibody methods demonstrated that SP‐like immunoreactivity is present in different processes than those containing LENK, CCK8, or BOM. Electron microscopical immunocytochemistry revealed that peptide‐like immunoreactivity is contained within unmyelinated and possibly also within myelinated axons in the stump retinad to the traumatic procedure. Radioimmunoassay studies of SP demonstrated a four‐ to sixfold increase in SP‐like content in the retinal stump of ligated nerves, compared with both the cerebral stump and with the contralateral nonoperated optic nerves.

These findings demonstrate the presence of peptide‐like immunoreactivity in retinal ganglion cell processes, which is compatible with either a posttraumatic expression of previously repressed peptide‐like phenotypes, or, most likely, with the existence of various classes of peptide‐containing retinal ganglion cells. The latter prospect strongly suggests that peptide‐specific subsets of retinal ganglion cells terminate in highly specific laminae in the optic tectum (Kuljis and Karten, '81, '82a‐83a) and presumably differ in their physiological role in vision. Thus, these observations provide direct anatomo‐chemical evidence in support of Lettvin et al. ('59) and Maturana et al. ('60), regarding the differential laminar termination of physiologically diverse classes of retinal ganglion cells in the tectum.
The location and morphology of preganglionic neurons and the distribution of visceral afferents from the rat pelvic nerve: A horseradish peroxidase study
Authors: Nadelhaft Irving , Booth August M.
Published: January 2005

Preganglionic neurons of the sacral parasympathetic nucleus (SPN) were located almost exclusively (98%) within the L6‐S1 spinal cord segments. The SPN contained approximately 550 neurons of medium size (10 × 20 μm). These were mainly located in the intermediolateral gray matter and had dendrites that extended into the dorsolateral funiculus, along the lateral marginal zone of the dorsal horn, and medially into the dorsal gray commissure. Labeled dorsal root ganglion cells were almost all located (95%) in the L6 and S1 ganglia. An average of approximately 1,500 sensory neurons were found. These were small cells (17 × 25 μm) whose central processes entered Lissauer's tract from which two groups of collaterals emerged: 1) a prominent lateral pathway along the lateral margin of the dorsal horn that extended into the region of the SPN and also into the dorsal gray commissure, 2) a less prominent medial pathway extending around the dorsal margin of the dorsal horn to terminate in the dorsal gray commissure. These two collateral groups formed fiber bundles that were spaced by approximately 100 μm between centers when observed in the horizontal plane. A third afferent bundle, composed of rostrocaudally oriented fibers, was located in the sagittal plane immediately ventral to the central canal. Comparisons are made between the results in rats and the results of similar experiments performed in cats and monkeys.
Temporal and spatial constraints on the collateral sprouting of low‐threshold mechanosensory nerves in the skin of rats
Authors: Jackson Patrick C. , Diamond Jack
Published: January 2005

We have studied the collateral sprouting of intact low‐threshold mechanosensory nerves into adjacent denervated skin in rats. An “isolated” field was produced by extensive denervations of the surrounding skin; sprouting of the remaining cutaneous nerve supplying the field was looked for in the form of field expansion into the surrounding denervated territory at various postoperative intervals. Such isolated fields failed to expand in the adult rat for periods up to at least 85 days. “Nonfunctional” sprouting is unlikely to explain this failure. However, similar experiments done in very young animals gave a different result. In rat pups aged less than 20 days, isolated fields did expand, but this ceased at about 20 days, and attempts to evoke it after this time were unsuccessful. There seems to be a critical period for sprouting of these touch‐sensitive nerves into denervated skin, and our evidence suggests that it may not begin until about 15 days of age. Within this developmental window the sprouting that occurs is spatially constrained, an isolated field expanding preferentially into denervated skin of the parent dermatome; if only skin of neighboring dermatomes is available there is no expansion. In contrast, low‐threshold nerves regenerated readily after a crush at all ages studied, and the mechanosensory fields established by regenerating nerves expanded progressively into denervated skin without apparent constraints at dermatomal boundaries. The temporal and spatial constraints found for the sprouting of intact low‐threshold axons are in marked contrast to their absence for the well‐described sprouting of high‐threshold (nociceptive) nerves.
Relationships between the nigrotectal pathway and the cells of origin of the predorsal bundle
Authors: May Paul J. , Hall William C.
Published: January 2005

The goal of this study was to define the anatomical relationships between the terminal field of the nigrotectal pathway and the tectal neurons which project to contralateral brainstem gaze centers by way of the predorsal bundle. The distribution and morphology of the cells of origin for the predorsal bundle were determined by using a modification of the retrograde horseradish peroxidase technique which homogeneously filled their somas and dendrites. The terminal distribution of the nigrotectal tract was determined using both anterograde horseradish peroxidase and autoradiographic procedures.

