bluuebunny/crossref_metadata_2025 huggingface dataset:
Early development of cerebellar afferent systems that contain corticotropin‐releasing factor
Authors: Cummings Sharon L. , Young W. Scott , King James S.
Published: January 2005

Corticotropin‐releasing factor (CRF) and CRF binding sites have been described in the cerebellum of several species, including the North American opossum (Didelphis marsupialis virginiana), the species used in the present study. Iontophoretic application of this peptide in the adult cerebellum enhances the spontaneous and amino acid‐induced firing rate of Purkinje cells and overcomes the GABA‐induced suppression of Purkinje cell activity. The present account provides immunohistochemical evidence for the localization of CRF in the North American opossum within developing axons and their growth cones prior to the formation of the Purkinje cell and granule cell layers. CRF mRNA is present on postnatal day (PD) 1 within the internal migratory stream of the ventral lateral medulla, which contains migrating olivary neurons, and within the ventral medulla in the region, where inferior olivary neurons first aggregate to form the inferior olivary complex. The olivary complex can first be identified on PD2 and is well defined by PD3. CRF‐immunoreactive axons are evident within the cerebellar primordium on PD4 and penetrate the nascent Purkinje cell layer between PD14 and PD26. By PD26, CRF‐immunoreactive puncta are organized within the Purkinje cell layer as parasagittal bands. Thus, olivary neurons express CRF mRNA prior to the time that the first CRF‐labeled axons are present in the cerebellar anlage (PD4), suggesting that olivary axons are among the first to reach the developing cerebellum. Coincident (PD1–3) with the early transcription of CRF mRNA in the inferior olive, cells in the medullary reticular formation (PD1) and locus coeruleus (PD2) also transcribe CRF mRNA. These brainstem sites also could provide CRF‐immunoreactive axons to the developing cerebellum; however, based on the results of this study and correlative data reported in the literature, we propose that the primary source of early‐arriving CRF fibers is the inferior olivary complex. The early arrival of CRF‐containing axons in the cerebellum prior to synaptogenesis and migration of both granule cells and Purkinje cells suggests a role for this peptide in target recognition and synaptic organization. © 1994 Wiley‐Liss, Inc.
TrkA‐immunoreactive profiles in the central nervous system: Colocalization with neurons containing p75 nerve growth factor receptor, choline acetyltransferase, and serotonin
Authors: Sobreviela Teresa , Clary Douglas O. , Reichardt Louis F. , Brandabur Melanie M. , Kordower Jeffrey H. , Mufson Elliott J.
Published: January 2005

The present investigation used an antibody directed against the extracellular domain of the signal transducing nerve growth factor recepto, trkA, to reveal immunoreactive perikarya or fibers within the olfactory bulb and tubercle, cingulate cortex, nucleus accumbens, striatum, endopiriform nucleus, septal/diagonal band complex, nucleus basalis, hippocampal complex, thalamic paraventricular and reuniens nuclei, periventricular hypothalamus, interpeduncular nucleus, mesencephalic nucleus of the fifth nerve, dorsal nucleus of the lateral lemniscus, prepositus hypoglossal nucleus, ventral cochlear nucleus, ventral lateral tegmentum, medial vestibular nucleus, spinal trigeminal nucleus oralis, nucleus of the solitary tract, raphe nuclei, and spinal cord. Colocalization experiments revealed that virtually all striatal trk‐Aimmunoreactive neurons (> 99%) coexpressed choline acetyltransferase (ChAT) but not p75 nerve growth factor receptor (NGFR). Within the septal/diagonal band complex virtually all trkA neurons (> 95%) coexpressed both ChAT and p75 NGFR. More caudally, dual stained sections revealed numerous trkA/ChAT (> 80%) and trkA/p75 NGFR (> 95%) immunoreactive neurons within the nucleus basalis. In the brainstem, raphe serotonergic neurons (45%) coexpressed trkA. Sections stained with a pan‐trk antibody that recognizes primarily trkA, as well as trkB and trkC, labeled neurons within all of these regions as well as within the hypothalamic arcuate, supramammilary, and supraoptic nuclei, hippocampus, inferior and superior colliculus, substantia nigra, ventral tegmental area of T'sai, and cerebellar Purkinje cells. Virtually all of these other regions with the exception of the cerebellum also expressed pan‐trk immunoreactivity in the monkey. The widespread expression of trkA throughout the central neural axis suggests that this receptor may play a role in signal transduction mechanisms linked to NGF‐related substances in cholinergic basal forebrain and noncholinergic systems. These findings suggest that pharmacological use of ligands for trkA could have beneficial effects on the multiple neuronal systems that are affected in such disorders as Alzheimer's disease. © 1994 Wiley‐Liss, Inc.
Neurotrophin receptor mRNA expression defines distinct populations of neurons in rat dorsal root ganglia
Authors: Wright D. E. , Snider W. D.
Published: January 2005

