bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for a viscerotopic sensory representation in the cortex and thalamus in the rat
Authors: Cechetto David F. , Saper Clifford B.
Published: January 2005

The functional organization of the insular cortex was studied by recording neuronal responses to visceral sensory stimuli. Horseradish peroxidase (HRP) was then iontophoresed at the recording sites to identify afferents from the ventrobasal thalamus to specific visceroceptive sites in the insular cortex. The relationship of the ventrobasal thalamus to the insular cortex and to brainstem relay nuclei for the ascending visceral projections was then examined by using the axonal transport of HRP, wheat germ agglutinin conjugated to HRP (WGA‐HRP), and fluorescent dyes. Of a total of 55 neurons that were tested for responses to visceral sensory stimuli, 33 units responded to atleast one visceral sensory modality: 6 received gastric mechanoreceptor input, 8 responded to taste inputs, 13 were activated by arterial chemoreceptors and/or showed respiratory related activity, and 6 responded to cardiovascular baroreceptor stimulation. On the basis of its cytoarchitecture and connections with the thalamus, the insular cortex was divided into a dorsal granular area, an intermediate dysgranular region, and a ventral agranular strip. Taste‐responsive neurons were located anteriorly, primarily in the dysgranular region, whereas unit responses to general visceral modalities were distributed dorsally and posteriorly in the granular insular cortex. Gastric mechanoreceptor‐responsive units were situated more dorsally and anteriorly in the granular insular cortex, while cardiopulmonary inputs were located more ventrally and posteriorly. Injections of HRP into the gustatory insular cortex resulted in retrograde labeling of neurons in the parvicellular part of the ventroposterior medial thalamic nucleus (VPMpc). Injections into the general visceral insular cortex retrogradely labeled neurons lateral to VPMpc in the ventroposterior lateral parvicellular thalamic nucleus (VPLpc). Injections of HRP, WGA‐HRP, and fluorescent dyes into VPMpc and VPLpc verified that their projection to the insular cortex is topographically organized. In the same experiments, retrogradely labeled neurons in the parabrachial nucleus identified the likely subnuclei within this nucleus for relay of visceral sensory information to the thalamus. Injections of WGA‐HRP into the parabrachial nucleus demonstrated that its projection to the ventrobasal thalamus is also topographically organized. These results demonstrate the relationship of general visceral and special visceral (taste) representations in the insular cortex. The ascending pathway for visceral sensory information appears to be viscerotopically organized at all levels of the neuraxis, including the insular cortex.
Forms and spatial arrangement of neurons in the primary motor cortex of man
Authors: Meyer Gundela
Published: January 2005

The morphology and the spatial arrangement of neurons in the primary motor cortex (area 4) of the adult human brain have been investigated by the Golgi method. The human motor cortex displays a great variety of pyramidal and nonpyramidal cells, expressed as important differences in soma shape and size, and in the dimensions and the distribution of dendritic trees, which are described in detail. The neuronal composition of each layer and the white matter is analyzed. In sublayers III b and c, the somata and dendritic trees of pyramidal and nonpyramidal cells are grouped into columnar aggregations, 100–300 μm wide and separated by cell‐sparse spaces of 50–100 μm width. Within the aggregations, the apical dendrites of pyramidal cells form several bundles. The dendrites of most nonpyramidal cells do not surpass the columnar width. Sections in different planes reveal that the columnar aggregations observed in sections perpendicular to the long axis of the precentral gyrus are actually the cross‐sectioned representatives of elongate strips running parallel to the long axis of the gyrus. The dendrites and somata of pyramidal cells in layers III and V show a preferential orientation in the same direction, parallel to the main axis of the gyrus. In layers II, IV, and V, aggregations like those in layer III are not recognizable; however, in layer V, loose assemblages of neurons of all sizes group around the giant Betz cells. Layer VI has a radial appearance due to the radii of myelinated fibers entering and leaving the white matter. The vertical, columnar organization of layer III and the asymmetry of somata and dendritic trees are not observed consistently throughout area 4, but are more pronounced at the boundary of the precentral gyrus and the central sulcus.
Comparative distribution of dopamine D‐1 and D‐2 receptors in the basal ganglia of turtles, pigeons, rats, cats, and monkeys
Authors: Richfield Eric K. , Young Anne B. , Penney John B.
Published: January 2005

The distribution and density of dopamine D‐1 and D‐2 receptors were studied in the basal ganglia of adult turtles, pigeons, rats, cats, and monkeys. Dopamine receptors were measured in vitro by quantitative autoradiography in alternate sections processed for D‐1 and D‐2 receptor subtypes and compared to adjacent sections stained for acetylcholinesterase (AChE) activity. [3H]‐SCH 23390 and [3H]‐spiroperidol were used to label the D‐1 and D‐2 dopamine receptor subtypes, respectively.

The anatomic distribution of both D‐1 and D‐2 receptors in the basal ganglia was remarkably similar across all species examined. Whereas the absolute number of D‐1 and D‐2 receptors in the basal ganglia varied between species, the percentage of D‐1 and D‐2 receptors in a region was quite similar among species.

