bluuebunny/crossref_metadata_2025 huggingface dataset:
Time course and distribution of motoneuronal loss in the dorsal motor vagal nucleus of guinea pig after cervical vagotomy
Authors: Laiwand R. , Werman R. , Yarom Y.
Published: January 2005

Cells in the dorsal motor vagal nucleus (DMVN) of the adult guinea pig were counted at different times after unilateral cervical section of the vagus nerve. The counts were made from serial 30 μm coronal sections throughout the DMVN in normal and operated animals. There are three types of cells in the DMVN of guinea pig: medium‐sized motoneurons that are retrogradely filled by HRP from the site of the vagotomy, small neurons, and glial cells. An interesting observation was a change in distribution of cells in the DMVN with age in unoperated guinea pigs.

Following vagotomy degeneration was seen only in the motoneurons. Disappearance of motoneurons was slow and only 27% were present after 1 year. During that time the decrease in the total number of motoneurons was exponential with a time constant of 8.6 months, but degeneration in different parts of the nucleus was not uniform. Thirty‐four percent of motoneurons in the caudal area of DMVN disappeared in the first month after vagotomy, while the rostral area was almost unchanged. The rostral area, however, showed rapid degeneration between 3 and 6 months after vagotomy. The central part of the nucleus degenerated at a constant rate between those of the rostral and caudal regions. At the end of 1 year, cell loss in all parts of the nucleus was approximately equal.

Surviving motoneurons showed morphological changes: rounding of the soma, continuous reduction of the cell volume, and shrinkage of the nucleus. Occasional abnormal forms showing vacuolization or invaginated nuclei were seen. Calculations show that the process of degeneration lasts 25 days on the average.

The marked degeneration found in dorsal vagal motoneurons, in contrast to recovery from axotomy in somatic motoneurons, is similar to that found in intrinsic neurons of the central nervous system. The slow and continuous time course of disappearance of motoneurons after vagotomy, however, is exceptional. It is reasonable to postulate that the increased vulnerability of these motoneurons may be sufficient to result in degeneration in response to what are normally nonpathological metabolic demands.
Specific neurotrophic interactions between cortical and subcortical visual structures in developing rat: in vivo studies
Authors: Haun Forrest , Cunningham Timothy J.
Published: January 2005

The specificity of trophic interactions in the rat visual system is investigated in vivo by using a combination of tissue culture and CNS transplantation methods. In a companion paper (Repka and Cunningham: '87) we showed that explants of embryonic day 14 (E14) occipital cortex are biased to contain different cortical cell populations depending on whether the explants develop in culture with diencephalon or with optic tectum. In this study we transplanted these precultured cortical explants into the cavity created by a lesion of the occipital cortex in newborn rats and then measured the neuron‐occupied volume and the numbers of thymidine‐labeled cells in the surviving ipsilateral dorsal lateral geniculate nucleus (dLGN) of the host rats. The results were compared to (1) animals with lesions but no transplants, (2) animals with transplants of E14 cortical tissue that had not been precultured, and (3) animals with cerebellar transplants that had been similarly precultured either with other cerebellar tissue or with diencephalon. At 5 days postlesion, both the largest dLGN volume and the greatest number of labeled dLGN neurons survive in animals with cortical transplants precultured with diencephalon or other cortex. The surviving dLGN neurons that are rescued by these transplants are generated on E15 or E16, a period that corresponds to the latter part of geniculate neurogenesis. Relatively few cells generated on E14 survive in any group of animals. Furthermore, animals with all types of cortical transplants have significantly larger volumes of surviving dLGN than animals with either leisons only or cerebellar transplants. However, by 9 days postlesion, the dLGN has almost completely disappeared in all groups of rats, indicating that the effect of the transplants is temporary. The results demonstrate that cortical transplants can protect host neurons in particular stages of development from degeneration after a cortical lesion and suggest that a particular population of later‐generated cortical cells is responsible for this effect. Since many of these later‐generated cells may represent neurons that are the natural targets of dLGN neurons, the results suggest a high degree of neurotrophic specificity during in vivo development of the rat visual system.
Opposing parallel connections through crayfish local nonspiking interneurons
Authors: Nagayama T. , Hisada M.
Published: January 2005

Unilateral local nonspiking interneurons in the terminal (sixth) abdominal ganglion of crayfish (Procambarus clarkii Girard) can be classified into two major groups of PL and AL types by their gross morphology and somatic position. These premotor interneurons are the neural components of uropod motor pattern formation. They receive sensory input from the exopodite of the contralateral side as well as that of the ipsilateral side. Small fluctuations in their membrane potentials cause sustained change in activity of the motoneurons innervating the uropod muscles. PL interneurons, which make noninverting connections to an identified closer, the reductor motoneuron No. 1, mainly receive excitatory input from the afferents of the contralateral exopodite, whereas inverting PL interneurons receive inhibitory input. AL interneurons receive distinctly different input from the afferents. Noninverting AL interneurons mainly receive inhibitory input, whereas inverting AL interneurons receive excitatory input. The rate of discharge of the reductor motoneurons is increased by sensory stimulation. The PL interneurons form either excitatory or disinhibitory pathways, which are relevant in function to the observed increase of the motoneuron. Conversely, the AL interneurons form either inhibitory or disfacilitatory pathways. Thus, the PL and the AL interneurons are fractionated in function and distinguishable in terms of their physiology by their input and output correlations. Functional meaning of the presence of these two types of unilateral local nonspiking interneurons of opposing connections in the uropod motor control system is discussed.
Effect of prenatal exposure to alcohol on the distribution and time of origin of corticospinal neurons in the rat
Authors: Miller Michael W.
Published: January 2005

The distribution and the time of origin of corticospinal neurons were examined in rats prenatally exposed to ethanol and in control rats. The distribution of corticospinal neurons was determined by tracing the retrograde transport of horseradish peroxidase (HRP) from an injection site in the cervical spinal cord.