The biological actions of neurotrophins are mediated by specific neurotrophin receptor tyrosine kinases (Trks). A low‐affinity nerve growth factor (NGF) receptor, p75, appears to modulate sensitivity to neurotrophins in some neuronal populations. It has been recently demonstrated that genes encoding members of the Trk family are expressed in distinct patterns in the dorsal root ganglia DRG; Mu et al. [1993] (J. Neurosci. 13:4029–4041). However, the extent to which different neurotrophin receptor genes are coexpressed by individual DRG neurons is unknown. The question of coexpression is important since the expression of more than one member of the trk family by DRG neurons would suggest the potential for regulation by multiple neurotrophins. To address this question, a combination of isotopic and colorimetric in situ hybridization was performed on rat thoracic DRG using riboprobes specific for trk A, trkB, trkC, and p75. We show here that neurons that express trkA are largely distinct from those that express trkC, although there is a small subpopulation that expresses both of these genes. We also show that there is a distinct population of DRG neurons that expresses trkB and does not coexpress either trkA or trkC. P75 is expressed in almost all neurons that express trkA or trkB, but is coexpress in only 50% of trkC‐expressing neurons. Importantly, p75 is not expressed in DRG neurons independent of trk expression. Finally, a subpopulation of DRG neurons does not express any of the neurotrophin receptor mRNAs.

Our results demonstrate that there are distinct populations of DRG neurons that express each member of the neurotrophin receptor tyrosine kinase family. Our findings of extensive colocalization of p75 with trkA and trkB lend support to the idea that p75 is important in mediating the actions of NGF and brain‐derived neurotrophic factor on DRG neurons. Interestingly, however, p75 expression is clearly unimportant for a subpopulation of neurons that require neurotrophin‐3. The fact that p75 is not expressed in the absence of trkA, trkB, or trkC suggests that the function of p75 is closely related to functions of the known neurotrophin receptor tyrosine kinases. Finally, our results suggest that a significant percentage of DRG neurons may be regulated by non‐neurotrophin neuronal growth factors. © 1995 Willy‐Liss, Inc.
Lack of topography in the spinal cord projection of the rabbit soleus muscle
Authors: Cramer Karina S. , van Essen David C.
Published: January 2005

Several mammalian muscles in the limb and trunk receive topographically organized innervation from spinal cord motor neurons. Some muscles in which topographic innervation has been demonstrated have a sheet‐like architecture; others are compartmentalized and/or have more than one origin. An interesting question is whether topography is related to these anatomical features, or whether it occurs as a general consequence of the development of innervation.

To address this question, we examined the pattern of projections to the soleus muscles, which lacks these anatomical features. Intracellular recordings of endplate potentials in early and intermediate age rabbits were used to assess the spinal origin of inputes to two distinct regions of the muscle. Both regions were innervated by both rostral and caudal portions of the motor pool. These experiments also showed that individual muscle fibers frequently receive separate inputs arising from widely separated regions of the motor pool. In another set of experiments, physiological measurements of tension overlap in young, polyinnervated muscles showed that the relative positions of motor neurons in the spinal cord do not correlate with the extent to which motor units share muscle fibers. In a third set of experiments, motor neurons were retrogradely labeled following local injections of tracer into muscle. Small and large local injections resulted in comparably dispersed labeling of motor neurons within the motor pool. Moreover, the rostrocaudal position of labeled neurons was not correlated with the position of the injection site within the muscle. Together, these results provide evidence that the soleus muscle is not topographically innervated. Furthermore, an examination of several age groups suggests that the innervation pattern in this muscle is not altered by postnatal synapse elimination. © 1995 Willy‐Liss, Inc.
Structure and innervation of the sensory organs on the snout of the star‐nosed mole
Authors: Catania Kenneth C.
Published: January 2005