The pattern of binding to the D‐1 and D‐2 receptor varied among the different species. The adult turtles, pigeons, and rats demonstrated non‐patchy D‐1 and D‐2 receptor binding in the striatum and pallidum. The adult cat and monkey caudate nucleus and putamen demonstrated mildly heterogeneous receptor binding in a pattern that differed from that seen with AChE staining, but did occasionally demonstrate similar patterns of the D‐1 and D‐2 receptor subtypes, The immature cat striatum was characterized by heterogeneous D‐1 receptor binding that corresponded to heterogeneous AChE rich patches, whereas D‐2 receptor binding was homogeneous.

Heterogeneous binding was seen in other basal ganglia structures including the nucleus accumbens, olfactory tubercle, and substantia nigra pars compacta and reticulata. Complementary D‐1 and D‐2 receptor binding patterns were seen in the pallidum and substantia nigra of the mammals.

The results of this study indicate that both D‐1 and D‐2 dopamine receptors are present in the basal ganglia of five different vertebrates. A common feature of dopamine receptors in the basal ganglia is their heterogeneity in distribution and density. The heterogeneity of dopamine receptors has similarities to and differences from the distribution of presynaptic dopamine and other neurotransmitter markers of the basal ganglia.
Morphological analysis of the tuberomammmillary nucleus in the rat brain: Delineation of subgroups with antibody again L‐histidine decarboxylase as a marker
Authors: Ericson H. , Watanabe T. , Köhler C.
Published: January 2005

With an antibody specific for L‐histidine decarboxylase (HD) in combination with immunohistochemical techniques and retrograde fluorescent tracing, the morphology, distribution, and projections of the histamineragic neurons of the posterior hypothalamus were studied in the adult male rat.

Magnocellular neurons, situated on both sides of the mammillary recess and close to the ventral surface of the brain rostral and caudal to the mammillary bodies, were found to contain HD‐immunoreactivity (HD‐i). In addition to these magnocellular neurons, a substantial number of small and medium‐sized neurons were immunostained, as were strands of cells of all sizes bridging the HD‐i cell groups: A detailed mapping of the HD‐i cells in frontal, sagittal, and horizontal sections showed that these neurons make up one continuous cell group, defined as the tuberomammillary nucleus (TM). This nucleus can be divided into several subgroups. Thus, approximately 600 HD‐i neurons situated on each side of the mammillary recess compose the medial subgroup of the TM (TMM). The ventral subgroup of the TM (TMV) consists of some 1,500 neurons situated at the ventral surface of the brain, rostral (TMVr) and caudal (TMVC) to the mammillary bodies. The TMM contains a greater proportion of parvicellular neurons compared to the TMV. About 100 HD‐i cells are scattered within the lateral hypothalamic area, the posterior hypothalamic region, the perifornical area, the supramammillary nucleus, and the dorsomedial hypothalamic nucleus. These cells are collectively named the diffuse part of the TM (TMdiff).

The morphological differences between the TMM and the TMV did not signal differences in the efferent connections of these subgroups. Thus, single injections of the fluorescent tracer Fast Blue into different regions of the brain, including the spinal cord, resulted in retrograde labeling of HD‐i neurons, which were distributed throughout the TM with no discernible topographic pattern. More specifically, each subgroup of the TM contributed projections innervating or passing through a large number of brain regions, including the olfactory bulb, hippocampus, caudate nucleus, paraventricular and supraoptic nuclei of the hypothalamus, cerebellum, tectum, medulla, and spinal cord. The widespread projections of the HD‐i neurons contrasted to the more specific projections observed from non HD‐i neurons in cell groups situated around the TM.

Taken together, these findings suggest that the HD‐i cells of the posterior hypothalamus constitute one major nucleus, the TM, and that this nucleus may be subdivided into three components, each of which has diffuse projections throughout the neuraxis.
Primary afferent and propriospinal fibers in the rat dorsal and dorsolateral funiculi
Authors: Chung Kyungsoon , Langford Lauren A. , Coggeshall Richard E.
Published: January 2005

The purpose of this study is to determine the numbers of primary afferent and propriospinal fibers in the dorsal and dorsolateral funiculi of the rat. The reason for concentrating on these areas is that they contain large numbers of unmyelinated axons. Our data are axonal numbers from the S2 segment of spinal cord in animals that had unilateral dorsal rhizotomies or spinal cord isolations. The major conclusions are (1) that 23% of the primary afferent fibers in the dorsal funiculus are unmyelinated; (2) that there are approximately 12,500 unmyelinated primary afferent fibers in the dorsolateral funiculus, which is more than the number of primary afferent fibers in the dorsal funiculus and tract of Lissauer combined, and (3) that approximately 25% of the axons in the dorsal funiculus and 44% of the axons in the dorsolateral funiculus are propriospinal. These data modify and extend previous ideas of the organization of spinal white matter.
Development of the sex difference in neuron numbers of the superior cervical ganglion: Effects of transection of the cervical sympathetic trunk
Authors: Wright L. L.
Published: January 2005

The number of superior cervical ganglion (SCG) neurons does not differ for males and females on the day of birth, but by 15 days, after most of the normal neuron death has occurred, males have significantly more neurons than females. This difference persists in the adult. The present study was undertaken to determine whether the presence of afferent input to the SCG is required for the development of this sex difference.

Bilateral transection of the cervical sympathetic trunk, which deafferents the SCG neurons, or a sham operation was performed on male and female Sprague Dawley rats on the day of birth. Numbers of neurons were counted in SCGs of animals sacrificed on either postnatal day 4 or 15, before or after normal development of the SCG sex difference.