In control rats, HRP‐positive neurons were distributed in layer Vb throughout motor area 4, rostral motor area 6/8, dorsal somatosensory area 3, caudal somatosensory area 2, and various “association” regions including parietal areas 14, 39, and 40, occipital areas 18a and 18b, cingulate areas 24a and 24b, and prefrontal area 32. In ethanol‐exposed rats, the distribution of retrogradely labeled neurons was similar to control animals with three notable exceptions: (1) HRP‐positive neurons were evident throughout the rostrocaudal extent of area 6/8; (2) occasionally ectopic labeled neurons were identified in the supragranular layers, layers Va and Vc, and superficial layer VI; and (3) the density of HRP‐labeled neurons and the ratio of labeled neurons to the total number of neurons in areas 4, 6/8, 3, and 2 were significantly greater (20–48%) in ethanol‐exposed rats than in controls. There was, however, no intergroup difference in the area of the cell bodies of HRP‐positive neurons. Taken together, these findings indicate that ethanol exposure resulted in an increased number of corticospinal neurons.

The time of origin of corticospinal neurons was determined by using a technique that combined tritiated thymidine autoradiography and retrograde transport of HRP. In control animals, HRP‐positive neurons were double labeled by an injection of tritiated thymidine on gestational day (GD) 15, 16, or 17. In ethanol‐exposed rats, corticospinal neurons were generated on GD 16, 17, and 18, the late‐generated ones being distributed in caudal area 6/8.

These intergroup differences represent a persisting ethanol‐induced alteration of cortical structure that may underlie motor dysfunction and mental retardation in fetal alcohol‐affected offspring. Moreover, the increase in the number and the delay in the time of origin of corticospinal neurons suggest that the normal process of paring down exuberant orticospinal projections may be affected by prenatal exposure to ethanol.
Thalamic connectivity of the primary motor cortex of normal and reeler mutant mice
Authors: Terashima Toshio , Inoue Kaoru , Inoue Yoshiro , Mikoshiba Katsuhiko
Published: January 2005

Reeler, an autosomal recessive mutation in mice, causes cytoarchitectonic abnormalities of the cerebral cortex, which are characterized by malposition of neurons. Retrograde and anterograde transport of horseradish peroxidase (HRP) was employed to examine the reciprocal connectivity between the hindlimb area of the primary motor cortex (MI) and thalamus of normal and reeler mutant mice. In the normal mouse, most of the cells labelled after HRP injection into the hindlimb area of MI were located in the ventrolateral nucleus, the lateral division of the ventrobasal nucleus, the central lateral, paracentral and central intralaminar nuclei, and the medial division of the posterior complex. HRP reaction product antero‐gradely transported was also observed in the same nuclei and in the thalamic reticular nucleus. In the reeler mutant mouse, retrogradely labelled neurons and anterogradely labelled terminals were again found in the nuclei referred to above, and the distribution pattern and morphology of HRP‐filled neurons were also similar to those of normal controls. The present results suggest therefore that the normal reciprocal connectivity between MI (hindlimb representation) and thalamus is preserved in the reeler mouse. That is to say, dislocated cortical neurons appropriately project to their target nuclei of the thalamus, and conversely, thalamic neurons send their axons precisely to their target cortical areas of the radially disorganized cortex.
Limb specific connections of the cat magnocellular red nucleus
Authors: Robinson F. R. , Houk J. C. , Gibson A. R.
Published: January 2005

Afferent and efferent connections of the limb specific divisions of the cat magnocellular red nucleus (RNm) were traced using the bidirectional transport of wheatgerm agglutinin‐horseradish peroxidase complex (WGA‐HRP). Injection sites within forelimb or hindlimb RNm regions were identified by microelectrode recording and confirmed by the position of labeled rubrospinal terminals. Additional injections into structures that project to, or receive input from, RNm confirmed the somatotopic organization of these pathways.

The forelimb region of RNm receives input from the posteriolateral part of the anterior interpositus nucleus (NIA) and the intermediate part of the posterior interpositus nucleus (NIP). The hindlimb region of RNm receives input from anteriomedial NIA and medial NIP. Terminals of NIA cells densely fill all of RNm, but terminals of NIP cells form a half shell on the medial, ventral, and posterior borders of RNm without encroaching on RNm's lateral edge or central core. Forelimb and hindlimb RNm are reciprocally connected with the caudal cuneate and gracile nuclei respectively. There is little or no input to RNm from the medial or lateral cerebellar nuclei.