The star‐nosed mole possesses a conspicuous specialization of its snout in the form of 22 fleshy appendages that fan out from around the nostrils. These appendages are used by the mole to explore its underground environment and are repeatedly brought into contact with objects of interest to the mole. This report describes the structure, innervation, and distribution of the sensory organs on the star of the star‐nosed mole and briefly describes the behavioral use of the star. Each of the 22 appendages of the star is covered with a continuous array of Eimer's organs. These sensory receptors are modifications of the epidermal surface that take the form of bulbous papillae. Each Eimer's organ contains a column or stack of epidermal cells accompanied by nerve processes that originate from myelinated fibers in the underlying dermis. These neural processes travel through the cell column and form terminal swellings just below the outer layer of keratinized epidermis. Each Eimer's organ also contains a single Merkel cell‐neurite complex within the cell column and a single lamellated corpuscle immediately below the cell column in the connective tissue of the dermis. There are approximately 30,000 Eimer's organs on the snout of this mammal, making this structure perhaps the most sensitive tactile organ yet discovered for its size. The segregation of these organs to individual appendages, not unlike the fingers of primates. affords an intriguing model for the study of somatosensory systems in mammals. © 1995 Willy‐Liss, Inc.
Neurofilament protein defines regional patterns of cortical organization in the macaque monkey visual system: A quantitative immunohistochemical analysis
Authors: Hof Patrick R. , Morrison John H.
Published: January 2005

Visual function in monkeys is subserved at the cortical level by a large number of areas defined by their specific physiological properties and connectivity patterns, For most of these cortical fields, a precise index of their degree of anatomical specialization has not yet been defined, although many regional patterns have been described using Nissl or myelin stains. In the present study, an attempt has been made to elucidate the regional characteristics, and to varying degrees boundaries, of several visual cortical areas in the macaque monkey using an antibody to neurofilament protein (SM132). This antibody labels a subset of pyramidal neurons with highly specific regional and laminar distribution patterns in the cerebral cortex. Based on the staining patterns and regional quantitative analysis, as many as 28 cortical fields were reliably identified. Each field had a homogeneous distribution of labeled neurons, except area V1, where increases in layer IVB cell and in Meynert cell counts paralleled the increase in the degree of eccentricity in the visual field representation. Within the occipitotemporal pathway, areas V3 and V4 and fields in the inferior temporal cortex were characterized by a distinct population of neurofilament‐rich neurons in layers II–IIIa, whereas areas located in the parietal cortex and part of the occipitoparietal pathway had a consistent population of large labeled neurons in layer Va. The mediotemporal areas MT and MST displayed a distinct population of densely labeled neurons in layer VI. Quantitative analysis of the laminar distribution of the labeled neurons demonstrated that the visual cortical areas could be grouped in four hierarchical levels based on the ratio of neuron counts between infragranular and supragranular layers, with the first (areas V1, V2, V3, and V3A) and third (temporal and parietal regions) levels characterized by low ratios and the second (areas MT, MST, and V4) and fourth (frontal regions) levels characterized by high to very high ratios. Such density trends may correspond to differential representation of corticocortically (and corticosubcortically) projecting neurons at several functional steps in the integration of the visual stimuli. In this context, it is possible that neurofilament protein is crucial for the unique capacity of certain subsets of neurons to perform the highly precise mapping functions of the monkey visual system. © 1995 Wiley‐Liss, Inc.
Birth dates and survival after axotomy of neurochemically defined subsets of trigeminal ganglion cells
Authors: White Fletcher A. , Chiaia Nicolas L. , Macdonald Gordon J. , Rhoades Robert W.
Published: January 2005