At 4 days, the number of SCG neurons in sham‐operated males and females were not different, but by 15 days, females had lost a significant number of neurons, whereas the males had not. Transection of the cervical sympathetic trunk led to a significant loss of over 6,000 SCG neurons by postnatal day 4 in both males and females. Whereas some of this loss is due to axotomy of caudally projecting SCG neurons, at least half of the neuron loss is due to removal of the afferent input, At 15 days, sham‐operated males had significantly more SCG neurons than did sham‐operated females, but the gender difference was not significant in animals with neonatally deafferented ganglia. Thus, the normal development of the gender difference in SCG neuron numbers requires an intact afferent input.
Distribution and organization of cholinergic neurons in the rat forebrain demonstrated by computer‐aided data acquisition and three‐dimensional reconstruction
Authors: Schwaber James S. , Rogers Wade T. , Satoh Keiji , Fibiger H. C.
Published: January 2005

An understanding of the organization of cholinergic neurons in the central nervous system has been an important objective for many years. By developing and applying a new electronic method for mapping tissue sections, we have generated original graphic and quantitative findings on forebrain cholinergic neurons that provide new insight into their distribution and organization. Satoh, Armstrong, and Fibiger (Brain Res. Bull. 11:693–720, 1983) have proposed that in the basal forebrain cholinergic neurons with long axons form a continuum rather than being arranged as a series of discrete nuclear groups. It has been difficult, however, by conventional methods of data analysis and display, to test this hypothesis. By using a digital microscopy system, the position of every cholinergic neuron was marked with 1‐μm resolution in tissue sections taken at 90‐μm or 180‐μm intervals through the entire distribution of these neurons in the forebrain. The three‐dimensional reconstruction of these neurons in context shows them to be distributed as a continuous cell column. The column twists and changes position as it is deformed by adjacent neuronal structures, such that its shape and continuity would not be apparent without reconstruction into a computer graphics model. Complementary analyses of the distribution of cholinergic interneurons in dopamine‐rich regions of the forebrain indicated that there are regional differences between striatal and olfactory tubercle neurons. Cellular morphometry analyses show the population of cholinergic neurons in the rat to be surprisingly homogenous in size, but not in shape. Graphic and quantitative analyses indicated that there is a striking relationship between the distributions of projection and interneuronal cell groups.

We conclude that the basal forebrain cholinergic neurons form a continuum. The chemoarchitecture of this cell group does not conform to the usual cytoarchitectural divisions. The present, results, however, taken together with the findings based on Nissl‐stained sections and connectional and biochemical data, suggest that the region of this neurochemically defined continuum should be reexamined for consideration as a single functional entity or nucleus: a cholinergic basal nuclear complex.
Growth of hippocampal mossy fibers: A lesion and coculture study of organotypic slice cultures
Authors: Zimmer Jens , Gähwiler Beat H.
Published: January 2005

In hippocampal slice cultures, the mossy fibers from the dentate granule cells project as normally to cells in the dentate hilus (CA4) and the hippocampal CA3 pyramidal cells. After lesions in vivo and intracerebral transplantation, the mossy fibers can alter their normal distribution within CA3 and even contact CA1 pyramidal cells. The present study examined whether similar changes could be induced in the more simple, virtual two‐dimensionally organized slice cultures. For this purpose slices of 7‐day‐old hippocampal were prepared and subjected to one of the two following manipulations: (1) transection of the mossy fiber layer in CA3 or (2) rearrangement of the geometrical relations between the dentate granule cells in their potential targets (CA3 and CA1) by coculturing dentate slices with CA3 or CA1 slices. Two to 8 weeks later the distribution of the mossy fiber system was visualized by histochemical Timm sulphide silver staining of the terminals.

The distribution of the mossy fiber system observed in previous studies of ordinary hippocampal slice cultures was confirmed. In addition, mossy fibers were found to cross the cuts through the mossy fiber layer with formation of a reduced number of characteristic Timm‐stained terminals in CA3 distal to the lesion. Close proximity and contiguity of the cut surfaces were important for such growth to occur. Significantly fewer mossy fiber terminals were found when separate slices of dentate and CA3 tissue were joined and grown as cocultures. Similar apposition of slices of dentate and CA1 tissue only rarely resulted in the ingrowth of mossy fibers into CA1. The Timm‐stained mossy fiber terminals were then of subnormal size.

The results show the potentials of the slice culture technique in suplementing lesion and transplant studies in situ. The growth of mossy fibers across a transection of their pathway is thus a new observation, difficult to demonstrate in the brain. The limited growth in the cocultures of aberrant mossy fibers into Cal does, on the other hand, emphasize the importance of close structural contact for the formation of nerve connections, and such contact is apparently more easily obtained in the brain. When the growth of the mossy fibers and that of the cholinergic septohippocampal fibers are compared, it is evident that the cholinergic axons grow better both in vitro and in vivo after lesions and transplantation.
Ascending projections to the mammillary nuclei in the rat: A study using retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase
Authors: Shibata Hideshi
Published: January 2005

Cells of origin of ascending afferents to the mammillary nuclei and the afferents' fields of termination within these nuclei were studied by using retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase in the rat.