The results indicate that, in the grey squirrel (Sciurus carolinensis), the predorsal bundle cells are a heterogeneous population whose dendritic fields form a well‐defined band confined to the inner half of stratum griseum intermediale. This inner sublamina also can be identified in Nissl and myelin stains. The same sublamina is the major target of the nigrotectal tract. The striking anatomical correspondence between the distribution of nigrotectal terminals and the cells projecting in the predorsal bundle supports a proposal, based on recent physiological investigations, that the nigrotectal tract plays an important role in the initiation of the saccade‐related activity of the deep tectal cells (Chevalier et al., '81; Hikosaka and Wurtz, '83a–d).
Neurotensin in the ventromedial mesencephalon of the rat: Anatomical and functional considerations
Authors: Kalivas Peter W.
Published: January 2005

Neurotensin is an endogenous neuropeptide that fulfills some of the criteria for a neurotransmitter in the mammalian central nervous system. It exists in high concentrations in the ventral tegmental area and adjacent midline nuclei of the ventromedial mesencephalon, and recent microinjection studies have demonstrated that neurotensin can act in this brain region to produce both a decrease in colonic temperature, and an increase in spontaneous motor activity. In this study it was found that hypothermia was most successfully evoked following neurotensin injection along the midline of the ventral mesencephalon, corresponding to the nucleus linearis centralis. In contrast, behavioral hyperactivity was produced with greatest consistency in the ventral tegmental area, corresponding to the nucleus paranigralis and nucleus parabrachialis pigmentosus. However, in its caudal aspect, the nucleus paranigralis was found unresponsive to neurotensin. Behavioral hyperactivity was also observed after neurotensin injection along the midline into the nucleus interfascicularis. Only injections made into the nucleus linearis rostralis produced hypothermia and hyperactivity in the same rat. This distribution of neurotensin‐responsive nuclei corresponded to the distribution of neurotensin containing perikarya and fibers. With the exception of the nucleus interfascicularis, neurotensin‐containing neurons were distributed throughout the rostral portion of the ventromedial mesencephalon, the nucleus parabraehialis pigmentosus containing the greatest density. However, in the caudal portion, neurotensin neurons were found almost exclusively in the nucleus linearis centralis. Neurotensin‐containing fibers were of greatest density in the nucleus interfascicularis and the nucleus linearis centralis. Considering the known capacity of neurotensin to activate dopamine neurons in the ventromedial mesencephalon, and the partial mediolateral topographical distribution of dopaminergic projections from this region to the limbic forebrain, it is possible that neurotensin may be activating two distinct populations of dopamine neurons to produce hypothermia and behavioral hyperactivity.
A Golgi analysis of the primate globus pallidus. II. Quantitative morphology and spatial orientation of dendritic arborizations
Authors: Yelnik Jérôme , Percheron Gérard , François Chantal
Published: January 2005

The morphology of pallidal neurons was analyzed quantitatively in Golgi‐impregnated brains of men and macaques (Macaca irus). Selected neurons were drawn with a camera lucida and reconstructed from serial sections. Dendritic arborizations were analyzed in three dimensions using a video computer microscope (Yelnik et al., 1981). Morphological (topological and metrical) parameters were computed, and the overall geometry of arborizations was studied in three dimensions with the aid of principal component analysis (Yelnik et al., 1983). Statistical tests were used in order to compare human with simian large neurons and the lateral with the medial pallidum. All neurons were found to belong to a single neuronal population. Particular neurites may be added randomly onto pallidal dendrites, mainly in the lateral pallidum. Large pallidal neurons are characterized by sparsely branched dendritic arborizations (4 stems, 13 tips) with thick, smooth, and long dendrites (longest dendrite = 1,000 μm, total dendritic length = 7,600 μm). All arborizations are discoidal in shape with mean dimensions of 1,500 × 1,000 × 250 μm. Pallidal discs are always parallel to the lateral border of each pallidal nucleus and thus perpendicular to striatal axons to which they present their greatest extent. They may be traversed by a large number of these axons. The existence of other pallidal neuronal groups, “intermediate” and “local circuit” neurons, identified in their fine morphological features by François et al. (1984), was confirmed quantitatively in the present study.
A Golgi analysis of the primate globus pallidus. III. Spatial organization of the striato‐pallidal complex
Authors: Percheron Gérard , Yelnik Jérôme , François Chantal
Published: January 2005