Trigeminal (V) ganglion cells with different neurochemical phenotypes or different birth dates are affected differently by neonatal axonal transection. The aim of the present study was to determine if V ganglion cell birth date and neurochemical phenotype were correlated and if these two variables could be related to responses to neonatal axonal transection. Immunocytochemistry, histochemistry, and [3H] thymidine labelling were used to determine the birth dates of V ganglion cells recognized by antibodies directed against neurofilament protein (NF), calcitonin gene‐related peptide (CGRP), and substance P (SP) and those that bound the lectin Bandierea simplicifolia‐I (BS‐I). All V ganglion cells were born between embryonic days (E‐) 9.5 and 14.5. All ganglion cells were born between E‐9.5 and E‐14.5. In a normalized population (percentages normalized to equal 100%), over 90% of NF‐positive V ganglion cells were born between E‐10.5 and E‐12.5. The majority of CGRP‐positive and SP‐positive ganglion cells (> 90%) were generated from E‐13.5 to E‐14.5 and E‐12.5 through E‐14.5, respectively. Almost 85% of BS‐I‐positive ganglion cells were generated on E‐12.5 through E‐14.5. Previous results and additional data from this study indicated that NF‐ and BS‐I‐positive ganglion cells are proportionally more likely to be lost after neonatal axotomy and that SP‐positive cells are more likely to remain. The percentage of CGRP‐positive cells in the V ganglion was not significantly altered by neonatal infraorbital nerve transection. Overall, these findings do not indicate a strong relationship between cell birth date and the probability of survival after neonatal axonal damage for all V ganglion cell phenotypes. © 1995 Wiley‐Liss, Inc.
Sex differences in the number of synaptic junctions in the binocular area of the rat visual cortex
Authors: Reid Silvia N. M. , Juraska Janice M.
Published: January 2005

We had found that the binocular area of the visual cortex is larger in volume and has more neurons in male than in female rats. The present study examined whether the number of synaptic junctions in this area is sexually dimorphic. Ten littermate pairs of 90‐day‐old (socially housed) Long‐Evans hooded rats were used. Synaptic junctions were counted and their lengths were measured on electron micrographs taken from layers II–III of the binocular visual cortex. There were no sex differences in the numerical density of synaptic junctions, the number of synaptic junctions per neuron, or the length of synaptic junctions within any synaptic category or of all synapses combined. Sex differences were found in the total number of synaptic junctions and in several categories (asymmetric synapses, spine synapses, asymmetric spine synapses): male rats had more synaptic junctions than female rats because of the larger volume of layers II‐‐III in the binocular area of male rats. These data indicate that neurons in the binocular visual cortex of both male and female rats receive a characteristic number of synaptic junctions, but the greater number of neurons in the binocular area of male rats results in more synaptic junctions in the area. © 1995 Wiley‐Liss, Inc.
Correlation of axon frojections anct peptide immunoreactivity in mesocerebral neurons of the snail helix aspersa
Authors: Ll Guoyi , Chase Ronald
Published: January 2005

The purpose of this investigation was to elucidate the organization of efferent neurons in the mesocerebrum of a terrestrial snail. The mesocerebrum is one of three regions, or lobes, that can be identified by gross inspection. Previous studies have indicated a possible function for the mesocerebrum in the control of mating behavior. We used both anterograde and retrograde tracing methods to determine the axon projections of mesocerebral neurons. Virtually all the neurons (96%) send an axon into the cerebropedal connective nerve, and about 25% of these fibers continue into the nervus cutaneus pedalis primus dexter, which innervates the dart sac. Many neurons have additional axon branches in other perves, especially the penial nerve, which receives projections from about 25% of mesocerebral cells. Neurons that are backfilled from the nervus cutaneus pedalis primus dexter are predominately immunoreactive for FMRFamide, whereas neurons that are backfilled from the penial nerve are predominately immunoreactive for APGWamide. These results suggest a functional association between FMRFamide and dart shooting on the one hand, and between APGWamide and penial eversion on the other. Some cells contain both APGWamide and FMRFamide; these cells, may have dual projections in both the penial nerve and the nervus cutaneus pedalis primus dexter. © 1995 Wiley‐Liss, Inc.
Distribution of neurotensin‐containing neurons in the central nervous system of the dog
Authors: Atoji Yasuro , Watanabe Hideki , Yamamoto Yoshio , Suzuki Yoshitaka
Published: January 2005