The pars compacta of the superior central nucleus projects bilaterally to the median region of the medial mammillary nucleus. The ventral tegmental nucleus projects ipsilaterally to the medial mammillary nucleus, except for its median region, in a topographic manner such that the rostrodorsolateral part of the ventral tegmental nucleus projects to the medial quadrant of the medial mammillary nucleus; the rostroventromedial part projects to the dorsal quadrant; the caudodorsolateral part projects to the ventral quadrant; and the caudoventromedial part projects to the lateral quadrant. These projection fields extend throughout the longitudinal axis of the medial mammillary nucleus, except for its most caudal region, to which only the dorsolateral part of the ventral tegmental nucleus projects. This nucleus also projects topographically to the ipsilateral dorsal premammillary nucleus; the rostral part of the ventral tegmental nucleus projects to the dorsal part of the dorsal premammillary nucleus, whereas the caudal part projects to the ventral part. The periaqueductal gray around the dorsal tegmental nucleus projects bilaterally to the supramammillary nucleus. The pars alpha of the pontine periaqueductal gray projects bilaterally to the peripheral part of the lateral mammillary nucleus, whereas the pars ventralis of the dorsal tegmental nucleus projects ipsilaterally to the lateral mammillary nucleus.

The results show that the tegmentomammillary projections are organized in a gradient fashion, with the rostral to caudal position of cells of origin within the tegmental nuclei of Gudden being reflected by the medial to lateral position of fields of termination within the mammillary nuclei.
Exogenous matrix precursors promote functional nerve regeneration across a 15‐mm gap within a silicone chamber in the rat
Authors: Williams Lawrence R. , Danielsen Nils , Müller Harald , Varon Silvio
Published: January 2005

When silicone regeneration chambers are implanted empty, axonal regeneration fails if the interstump gap length is greater than 10 mm. Previous experiments using the 10‐mm gap model demonstrated that regeneration success correlated with the dimension and/or consistency of the naturally formed acellular fibrin matrix. Both spatial and temporal parameters of regeneration could be stimulated through modifications of the fibrin matrix by prefilling the chambers at the time of implantation either with phosphate‐buffered saline or plasma dialyzed against phosphate‐buffered saline. In the present experiments, similar modification of matrix formation was found to promote successful regeneration across 15‐mm and 20‐mm interstump gap lengths. In addition, prefilling 15‐mm‐gap chambers with dialyzed plasma resulted in a 3.5‐fold increase in the incidence of functional restitution detected at 8 weeks after implantation over the outcome with chambers prefilled with phosphate‐buffered saline.
Primary neurons of the lateral line nerves and their central projections in hagfishes
Authors: Kishida R. , Goris R. C. , Nishizawa H. , Koyama H. , Kadota T. , Amemiya F.
Published: January 2005

The hagfish lateral line system was studied by horseradish peroxidase transganglionic transport. The anterior lateral line nerve innervates the group of lateral line canals situated anteriorly to the eye, and the posterior lateral line nerve innervates the group of canals situated posteriorly to the eye. Although both nerves pass through the muscle fascia at the same point, each runs a different course to the brain. The anterior lateral line nerve runs near the trigeminal nerve and its ganglion is closely attached to the trigeminal ganglion, but both systems are completely independent. The posterior lateral line nerve runs independently of any other cranial nerve and makes a peculiar U‐turn at the point of entry to the brain capsule. The anterior lateral line ganglion contains both cutaneous sensory cells (small to large cells) and lateral line sensory cells (small cells); from this ganglion projections run to both the trigeminal sensory nucleus (fine and thick fibers) and medial nucleus of the area acousticolateralis (fine fibers). The posterior lateral line ganglion contains only small lateral line cells that project fine fibers to the medial nucleus of the area acousticolateralis. There are no efferent components in this lateral line system, and its only afferent terminal field is the medial nucleus of the area acousticolateralis.
Descending projection neurons to the spinal cord of the goldfish, Carassius auratus
Authors: Rao P. D. Prasada , Jadhao A. G. , Sharma S. C.
Published: January 2005

The sources of descending spinal tracts in the goldfish, Carassius auratus, were visualized by retrograde transport of horseradish peroxidase (HRP) administered to the hemisected spinal cord. In the diencephalon, HRP‐positive neurons were identified in the nucleus preopticus magnocellularis pars magnocellularis and ventromedial nucleus of the thalamus of the ipsilateral side. In the mesencephalic tegmentum, a few somata of the contralateral nucleus ruber and several ipsilateral neurons of the nucleus of the median longitudinal fasciculus were labeled. The reticular formation of the rhombencephalon was the major source of descending afferents to the spinal cord. A larger number of neurons were retrogradely labeled in the ipsilateral superior, middle, and inferior nuclei than in the contralateral nuclei. A few raphe neurons and the contralateral Mauthner neuron were also HRP‐positive. The octaval area showed retrogradelyl labeled neurons in the anterior, magnocellular, descending, and posterior octaval nuclei of the ipsilateral side. A large number of neurons in the facial lobe and a few somata located adjacent to the descending trigeminal tract were labeled on the ipsilateral side. The pattern of descending spinal projections in goldfish is comparable to that of tetrapods and suggests that the spinal tracts have originated quite early in the course of vertebrate evolution.
Functional topography of the rat hypothalamic dopamine neuron systems: Retrograde tracing and immunohistochemical study
Authors: Kawano Hitoshi , Daikoku Shigeo
Published: January 2005