Forelimb RNm, which also contains a face representation, projects to the lateral reticular nucleus, cell group f of the inferior vestibular nucleus, the facial nucleus, the main sensory nucleus of the trigeminal nerve, the caudal cuneate nucleus, the parvicellular reticular formation, and cervical segments of the spinal cord. A few fibers from forelimb RNm project directly to motor neurons in the lower cervical cord. Hindlimb RNm projects to only the lateral reticular nucleus, gracile nucleus, and lower spinal segments. Forelimb and hindlimb RNm project to different regions of the lateral reticular nucleus with some overlap.
An ultrastructural analysis of the sympathetic neuromuscular junctions on arterioles of the submucosa of the guinea pig ileum
Authors: Luff Susan E. , McLachlan Elspeth M. , Hirst G. D. S.
Published: January 2005

The relationship of the varicosities of sympathetic postganglionic nerve terminals to the smooth muscle cells of arterioles in the submucosa of the guinea pig ileum has been investigated quantitatively by electron microscopy. Longitudinal sections were cut through arterioles about 50 m̈m in diameter after fixation in vitro or in situ under pressure. About 13% of the varicosities in individual ultrathin sections made contact with the outer surface of the smooth muscle cells. The neuromuscular junctions resembled those in skeletal muscle: the basal laminae of the axon bundle and of the smooth muscle were fused, and synaptic vesicles were accumulated close to the region of fusion. When individual varicosities were examined in serial sections, 92% and 83% in two preparations were found to form junctions of this kind. Most of the noncontacting varicosities were bare of Schwann cell toward the arteriolar surface and separated from it by > 200 nm. Almost all axon profiles contained synaptic vesicles with electron dense cores after exposure to 5‐hydroxydopamine. In electrophysiological experiments, ionophoretic application of noradrenaline to the arteriolar surface along the nerve bundles (demonstrated subsequently by fluorescence histochemistry) produced responses resembling those evoked by nerve stimulation. These anatomical and physiological data, taken together with the evidence for quantal release in this preparation (see Hirst et al., '85), suggest that neuromuscular transmission involves the rare release of a quantum of noradrenaline at discrete points on the smooth muscle membrane.
Golgi studies on the development of granule cells of the rat olfactory bulb with reference to migration in the subependymal layer
Authors: Kishi Kiyoshi
Published: January 2005

The morphology and the development of the cells in the subependymal layer and of granule cells of the olfactory bulb were examined by Nissl and Golgi staining in postnatal rats. The subependymal layer around the anterior lateral ventricle extends into the center of the olfactory bulb. The mitotic indexes in the subependymal layer are high at the level of the anterior horn of the lateral ventricle and very low inside the olfactory bulb during the first 3 weeks after birth. Golgi‐stained subependymal cells are classified into two main groups. One group consists of smoothly contoured bipolar cells with leading processes tipped by large growth cones and with trailing processes. They make up a majority of Golgi‐stained subependymal cells during the first 3 weeks of age, and smaller numbers of them continue to exist at 37 and 60 days. They migrate with their growth cones oriented toward the olfactory bulb from the level of the anterior lateral ventricle into the granular layer of the olfactory bulb, where they differentiate into the definitive granule cells: their somata enlarge; the leading processes elongate, branch, sprout many gemmules, and become the peripheral processes; and the trailing processes become the basal dendrites. The other group containes relatively large cells with many cytoplasmic processes that are considered to belong to the glial cell line.
Localization of preproenkephalin mRNA in the rat brain and spinal cord by in situ hybridization
Authors: Harlan Richard E. , Shivers Brenda D. , Romano Gary J. , Pfaff D. W. , Howells Richard D.
Published: January 2005

To determine the localization in rat brain and spinal cord of individual neurons that contain the messenger RNA coding for the opioid peptide precursor preproenkephalin, we performed in situ hybridization with a tritiated cDNA probe complementary to a protion of preproenkephalin mRNA. We observed autoradiographic signal over the cytoplasm of neurons of many regions of the central nervous system. Several types of controls indicated specificity of the labeling. Neurons containing preproenkephalin mRNA were found in the piriform cortex, ventral tenia tecta, several regions of the neocortex, nucleus accumbens, olfactory tubercle, caudate‐putamen, lateral septum, bed nucleus of the stria terminalis, diagonal band of Broca, preoptic area, amygdala (especially central nucleus, with fewer labeled neurons in all other nuclei), hippocampal formation, anterior hypothalamic nucleus, perifornical region, lateral hypothalamus, paraventricular nucleus, dorsomedial and ventromedial hypothalamic nuclei, arcuate nucleus, dorsal and ventral premamillary nuclei, medial mamillary nucleus, lateral geniculate nucleus, zona incerta, periaqueductal gray, midbrain reticular formation, ventral tegmental area of Tsai, inferior colliculus, dorsal and ventral tegmental nuclei of Gudden, dorsal and ventral parabrachial nuclei, pontine and medullary reticular formation, several portions of the raphe nuclei, nucleus of the solitary tract, nucleus of the spinal trigeminal tract (especially substantia gelatinosa), ventral and dorsal cochlear nuclei, medial and spinal vestibular nuclei, cuneate and external cuneate nuclei, gracile nucleus, superior olive, nucleus of the trapezoid body, some deep cerebellar nuclei, Golgi neurons in the cerebellum, and most laminae of the spinal cord. In most of these brain regions, the present results indicate that many more neurons contain preproenkephalin mRNA than have been appreciated previously on the basis of immunocytochemistry.
Efferent projections of the suprachiasmatic nucleus: II. Studies using retrograde transport of fluorescent dyes and simultaneous peptide immunohistochemistry in the rat
Authors: Watts Alan G. , Swanson Larry W.
Published: January 2005