The distribution of neurotensin‐containing cell bodies and fibers was examined in the central nervous system of the dog using light microscopic immunohistochemistry. A very large population of neurotensin‐containing cell bodies was observed in the septal nuclei, nucleus accumbens septi, preoptic areas, bed nucleus of the stria terminalis, olfactory tubercle, entorhinal cortex, ventral subiculum, anterodorsal thalamic nucleus, anteroventral thalamic nucleus, nucleus reuniens, lateral habenular nucleus, parabrachial nucleus, and nucleus of the solitary tract. Extremely dense networks of neurotensin‐containing fibers were found in the globus pallidus, hypothalamus, infundibular stalk, ventral tegmental area, periaqueductal gray, interpeduncular nucleus, and spinal nucleus of the trigeminal nerve and substantia gelatinosa. However, the cerebral neocortex and cerebellum were negative for neurotensin in the present study. When the present findings are compared with those in other animals, it is clear that the major species‐specific differences in distribution involve three immunonegative regions and four immunopositive regions in the dog: The former are the cerebral neocortex, mammillary body, and hippocampus; the latter are the cell bodies in the pyramidal layer of the olfactory tubercle, the superficial and middle layers of the entorhinal cortex and ventral subiculum, and the nerve fibers in the interpeduncular nucleus. The present study indicates a rather extensive network of neurotensin neurons in the central nervous system of the dog. © 1995 Wiley‐Liss, Inc.
Proliferation zones in the brain of adult gymnotiform fish: A quantitative mapping study
Authors: Zupanc Günther K. H. , Horschke Ingrid
Published: January 2005

Whereas in mammals postnatal neurogenesis, gliogenesis, and angiogenesis appear to be kept at low rates, in fish the capability for the production of new brain cells during adulthood is very pronounced. Many of the newly generated cells originate from germinal layers that maintain their proliferative activity during adulthood. By employing incorporation of the thymidine analogue 5‐bromo‐2′‐deoxyuridine (BrdU) into mitotic active cells, we have quantitatively mapped such proliferation zones in the brain of adult Apteronotus leptorhynchus (Gymnotiformes, Teleostei).

In the telencephalon, diencephalon, mesencephalon, and rhombencephalon, the total number of BrdU‐labelled cells was low, making up approximately 25% of all mitotic active cells in the brain. Many of these cells were scattered over wide areas. Otherwise, zones of high proliferative activity were typically located at or near the surface of ventricular, paraventricular, and cisternal systems. Approximately 75% of all BrdU‐labelled cells found in the brain of adult Apteronotus leptorhynchus were situated in the cerebellum. Zones displaying proliferative activity were restricted to small areas, such as narrow stripes around the midline of corpus cerebelli and valvula cerebelli, the boundary between corpus and valvula, and a large portion of the area covered by the eminentia granularis medialis.

Counts indicate that, on average, 100,000 cells, corresponding to approximately 0.2% of the total population of cells in the brain of adult Apteronotus leptorhynchus, are in S‐phase within a period of 2 hours. At least part of these newly generated cells is added to the population of already existing cells. This leads to a permanent growth of the brain with increasing size of the fish, a process that appears to slow down only in individuals of relatively advanced age. © 1995 Wiley‐Liss, Inc.
Projections from the central cervical nucleus to the cerebellar nuclei in the rat, studied by anterograde axonal tracing
Authors: Matsushita Matsuo , Yaginuma Hiroyuki
Published: January 2005