The origins of the dopamine (DA)‐containing nerve terminals in the external layer of the median eminence and in the neurointermediate pituitary were determined in rats by a combination of retrograde labeling with wheat germ agglutinin (WGA) and immunohistochemistry for tyrosine hydroxylase (TH) Biotinylated WGA (b‐WGA) was injected into the posterior pituitary (group 1) and into the median eminence (group 2). In group 1 animals, all the magnocellular neurons of the paraventricular, supraoptic, and accessory nuclei, and many parvicellular neurons in the rostral periventricular region (RPR) were labeled with WGA. In group 2 animals, many neurons were labeled in the arcuate nucleus and the RPR, and in a small population of the preoptic‐septal region. In group 1 animals, about 39% of TH neurons in the RPR were labeled with WGA, whereas only a few TH neurons (1%) in the arcuate nucleus were labeled with WGA. In group 2 animals, on the contrary, almost all TH neurons (73%) in the arcuate nucleus carried WGA, whereas in the RPR, only some of the TH neurons (19%) were labeled with WGA. It is concluded that DA neurons involved in the hypothalamic‐anterior pituitary axis are located in the arcuate nucleus; those involved in neuro‐intermediate lobe function in the RPR.
Small vesicle bouton synapses on the distal half of the lateral dendrite of the goldfish mauthner cell: Freeze‐fracture and thin section study
Authors: Tuttle Rebecca , Masuko Sadahiko , Nakajima Yasuko
Published: January 2005

To understand principles of synaptic integration, it is necessary to define the types of synapses on a particular neuron and their distribution. Thin sectioning and double replica freeze‐fracture techniques were employed to characterize the small vesicle bouton (SVB) synapses on the distal half of the Mauthner (M) cell lateral dendrite, which probably mediate a remote dendrite inhibition. Throe morphologically distinct SVB synapses, types A, B, and C, were found. These three SVB synapses form roughly 90% of the synapses on the distal half of the lateral dendrite, with types A and B being most common.

The SVB A synapse is characterized by mostly oval and round synaptic vesicles, a discrete presynaptic active zone with a highly variable shape, and a postsynaptic active zone with no apparent particle aggregate in either the E or P face.

At the SVB B synapse, most of the synaptic vesicles are flat. A very high particle density is present throughout the presynaptic P face, and vesicle attachment sites are dispersed over much of the presynaptic membrane, Postsynaptic P face particle aggregates are subjacent to the presynaptic vesicle attachment sites, and are often large and anastomosing.

The SVB C synapse is characterized by synaptic vesicle profiles that vary from flattened to round. The SVB C cytoplasm was unclouded by the flocculent material that characterized SVBs A and B. The presynaptic active zones at the SVB C synapse are discrete, and macular or oblong. No particle aggregates are apparent in the postsynaptic active zone.

Small, macular particle aggregates were found in nonactive zone regions of the postsynaptic E face of all three types of SVBs. Small subsurface cisterns were also observed underlying the M cell membrane at all three types of SVB synapses. Neither the postsynaptic E face aggregates nor the subsurface cisterns were ever observed directly subjacent to presynaptic active zones, but were often seen adjacent to active zones.

Short, straight rows of particles and short cylinders were often seen in both pre‐ and postsynaptic surrounding zone regions of SVB A and C synapses. These structures are thought to represent tight junctions.
Serotonin‐ and substance P‐containing projections to the nucleus tractus solitarii of the rat
Authors: Thor Karl B. , Helke Cinda J.
Published: January 2005

The objective of the present study was to determine the location of the neurons that give rise to serotonin‐ and substance P‐containing terminals in the nucleus tractus solitarii. This was done by injecting rhodamine‐filled latex microspheres into the nucleus tractus solitarii of rats to retrogradely label neuronal cell bodies and by processing sections from the brains of these animals to determine whether the labelled neurons contained serotonin or substance P immunoreactivity. Serotonin‐immunoreactive neurons that projected to the nucleus tractus solitarii were found in the nucleus raphe magnus, nucleus raphe obscurus, nucleus raphe pallidus, and in the ventral medulla, lateral to the pyramidal tract. Substance P‐immunoreactive neurons that projected to the nucleus tractus solitarii were found in similar areas but were proportionately less numerous in the nucleus raphe magnus and proportionately more numerous in the nucleus raphe pallidus. It is concluded that neurons in the medullary raphe nuclei, some of which presumably utilize serotonin or substance P as a neurotransmitter, could regulate autonomic function via direct projections to the nucleus tractus solitarii.
Purification and characterization of FMRFamidelike immunoreactive substances from the lobster nervous system: Isolation and sequence analysis of two closely related peptides
Authors: Trimmer Barry Andrew , Kobierski Linda A. , Kravitz Edward A.
Published: January 2005

In the preceding paper (Kobierski et al: J. Comp. Neurol. 266:1–15, '87) FMRFamidelike immunoreactivity (FLI) was localized to specific cells and processes in the nervous system of the lobster Homarus americanus. In an effort to establish a role for this material we have purified and characterized a variety of immunoreactive peptides that can be extracted from the secretory pericardial organs. By using gel‐filtration chromatography and three different HPLC systems, it has been established that little or no authentic FMRFamide is present. Of the major immunoreactive components two peptides were purified in sufficient quantity for microsequence analysis and have been tentatively identified as the octapeptides Ser‐Asp‐Arg‐Asn‐Phe‐Leu‐Arg‐Phe‐amide (FLI 3) and Thr‐Asn‐Arg‐Asn‐Phe‐Leu‐Arg‐Phe‐amide (FLI 4). Both of these are novel neuropeptides with some sequence homology to the previously described FMRFamide family.