In a previous study (Watts et al., '87) we reexamined the projections of the suprachiasmatic nucleus (SCh) with the PHA‐L method and found that they could be divided conveniently into six groups of fibers. By far the densest projection ends just dorsal to the SCh in a comma‐shaped region designated the “subparaventricular zone,” although some fibers continue on through the paraventricular nucleus of the hypothalamus to end in the overlying midline thalamus, and others continue on to end in the dorsomedial nucleus, the region around the ventromedial nucleus, and the posterior hypothalamic area. Other relatively sparse projections from the SCh were also described to the preoptic region, lateral septal nucleus, parataenial and paraventricular nuclei of the thalamus, and ventral lateral geniculate nucleus. In addition, the same method was used to show that the subparaventricular zone projects in turn massively to these same regions, as well as back to the SCh itself and to the periaqueductal gray.

The present series of experiments was designed to confirm these observations with retrograde tracer injections and to investigate the cellular and possible neurotransmitter organization of the major projections from the SCh and subparaventricular zone with a combined retrograde tracer‐immunohistochemical method. For this, the distribution of neuronal cell bodies within the SCh that stain with antisera to vasopressin, vasoactive intestinal polypeptide (VIP), corticotropin‐releasing factor, bombesin, substance P, neurotensin, somatostatin, thyrotropin‐releasing hormone, and angiotensin II was described in detail first. Then the distribution of retrogradely labeled neurons that were also stained for one or another of these peptides was described after injections of true blue, or in some cases SITS, into the regions of the subparaventricular zone, the paraventricular and parataenial nuclei of the thalamus, the ventromedial nucleus, the dorsomedial nucleus, and the periaqueductal gray. The results confirm previous immunohistochemical and anterograde tracing studies and in addition indicate that cells in dorsal as well as ventral parts of the SCh project to each of the terminal fields examined, as do many cells in surrounding areas, including the subparaventricular zone. Our results also suggest that, at the very least, vasopressin‐, VIP‐, and neurotensin‐stained cells in the SCh project to the subparaventricular zone, midline thalamus, and dorsomedial nucleus, and that the vasopressin and VIP‐stained fiber systems are partially segregated at the level of the subparaventricular zone. Finally, we have shown that neuropeptide‐Y‐stained neurons in the ventral lateral geniculate nucleus (the intergeniculate leaflet) project to the same nucleus on the opposite side of the brain.
GABAergic neurons and axon terminals in the brainstem auditory nuclei of the gerbil
Authors: Roberts Rosalinda C. , Ribak Charles E.
Published: January 2005

The anatomical localization of glutamic acid decarboxylase (GAD), the synthesizing enzyme for GABA, was analyzed in the brainstem auditory nuclei of the adult gerbil. GAD‐positive terminals and somata were present in the cochlear nucleus, superior olivary complex, lateral lemniscus, and inferior colliculus in varying concentrations and patterns. One of the highest densities of GAD‐positive terminals is found in the superficial layers of the dorsal cochlear nucleus (DCN), whereas the ventral cochlear nucleus (VCN) has somewhat fewer terminals that are arranged in pericellular plexuses. GAD‐positive neurons occur mainly in the superficial and fusiform layers of the DCN and are scattered throughout the VCN. Within the superior olivary complex, the highest concentration of immunoreactive terminals and neurons occurs in the ventral and lateral nuclei of the trapezoid body. In contrast, the medial nucleus of the trapezoid body and the medial superior olive contain fewer GAD‐positive puncta and probably no immunoreactive somata. The lateral superior olive and superior periolivary nucleus contain a few immunoreactive puncta but a large number of immunoreactive somata. In the midbrain, the nuclei of the lateral lemniscus contain a moderate number of GAD‐positive puncta and a large number of different types of GAD‐positive neurons. The inferior colliculus also contains a heterogeneous population of labeled somata, most of which are multipolar neurons. In addition, a high concentration of immunoreactive puncta occurs in this region. These data demonstrate a diverse distribution of GAD‐positive neurons and puncta throughout the brainstem auditory nuclei and suggest that GABA might be an important neurotransmitter in the processing of auditory information.
Variability in hand surface representations in areas 3b and 1 in adult owl and squirrel monkeys
Authors: Merzenich Michael M. , Nelson Randall J. , Kaas Jon H. , Stryker Michael P. , Jenkins William M. , Zook John M. , Cynader Max S. , Schoppmann Axel
Published: January 2005

Detailed microelectrode maps of the hand representation were derived in cortical areas 3b and 1 from a series of normal adult owl and squirrel monkeys. While overlap relationships were maintained, and all maps were internally topographic, many map features varied significantly when examined in detail. Variable features of the hand representations among different monkeys included (a) the overall shapes and sizes of hand surface representations; (b) the actual and proportional areas of representations of different skin surfaces and the cortical magnifications of representations of specific skin surfaces, which commonly varied severalfold in area 3b and manyfold in area 1; (c) the topographic relationships among skin surface representations, with skin surfaces that were represented adjacently in some monkeys represented in locations many hundreds of microns apart in others; (d) the internal orderliness of representations; (e) the completeness of representations of the dorsal hand surfaces; and (f) the skin surfaces represented along the borders of the hand representation.