An atlas of transverse sections of the globus pallidus and striatum was established in macaque with reference to ventricular coordinates. The three‐dimensional geometry of the striato‐pallidal complex was investigated by means of sagittal and horizontal reconstructions. Both a personal case studied with autoradiography and data from literature were used to analyze the distribution of cortical axons into the striatum. One may distinguish two striatal territories: one, somatotopically arranged, sensorimotor territory extending over the major part of the putamen; and the other, an associative territory, comprising the caudate nucleus and antero‐medial and postero‐inferior parts of the putamen. The striato‐pallido‐nigral bundle was studied using Golgi, Perls, and Fink‐Heimer techniques. The bundle is described in four parts: prepallidal (subdivided into caudato‐pallidal and putamino‐pallidal subparts), transpallidal, pallido‐nigral, and nigral. The tracing of the limit between the caudate (associative) and putaminal (essentially sensorimotor) territories shows that the two components are of roughly the same size in the pallidum. The data were compared with geometry and orientation of the dendritic arborizatons of large pallidal neurons analyzed in Yelnik et al. (1984). Each pallidal dendritic disc is able to receive axons from a wide region of the striatum. This leads to a convergence on pallidal neurons of striatal axons from different striatal somatotopic strips and from the sensorimotor and associative territories. This is an indication that the globus pallidus may have an integrative role.
Immunoelectron‐microscopic study on the fine structure of substance‐P‐containing fibers in the taste buds of the rat
Authors: Yamasaki Hiroshi , Kubota Yoshiyuki , Takagi Hiroshi , Tohyama Masaya
Published: January 2005

The fine structure of substance‐P‐like immunoreactive [SPI] fibers in the taste buds of the circumvallate papillae of the rat tongue was investigated by means of electron microscopy using the unlabeled antibody‐enzyme method.

Outside the epithelium, SPI and non‐SPI fibers are surrounded by the cytoplasm of Schwann cells. When the SPI fibers enter the epithelium, they immediately lose this cytoplasmic sheath and begin to traverse the taste buds. Though passing through the taste buds, no profiles suggesting clear synaptic contact between SPI fibers and underlying cells are identified. SPI terminals are filled with small synaptic vesicles and contain a few mitochondria. No SPI‐positive structures are found in nerve endings that make synaptic contact with type III cells, the gustatory receptor cells.
Localizing spinal‐cord‐projecting neurons in adult albino rats
Authors: Leong Seng Kee , Shieh Jeng Yung , Wong Wai Chow
Published: January 2005

Following horseradish peroxidase injection into the cervical and lumbosacral cords of adult albino rats, labeled neurons were seen in the first cervical segment, brain stem, and cerebellar and diencephalic nuclei. A new pathway, the faciospinal projection, originating in the medial portion of the rostral part of the facial nucleus, was traced. Another new pathway, the olivospinal pathway, is probably also present. Our results for neurons projecting to the spinal cord (spinal‐projecting neurons) from the nucleus ambiuus, dorsal motor nucleus of the vagus, superior vestibular nucleus and nucleus f, nucelus Darshevch, nucleus Rolleri, nucleus prepositus hypoglossi, and nucleus of the posterior commissure have been reported before in other mammals but not in rats. Projections from the following regions are in general agreement with previous results in rats, but show significant topographical differences: the first cervical segment; nuclei gracilis, cuneatus, and cuneatus lateralis; the midline and lateral reticular nuclear complex; the trigeminal nuclear complex (spinal, principal, and mesencephalic); nucleus of the tractus solitarius; the medial, lateral, and descending vestibular nuclei, nuclei coeruleus and subcoeruleus; superior colliculus; interstitial nucleus of Cajal, and the deep cerebellar nuclei. The distribution of labeled neurons in the nucleus parabrachialis, nucleus tegmentolaterodorsalis, nucleus Kölliker‐Fuse, nucleus Edinger‐Westphal, and the hypothalamic nuclear complex confirmed that of previous reports in rats.

With the exception of a few nuclear groups which project primarily to either lumbosacral (e.g., the paraventricular nucleus of the hypothalamus) or cervical segments (e.g., the facial motor nucleus and the superior colliculus) most of the other nuclear groups project to both the lumbar and cervical levels. There is no distinct somatotopy in the neuronal groups projecting to both cervical and lumbosacral levels.

With only a few exceptions (e.g., the superior vestibular nucleus) most of the spinal‐projecting neurons are bilaterally distributed, some with contralateral and others with ipsilateral predominance.