The pericardial organs release FLI when depolarized with 100 mM K+ in the presence of calcium. Between 75 and 80% of this release is accounted for by FLI 3 and FLI 4. One of these peptides (FLI 4) has been synthesized and shown to cochromatograph with the endogenous immunoreactive material. Preliminary studies show that this peptide can act as a modulator of exoskeletal and cardiac neuromuscular junctions.
Segment‐related, mosaic neurogenetic pattern in the forebrain and mesencephalon of early chick embryos: I. Topography of ache‐positive neuroblasts up to stage HH18
Authors: Puelles L. , Amat J. A. , Martinez‐de‐la‐Torre M.
Published: January 2005

Histochemical mapping of AChE‐positive neuroblasts in sectioned and whole‐mounted preparations of the chick embryo mesencephalon and prosencephalon allows a correlation of early neural tube morphogenesis (segmentation, longitudinal compartmentation) with the heterochronic pattern of neurogenesis. One significant finding is that the initial appearance of neuroblasts in the forebrain does not follow neuromeric segmentation, but evolves in parallel with it. Early neuroblasts appear as separate, distinct groups within specific matrix territories at the center of the transverse neuromeric segments. Neighbouring segments display different spatiotemporal patterns of neurogenesis. Overall gradients of differentiation in the rostrocaudal and ventrodorsal directions are absent, whereas a clear‐cut segment‐related, mosaic pattern becomes evident. Notwithstanding this, gross regularities of heterochrony in the neurogenetic behavior of the different segments lead to a definition of elemental longitudinal compartments of the forebrain and mesencephalon (floor, paramedian, basal, and alar regions) on the basis of precocious differentiation of the basal region and retarded differentiation of the paramedian and alar regions.
Functional organization of crayfish abdominal ganglia: II. Sensory afferents and extensor motor neurons
Authors: Leise Esther M. , Hall Wendy M. , Mulloney Brian
Published: January 2005

Abdominal ganglia of crayfish contain identifiable neuropils, commissures, longitudinal tracts, and vertical tracts. To determine the functional significance of this ganglionic framework, we backfilled the following types of neurons with cobalt chloride: sensory hair afferents, slow and fast extensor motor neurons, the segmental stretch receptor neurons, and their inhibitory accessory cells. After the cobalt ions were precipitated and intensified, we studied the central projections of the filled neurons within the ganglionic structures. All of the axons of these neurons exit or enter each of the first five abdominal ganglia through the second pair of nerves.

Our description of the central projections of the hair afferents is the first in the literature. These afferents innervate the large ventral horseshoe neuropil (HN) in the core of each ganglion. This neuropil is homologous to the insect ventral association centers, which also process sensory information. Furthermore, we discovered that some of the crayfish afferents innervate glomeruli within the HN.

The slow and fast extensor motor neurons, the stretch receptor neurons, and the accessory cells branch mostly in the dorsal part of the ganglion. We reinterpret previous identifications of the extensor neurons that were based largely on soma position. Together with our previous descriptions of the flexor motor neurons, these results allow us to relate both rapid tail‐flips and slower postural movements to the structure of the segmental ganglia.
Evidence for centripetally shifting terminals on the tectum of postmetamorphic Rana pipiens
Authors: Hitchcock Peter F. , Easter Stephen S.
Published: January 2005

In larval frogs the retina and tectum grow in topologically dissimilar patterns: new cells are added as peripheral annuli in the retina and as caudal crescents in the tectum. Retinotopy is maintained by the continual caudalward shifting of the terminals of the optic axons. After metamorphosis the pattern of growth changes. The retina continues to add new ganglion cells peripherally, but there is no neurogenesis in the tectum. To maintain retinotopy in postmetamorphic frogs, the terminals of the optic axons must continually shift toward the central tectum.

We tested the proposal of centripetally shifting axons by making punctate injections of horseradish peroxidase (HRP) in the tectum of adult Rana pipiens and observing the patterns of filled cells in the contralateral retina, as was done in the goldfish (Easter and Stuermer, '84). Punctate applications of HRP in the tectum should be taken up: (1) by fascicles, and label a partial anulus of cells, (2) by terminals, and label a cluster of cells in the corresponding retinotopic site, and (3) by the extrafascicular axonal segments, and label a band of cells connecting the partial annulus to the cluster. If the terminals have shifted centripetally, the band of cells labeled through their extrafascicular segments should have a spoke‐like orientation, with the center of the retina as the hub. As the tectal site moves from rostral to caudal, this band of cells should move, pendulum‐like, from temporal to nasal retina.