Owl monkey maps were, in general, internally more strictly topographic than squirrel monkey maps. In both species, area 3b was more strictly topographic and less variable than was area 1.

The degree of individual variability revealed in these experiments is difficult to reconcile with the hypothesis that details of cortical maps are ontogenetically specified during a period in early life. Instead, we propose that differences in the details of cortical map structure are the consequence of individual differences in lifelong use of the hands. This conclusion is consistent with earlier studies of the consequences of peripheral nerve transection and digital amputation, which revealed that cortical maps are dynamically maintained and are alterable as a function of use or nerve injury in these monkeys (Merzenich et al., '83a, b, '84a; Merzenich, '86; Jenkins et al., '84; Jenkins and Merzenich, '87).
Demarcations of the mechanosensory projection zones in the raccoon thalamus, shown by cytochrome oxidase, acetylcholinesterase, and Nissl stains
Authors: Wiener Sidney I. , Johnson John Irwin , Ostapoff E.‐Michael
Published: January 2005

To determine anatomically the boundaries and internal organization of the kinesthetic and cutaneous mechanosensory regions of the ventrobasal thalamus, alternate section series from electrophysiologically mapped tissues from 14 raccoons were stained for cytochrome oxidase, myelinated fibers, acetylcholinesterase, and Nissl substance. Microelectrode tracks, along with electrolytic lesions placed as tissue markers, reveal that (1) the mechanoreceptor projection zones have higher cytochrome oxidase and lower acetylcholinesterase staining than some neighboring regions. Both these enzymatic stains reveal particularly sharp boundaries separating the mechanoresponsive region, from the lateral posterior nucleus dorsally and from the ventroposterior inferior nucleus ventrally. (2) The kinesthetic projection zone is often separated from other mechanoreceptor projections by bundles as well as laminae of myelinated fibers, similar to those separating cutaneous projections from distinct body parts. These subdivisions are particularly well marked by the cytochrome oxidase stain. The combination, in neighboring sections, of the use of the several stains adds considerably to the visible delineation of these functionally distinct regions, beyond what can be seen in Nissl‐stained sections.
Cortical and subcortical afferent connections of a posterior division of feline area 7 (Area 7p)
Authors: Olson C. R. , Lawler K.
Published: January 2005

Area 7 of the cat, as identified cytoarchitecturally, includes cortex both on the middle suprasylvian gyrus and on the anterior lateral gyrus. The aim of the experiments reported here was to determine whether within this zone there are subdivisions with qualitatively different patterns of afferent connectivity. Deposits of distinguishable retrograde tracers were placed at 29 sites in and around area 7 of 15 cats; cortical and subcortical telencephalic structures were then scanned for retrograde labeling. Our results indicate that cortex on the anterior lateral gyrus, although often included in area 7, is indistinguishable on connectional grounds from adjacent somesthetic cortex (area 5b), Cortex with strong links to visual, oculomotor, and association areas is confined to the middle suprasylvian gyrus and the adjacent lateral bank of the lateral sulcus. We refer to this discrete, connectionally defined zone as posterior area 7 (area 7p).

Area 7p receives input from visual areas 19, 20a, 20b, 21a, 21b, AMLS, ALLS, and PLLS; from frontal oculomotor cortex (areas 6m and 61); and from cortical association areas (posterior cingulate cortex, the granular insula, the posterior ectosylvian gyrus, and posterior area 35). Thalamic projections to area 7p arise from three specific nuclei (pulvinar; nucleus lateralis intermedius, pars caudalis; nucleus ventralis anterior) and from the intralaminar complex (nuclei centralis lateralis, paracentralis and centralis medialis). Neurons in a division of the claustrum immediately beneath the somatosensory and visual zones project to area 7p. Within area 7p, anterior‐posterior regional differentiation is present, as indicated by the spatial ordering of projections from cingulate and frontal cortex, the thalamus, and the claustrum.

Area 7p, as delineated by connectional analysis in this study, resembles cortex of the primate inferior parietal lobule both in its location relative to other cortical districts and in its pattern of neural connectivity.
The distribution of proenkephalin‐derived peptides in the central nervous system of turtles
Authors: Reiner Anton
Published: January 2005

The present study was carried out to examine if peptides similar to the various opioid peptide products of mammalian proenkephalin are present in the turtle central nervous system and to determine their distribution. Antisera against several enkephalin peptides were used: (1) leucine‐enkephalin (LENK), (2) methionine‐enkephalin (MENK), (3) methionine‐enkephalin‐arg6‐phe7 (MERF), (4) methionine‐enkephalin‐arg6‐gly7‐leu8 (MERGL), (5) Peptide E (PEPE), and (6) BAM22P. Their specificity and cross‐reactivity were carefully examined. The results indicated that LENK, MENK, and MERF (or highly similar peptides) are present in the turtle central nervous system, and that a peptide showing immunological similarity to BAM22P and PEPE also appeared to be present. In contrast, MERGL did not appear to be present. The distributions of the immunoreactive labeling for LENK, MENK, MERF, BAM22P, and PEPE were indistinguishable, and double‐label studies showed that LENK, MERF, and BAM22P were colocalized within individual neurons and fibers. Although all of the above substances were observed in the same cell groups, there was some regional variation, in terms of which enkephalin peptide appeared to be most abundant.

The distributions of these enkephalin peptides were very similar to those previously described in mammals and birds. Enkephalin was more abundant in the basal ganglia than in overlying telencephalic regions. Within the basal ganglia, enkephalin was present in striatal neurons and fibers and in pallidal fibers, thereby suggesting the existence of an enkephalinergic striatopallidal projection. Sensory relay nuclei of the thalamus were generally poor in enkephalinergic fibers, whereas the hypothalamus was rich in enkephalinergic neurons and fibers. Enkephalinergic neurons and fibers were present in the midbrain central gray. As is true of neurons of the nucleus spiriformis lateralis of the avian pretectum, the neurons of the homologous cell group in turtles, the dorsal nucleus of the posterior commissure of the pretectum, were found to contain enkephalin and have an enkephalinergic projection to the deep layers of the ipsilateral tectum. Enkephalinergic neurons and fibers were also abundant in the entry zones of the trigeminal nerve and dorsal root fibers of the spinal cord.

The present results indicate that: (1) consistent with previously published biochemical studies (Lindberg and White, '86), proenkephalin in reptiles is similar in structure to that of mammals and, with the exception of MERGL, gives rise to similar or identical enkephalin peptides, and (2) the enkephalin peptides are found in many of the same systems of reptilian brain as mammalian and avian brain, and, therefore, may play a role in similar functions (e.g., basal ganglia motor functions) as in mammals and birds.
Identification of abducens motoneurons, accessory abducens motoneurons, and abducens internuclear neurons in the chick by retrograde transport of horseradish peroxidase
Authors: Labandeira‐Garcia J. L. , Guerra‐Seijas M. J. , Segade L. A. G. , Suarez‐Nuñez J. M.
Published: January 2005

The location of the motoneurons innervating the lateral rectus, pyramidalis, and quadratus muscles of the chick has been determined by application of horseradish peroxidase (HRP) to these muscles and their nerve branches, and internuclear neurons in the abducens nucleus have been identified by injection of HRP into the oculomotor nucleus. Quantitative results were obtained by means of a semiautomatic image analyzer. Lateral rectus motoneurons were observed only in the ipsilateral principal abducens nucleus, where they numbered 500–550, and quadratus and pyramidalis motoneurons only in the ipsilateral accessory abducens nucleus. The 325–375 internuclear neurons that appeared in the principal abducens nucleus contralateral to the oculomotor nucleus injected with HRP were practically confined to the rostral two thirds of the nucleus, where they tended to surround the lateral rectus motoneurons in dorsal or lateral positions, though a minority of interneurons also mingled with the motoneurons in the center or at the medial face of the nucleus. Most interneurons were small and elongated, but a minority of larger interneurons morphologically similar to the lateral rectus motoneurons were also distinguishable. The 100–110 quadratus motoneurons and the 45–55 pyramidalis motoneurons mingled in the accessory abducens nucleus were larger than the lateral rectus motoneurons and sent their axons into the ipsilateral abducens nerve.
Ventromedial mesencephalic tegmental (VMT) projections to ten functionally different cortical areas in the cat: Topography and quantitative analysis
Authors: Scheibner Tethys , Törk István
Published: January 2005

The cortical projections of the ventromedial mesencephalic tegmentum (VMT) were studied in the cat by the retrograde transport of wheat germ agglutinin‐conjugated HRP (WGA‐HRP). The following cortical regions were injected: prefrontal, cingulate, motor, somatic sensory, auditory, primary visual, secondary visual, parasplenial, insular, and entorhinal. Labelled cells in the five component nuclei of the VMT (rostral linear, parabrachial pigmented, central linear, interfascicular, and paranigral nuclei) were counted and the numbers correlated with the total cell populations of the nuclei.

In all experiments large numbers of cells were labelled in the VMT, particularly in the rostral linear and parabrachial pigmented nuclei. Following entorhinal cortical injections, significant labelling occurred in the interfascicular and central linear nucleus, although some cells of these nuclei were labelled in every experiment. The cells of the paranigral nucleus remained unlabelled in all experiments. Several hundred VMT cells were labelled in most experiments, over 1000 in the case of the parasplenial and over 2000 in the case of prefrontal injections. The most strongly labelled nucleus was the rostral linear, in which up to 36% of the total cell population could be labelled in a single experiment.