In general, the patterns of HRP‐filled retinal cells we observed were consistent with our predictions. In addition, HRP taken up by the oldest (rostral) tectal axons produced more complex patterns of filled cells that indicated that these axons had shifted both caudally before metamorphosis and centripetally after.
Trajectories of regenerating retinal axons in the goldfish tectum: I. A comparison of normal and regenerated axons at late regeneration stages
Authors: Stuermer Claudia A. O.
Published: January 2005

To visualize and compare the intratectal path of normal and regenerated retinal axons, HRP was applied to localized sites in the dorsotemporal and dorsonasal retina in normal goldfish and in goldfish at 3–12 months after optic nerve section. The anterogradely labeled axons were traced in tectal whole mounts.

In normal animals the axons were confined to the appropriate ventral hemitectum. Therein they ran in very orderly routes (Stuermer and Easter: J. Neurosci. 4:1045–1051, '84) and terminated in regions retinotopic to the labeled ganglion cells in the retina. The terminal arbors of dorsotemporal axons resided in the ventrocaudal tectum and those of dorsonasal axons in the ventrocaudal tectum.

In regenerating animals the terminal arbors also resided at retinotopic regions, where they sometimes formed two separate clusters. In contrast to normal axons, the regenerating ones traveled in abnormal routes through the appropriate and inappropriate hemitectum. From various ectopic positions, they underwent course corrections to redirect their routes toward the retinotopic target region. In their approach toward their target sites, dorsotemporal and dorsonasal axons behaved differently in that the vast majority of dorsotemporal axons coursed over the more rostral tectum whereas dorsonasal axons progressed into the caudal tectal half.

This differential behavior of regenerating dorsonasal and dorsotemporal axons was substantiated by a quantitative evaluation of axon numbers and orientations.
Neonatal deafening alters nonpyramidal dendrite orientation in auditory cortex: A computer microscope study in the rabbit
Authors: McMullen N. T. , Goldberger B. , Suter C. M. , Glaser E. M.
Published: January 2005

In order to examine the influence of afferent input on nonpyramidal dendrite development in the auditory cortex, unilateral deafening was carried out in neonatal rabbits at birth, approximately 6 days prior to the onset of hearing. Deafening was produced by surgical removal of the incus and stapes ossicles, aspiration of the cochlear perilymph, and kanamycin injection into the oval window. At 60 days of age, acoustic stimulation of the deafened ear was unable to evoke auditory brainstem responses. The brains of experimental and littermate control rabbits were processed according to the Golgi‐Cox Nissl method. The dendritic systems of lamina III/IV spine‐free nonpyramidal cells in the auditory cortex contralateral to the deafened ear were digitized from 340‐μm‐thick coronal sections with the aid of a computer microscope. Three‐dimensional spatial and statistical analyses revealed that nonpyramidal dendrite length in neonatally deafened rabbits increased 27% relative to littermate controls. A fan‐in projection analysis revealed that the increased dendrite length in the deafened animals was maximum in the tangential direction and toward the white matter. Computer rotation of digitized neurons from neonatally deafened rabbits also revealed evidence of abnormal dendritic growth in the form of recurved dendrites. We interpret our results to indicate that unilateral cochlear destruction early in development causes a reorganization of the ascending auditory pathway which extends to the contralateral cerebral cortex. Because the auditory cortex contralateral to the deafened ear still receives acoustic input from the undamaged ipsilateral ear, normal nonpyramidal dendritic growth in the auditory cortex is, in part, dependent upon afferent activity arising from both ears.
Distribution of cells projecting to thalamus vs. Those projecting to cerebellum in subdivisions of the dorsal column nuclei in raccoons
Authors: Ostapoff E.‐Michael , Johnson John Irwin
Published: January 2005

To learn the distribution of cells projecting to the thalamus, as opposed to the cerebellum, in the mechanosensory nuclei of the dorsal medulla of raccoons, we analyzed the retrograde transport of horseradish peroxidase from the ventrobasal complex of the thalamus and from the cerebellum. We found six nuclear regions projecting heavily to the thalamus with very small projections to the cerebellum: Bischoff's, central cuneate, central gracile, rostral cuneate, rostral gracile nuclei, and cell group z. Two regions showed heavy projections to the cerebellum with no projections to the thalamus: the lateral portion of the external cuneate nucleus and the compact portion of cell group x. Four regions showed more equivalent projections to both target regions: basal cuneate, medial portion of the external cuneate nucleus, medial tongue extension of the external cuneate nucleus, and reticular portion of cell group x. Three more ventral regions were labeled: lateral cervical nucleus from thalamic injections but not from cerebellar injections; central cervical nucleus from cerebellar injections, which crossed the mid‐line, but not from thalamic injections; and lateral reticular nucleus from both target regions. In most medullary regions, most cells project to one target and very few project to the other; we suggest that the cells projecting to the minor target convey samples of the information going to the major target.
Medullary sources of projections to the kinesthetic thalamus in raccoons: External and basal cuneate nuclei and cell groups x and z
Authors: Ostapoff E.‐Michael , Johnson John Irwin , Albright Bruce C.
Published: January 2005