These results indicate that the VMT of the cat is a major source of brainstem projections to the cerebral cortex and that all cortical areas are reached by this system. Although the projections to the prefrontal and limbic cortical areas are particularly prominent, there appears to be a consistent and significant projection to all areas. Further, the projection of the VMT to the cortex is topographically organized, indicating that the functional roles of the component nuclei of the VMT may be substantially different.
Cobaltic lysine study of the morphology and distribution of the cranial nerve efferent neurons (motoneurons and preganglionic parasympathetic neurons) and rostral spinal motoneurons in the Japanese toad
Authors: Oka Yoshitaka , Takeuchi Hiroaki , Satou Masahiko , Ueda Kazuo
Published: January 2005

The morphology and distribution of the cranial nerve motoneurons (except III, IV, and VI) and rostral spinal motoneurons were systematically studied in the Japanese toad (Bufo japonicus) by retrograde labelling with cobaltic lysine complex. The cobaltic lysine clearly labelled whole neurons, i.e., cell bodies, proximal and distal dendrites, and axons. The branchial motoneurons (V, VII, IX, and X) had similar morphological characteristics and formed a more‐or‐less continuous cell column through the brainstem. The dendrites could be grouped mainly into the dorsomedial and the ventrolateral dendritic arrays. The dorsomedial dendrites formed a dendritic plexus in the subependymal gray matter, which extended as far peripherally as beneath the ependymal layer. The ventrolateral dendrites formed a broom‐like dendritic plexus in the lateral to ventrolateral white matter. They usually extended as far peripherally as the pial surface. The rostrocaudal extent of the dendritic field was also wide and usually exceeded the motor nuclear boundaries. The hypoglossal motoneurons were grouped into the dorsomedial and ventrolateral cell groups, and the latter was considered to be part of the rostral spinal motoneuron column, from their morphology and distribution. The former had well‐differentiated dendrites and occupied a more medial position than the branchial motoneurons. Besides the equivalent of the dorsomedial and ventrolateral dendritic arrays of the branchial motoneurons, they had dorsal and commissural dendrites. The accessory motoneurons had morphological characteristics and a distribution pattern similar to those of the rostral spinal motoneurons rather than the branchial motoneurons. The rostral spinal motoneurons had morphological characteristics somewhat different from the branchial motoneurons and the hypoglossal motoneurons (dorsomedial group). Functional implications of the motoneuron morphology are discussed, mainly based on the present results and earlier anatomical and physiological studies of the spinal motoneurons.

The present study also revealed the anatomical features of the preganglionic parasympathetic neurons supplying some cranial nerves. These neurons had small somata with less elaborate dendrites and formed an almost continuous cell column that occupied a more dorsal position than the motoneurons of the corresponding nerve. They are thought to be homologous to the salivatory nucleus and the dorsal motor nucleus of the vagus. The basic anatomical organization of the general visceral efferent column seems to be similar throughout vertebrates.
Pedunculopontine tegmental nucleus of the rat: Cytoarchitecture, cytochemistry, and some extrapyramidal connections of the mesopontine tegmentum
Authors: Rye David B. , Saper Clifford B. , Lee Henry J. , Wainer Bruce H.
Published: January 2005

The pedunculopontine tegmental nucleus (PPTn) was originally defined on cytoarchitectonic grounds in humans. We have employed cytoarchitectonic, cytochemical, and connectional criteria to define a homologous cell group in the rat. A detailed cytoarchitectonic delineation of the mesopontine tegmentum, including the PPTn, was performed employing tissue stained for Nissl substance. Choline acetyltransferase (ChAT) immunostained tissue was then analyzed in order to investigate the relationship of cholinergic perikarya, dendritic arborizations, and axonal trajectories within this cytoarchitectonic scheme. To confirm some of our cytoarchitectonic delineations, the relationships between neuronal elements staining for ChAT and tyrosine hydroxylase were investigated on tissue stained immunohistochemically for the simultaneous demonstration of these two enzymes.

The PPTn consists of large, multipolar neurons, all of which stain immunohistochemically for ChAT. It is present within cross‐sections that also include the A‐6 through A‐9 catecholamine cell groups and is traversed by catecholaminergic axons within the dorsal tegmental bundle and central tegmental tract. The dendrites of PPTn neurons respect several nuclear boundaries and are oriented perpendicularly to several well‐defined fiber tracts. Cholinergic axons ascend from the mesopontine tegmentum through the dorsal tegmental bundle and a more lateral dorsal ascending pathway. A portion of the latter terminates within the lateral geniculate nucleus.

It has been widely believed that the PPTn is reciprocally connected with several extrapyramidal structures, including the globus pallidus and substantia nigra pars reticulata. Therefore, the relationships of pallidotegmental and nigrotegmental pathways to the PPTn were investigated employing the anterograde autoradiographic methodology. The reciprocity of tegmental connections with the substantia nigra and entopeduncular nucleus was investigated employing combined WGA‐HRP injections and ChAT immunohistochemistry.