In raccoons and other mammals, a pathway for kinesthetic sensation (from muscles, fascia, tendons, and joints) reaches the anterodorsal cap of the ventrobasal thalamus and the anteriormost part of the somatic sensory cerebral cortex. To find the medullary component of this kinesthetic pathway in raccoons, small injections of horseradish peroxidase were made in the thalamus under guidance of simultaneous electrophysiological recording from kinesthetic projections. As determined by retrograde labeling following these injections, kinesthetic thalamic subregions receive projections as follows: caudomedial from cells in the external cuneate nucleus and its medial tongue, rostromedial from cells in basal cuneate nucleus, and rostrolateral from cells in cell group z and the reticular division of cell group x. Electro‐physiological recording showed kinesthetic representations in each of these medullary regions. Labeled cells were also observed in the infratrigeminal subnucleus of the lateral reticular nucleus. Cats have kinesthetic projections to the thalamus from the basal cuneate and cell group z; raccoons (and monkeys) have these plus projections from the external cuneate and cell group x. This suggests that the kinesthetic projection system in raccoons and monkeys is expanded in correlation with their more dextrous use of the hand.
The motor nuclei and sensory neurons of the IIIRD, IVTH, and VITH cranial nerves in the monitor lizard, Varanus exanthematicus
Authors: Barbas‐Henry Heleen A. , Lohman Anthony H. M.
Published: January 2005

The motor nuclei of the oculomotor, trochlear, and abducens nerves of the reptile Varanus exanthematicus and the neurons that subserve the sensory innervation of the extraocular muscles were identified and localized by retrograde and anterograde transport of horseradish peroxidase (HRP). The highly differentiated oculomotor nuclear complex, located dorsomedially in the tegmentum of the midbrain, consists of the accessory oculomotor nucleus and the dorsomedial, dorsolateral, intermediate, and ventral subnuclei. The accessory oculomotor nucleus projects ipsilaterally to the ciliary ganglion. The dorsomedial, dorsolateral, and intermediate subnuclei distribute their axons to the ipsilateral orbit, whereas the ventral subnucleus, which innervates the superior rectus muscle, has a bilateral, though predominantly contralateral projection.

The trochlear nucleus, which rostrally overlaps the oculomotor nuclear complex, is for the greater part a comma‐shaped cell group situated lateral, dorsal, and medial to the medial longitudinal fasciculus. Following HRP application to the trochlear nerve, almost all retrogradely labeled cells were found in the contralateral nucleus. The nuclear complex of the abducens nerve consists of the principal and accessory abducens nuclei, both of which project ipsilaterally. The principal abducens nucleus is located just beneath the fourth ventricle laterally adjacent to the medial longitudinal fasciculus and innervates the posterior rectus muscle. The accessory abducens nucleus has a ventrolateral position in the brainstem in close approximation to the ophthalmic fibers of the descending trigeminal tract. It innervates the retractor bulbi and bursalis muscles. The fibers arising in the accessory abducens muscles form a loop in or just beneath the principal abducens nucleus before they join the abducens nerve root.

The afferent fibers conveying sensory information from the extraocular muscles course in the oculomotor nerve and have their perikarya in the ipsilateral trigeminal ganglion, almost exclusively in its ophthalmic portion.
Enigmatic bipolar cell of rat visual cortex
Authors: Peters Alan , Harriman Katherine M.
Published: January 2005

Our earlier Golgi‐electron microscopic study of bipolar cells in the rat visual cortex showed the axons of these neurons as forming asymmetric synapses (Peters and Kimerer; J. Neurocytol, 10:921–946, '81) in which the most common postsynaptic elements were dendritic spines. This result was unexpected, since Parnavelas (Parnavelas, Sullivan, Lieberman, and Webster: Cell Tissue Res. 183:499–517, '77) had earlier shown a bipolar cell from the same cortex to have an axon forming symmetric synapses with dendritic shafts. Here then was an enigma, strengthened by examination of neuronal components labelled by antibodies to two compounds in particular—namely, vasoactive intestinal polypeptide (VIP) and choline acetyltransferase (ChAT). Antibodies to these compounds preferentially label bipolar cells in the rat cerebral cortex, and the labelled axon terminals form symmetric synapses.

Against this background the present study was performed, and it has been shown that the resolution to the enigma is that there are two different populations of bipolar cells in the rat visual cortex. Thus some Golgi‐impregnated bipolar cells examined by electron microscopy after gold toning have been found to possess axons forming asymmetric synapses, and others have been found to have axons forming symmetric synapses, The axons of the bipolar cells forming asymmetric synapses most commonly synapse with dendritic spines (67%), although other terminals synapse with dendritic shafts (33%). In contrast, the bipolar cells with axons forming symmetric synapses preferentially synapse with dendritic shafts (100%). The population of bipolar cells that form symmetric synapses includes the ones that label with antibodies to vasoactive intestinal polypeptide (VIP), for the axons of VIP‐labelled bipolar cells have been traced to labelled terminals forming symmetric synapses. However, examination of the population of VIP‐labelled axon terminals shows that in addition to dendritic shafts, some of the labelled terminals synapse with the cell bodies of pyramidal and nonpyramidal cells, This includes bipolar cells, some of which receive large numbers of VIP‐labelled axon terminals. It is also shown that some VIP‐positive bipolar cells have myelinated axons. Analysis of tissue labelled with VIP antibody reveals that about 50% of the total population of bipolar cells in the rat visual cortex is VIP positive. These results are discussed in the light of information about labelling of bipolar cells with antibodies to γ‐aminobutyric acid (GABA) and to other peptides, and it is suggested that most VIP‐positive bipolar cells also contain GABA.