The pallido‐ and nigrotegmental terminal fields did not coincide with the PPTn, but, rather, were located just medial and dorsomedial to it (the midbrain extrapyramidal area). The midbrain extrapyramidal area, but not the PPTn, was reciprocally connected with the substantia nigra and entope‐duncular nucleus. We discuss these results in light of other cytoarchitec‐tonic, cytochemical, connectional, and physiologic studies of the functional anatomy of the mesopontine tegmentum.
Visual topography of V1 in the Cebus monkey
Authors: Gattass Ricakdo , Sousa Aglai P. B. , Rosa Marcello G. P.
Published: January 2005

The representation of the visual field in the striate cortex (VI) was mapped with multiunit electrodes in the Cebus monkey. Nine Cebus apella, anesthetized with N2O and immobilized with pancuromium bromide were studied in repeated recording sessions.

In each hemisphere, VI contains a continuous representation of the contralateral visual hemifield. The representation of the vertical meridian (VM) forms the external border of V1 except at the anteriormost portion of the calcarine fissure. The representation of the horizontal meridian (HM) divides the area so that the representation of the lower visual field is located dorsally, and that of the upper field ventrally.

The convoluted surface of VI can be only partially unfolded, and no precise “flattened” map can be obtained without introducing surface discontinuities. The visual topography of VI is presented in a series of coronal sections and in “flattened” maps.

The representation of the central visual field is magnified relative to that of the periphery in VI. The evaluation of the cortical magnification factors measured along isoeccentric and isopolar dimensions in the partially unfolded model of VI revealed anisotropies in the representation of the visual field with larger magnification along isopolar lines than along isoeccentric lines. Receptive field size increases with increasing eccentricity, whereas point image size decreases with increasing eccentricity.
Increased electrotonic coupling in aged rat hippocampus: A possible mechanism for cellular excitability changes
Authors: Barnes C. A. , Rao G. , McNaughton B. L.
Published: January 2005

The effects of aging on the intercellular transfer of the low molecular weight fluorescent dye 5,6‐carboxyfluorescein was studied in subfields fascia dentata, CA1, and CA3 of rat hippocampal slices maintained in vitro. All three areas exhibited a statistically significant increase in dye coupling with age. The increased dye coupling was accompanied by an apparent increase in postsynaptic excitability as assessed by the ratio of the population spike to EPSP components of the extracellulary recorded field potential. The possibility that artifaciual dye coupling due to cell fusion contributed significantly to these results was ruled out by the demonstrations that a high molecular weight, dextran‐coupled fluorescein compound did not produce multiple fills and that dye coupling with carboxyfluorescein could be prevented by prior intracellular loading with Ca++, a procedure that decouples gap junctions in other tissue. The increase in extent of electrical coupling suggested by these data may largely account for the apparent increase in cellular excitability of this tissue with age and may reflect the mechanism by which the senescent hippocampus compensates for the loss of afferent input during the course of normal aging. The additional possibility is raised that increased electrical couping may reflect a mechanism for permanent associative storage of information in this system.
Neuropeptide Y‐immunoreactive perikarya and nerve terminals in the rat medulla oblongata: Relationship to cytoarchitecture and catecholaminergic cell groups
Authors: Häurfstrand A. , Fuxe K. , Terenius L. , Kalia M.
Published: January 2005

The aim of this study was to examine details of the distribution of neuropeptide Y (NPY)‐immunoreactive perikarya and nerve terminals in the medulla oblongata in relation to cytoarchitectonically and functionally distinct catecholaminergic regions. The immunoperoxidase method was combined with Nissl staining to determine nuclear boundaries of transmitter‐identified nerve cell bodies and to examine the relationship between populations of NPY‐immunoreactive neurons and catecholaminergic cell groups (A1, A2, C1, C2, and C3) in serial sections. Previous studies using immunofluorescence have described the existence of NPY catecholaminergic immunoreactive nerve cell bodies in the brainstem. No information is currently available with regard to details of the distribution of these peptidergic neurons and nerve terminals in the functional subnuclear units of the medulla oblongata. In this study we have delineated the anatomical association of NPY immunoreactivity with cardiovascular function. Neuropeptide Y‐immunoreactive neurons were found located in close association with noradrenergic neurons of the Al cell group in the caudal ventrolateral medulla oblongata, where they were usually found located dorsal to the lateral reticular nucleus (LRt). A second population of NPY‐immunoreactive neurons was found located medial to the Al cell group in the ventral subdivision of the reticular nucleus of the medulla (MdV). Neuropeptide Y‐immunoreactive neurons in the rostral medulla were found located in regions corresponding to the principal distribution of adrenergic neurons in the C1, C2, and C3 cell groups. In the dorsomedial medulla (A2 region) NPY‐immunoreactive neurons were localized in the area postrema (ap) and in a number of subnuclei of the nucleus of the tractus solitarius (nTS), i.e., the dorsal parasolitary region (dPSR), the dorsal strip (ds), the periventricular region (PVR), and the ventral parasolitary region (vPSR). The location of NPY‐immunoreactive perikarya and nerve terminals in the dorsal subnuclei of the nTS, i.e., the dPSR and ds, is of particular significance, since this distribution corresponds with the location of small adrenergic neurons as well as with the site of termination of aortic and carotid sinus nerve afferent fibers. NPY‐immunoreactive neurons in the dorsomedial medulla are ideally situated for receiving monosynaptic input from baroreceptor afferents and could play a key role in the central integration of cardiovascular reflexes.