Projections from the central cervical nucleus (CCN) to the cerebellar nuclei were examined following injections of Phaseolus vulgaris‐leucoagglutinin or cholera toxin subunit B into the C1–C3 segments in the rat. Labeled axons and terminals were immunohistochemically demonstrated. Labeled spinocerebellar fibers arising from the CCN entered the cerebellum through the inferior and the superior cerebellar peduncles. Labeled mossy fiber terminals were seen in lobules I–VI, sublobule VIIb, lobules VIII and IX, and the copula pyramidis of the cerebellar cortex. Labeled axons ran toward the cerebellar cortex, through and between the medial and the interpositus nuclei, and gave off collateral axons and terminal axons to the cerebellar nuclei. The projections to the cerebellar nuclei were predominantly contralateral to the cells of origin. Labeled terminals were distributed from the medial to the ventrolateral part of the middle subdivision of the medial nucleus throughout its rostrocaudal extent. Labeled terminals were also seen in the lateral part of the medial nucleus and in the border region between the medial nucleus and the interpositus nuclei, which corresponds to the rostromedial extension of the posterior interpositus nucleus. In the anterior interpositus nucleus, labeled terminals were distributed dorsoventrally in the middle third of the mediolateral extent. They were more numerous in the rostrodorsal part of this area. Labeled terminals were distributed dorsally and caudally in the medial third of the posterior interpositus nucleus. No labeled terminals were seen in the caudomedial subdivision and the dorsolateral protuberance of the medial nucleus, the dorsolateral hump region and the lateral nucleus. The present study demonstrates that the CCN projects to specific areas of the cerebellar cortex and the medial and the interpositus nuclei. © 1995 Wiley‐Liss, Inc.
Serotonin inputs to rabbit sympathetic preganglionic neurons projecting to the superior cervical ganglion or adrenal medulla
Authors: Jensen Iwona , Llewellyn‐Smith Ida J. , Pilowsky Paul , Minson Jane B. , Chalmers John
Published: January 2005

The input from serotonin‐containing nerve fibres to rabbit sympathetic preganglionic neurons projecting to either the superior cervical ganglion or the adrenal medulla was investigated by combining retrograde tracing with the B subunit of cholera toxin and immunocytochemistry for serotonin. There were pronounced rostrocaudal variations in the density of serotonin fibres in the rabbit intermediolateral cell column from T1 to L4; maximum numbers of fibres were found in T3‐6 and L3–4 and minimum numbers in T1 and T10–12. By light microscopy, retrogradely labelled sympathetic preganglionic neurons projecting to the superior cervical ganglion or the adrenal medulla received variable densities of close appositions from serotonin‐immunoreactive fibres. Some neurons from each population received many close appositions, whereas others received moderate numbers or few appositions. Appositions occurred on the cell bodies, dendrites, and occasionally axons of sympathetic preganglionic neurons. Rare neurons in both groups of retrogradely labelled cells received no appositions from serotonin‐containing nerve fibres. At the ultrastructural level, synapses were found between serotonin‐positive boutons and sympathetic preganglionic neurons projecting either to the superior cervical ganglion or to the adrenal medulla. These results indicate that, through direct synaptic contacts, serotonin‐immunoreactive, presumably bulbospinal, nerve fibres affect the activity of the vast majority of sympathetic preganglionic neurons that send axons either to the superior cervical ganglion or to the adrenal medulla. This serotonin input may be sympathoexcitatory and could mediate increases in sympathetic nerve activity and in the release of catecholamines from the adrenal medulla. © 1995 Wiley‐Liss, Inc.
Topographic organization ot spinal ana trigeminal somatosensory pathways to the rat parabrachial and Kölliker—fuse nuclei
Authors: Feil Karsten , Herbert Horst
Published: January 2005

We examined the organization of somatosensory projections to the parabrachial (PB) and Kölliker‐Fuse (KF) nuclei by employing the retrograde and anterograde axonal transport of Fluorogold and Phaseolus vulgaris–leucoagglutinin (PHA‐L), respectively. Small PHA‐L injections were made into different parts of the spinal trigeminal complex, including the paratrigeminal nucleus, and into different segments and laminae of the spinal dorsal horn. The subnuclear distribution of axonal labeling in the PB and KF was mapped with a camera lucida.

Our results show that the somatosensory input to the PB and KF is highly organized. Neurons in the spinal trigeminal nuclei project predominantly to the KF and to the ventral portion of the external lateral PB. Neurons in the paratrigeminal nucleus project to the ventral lateral P13, the external medial PB, and to caudal aspects of the medial PB. These findings were supported by retrograde tracing experiments with Fluorogold. Spinal cord neurons located in the superficial dorsal horn (laminae I‐II) of upper cervical segments project specifically to the ventral portion of the external lateral PB and, although more sparsely, to various other lateral PB nuclei. In contrast, neurons in the superficial dorsal horn of thoracic and lumbar spinal segments project mainly to the dorsal lateral and the central lateral PB. Finally, neurons in the lateral reticulated area and the lateral spinal nucleus of all spinal segments project almost exclusively to the internal lateral PB, whereas neurons in the respective nuclei of upper cervical segments also project to the KF.

From our data we conclude that the somatosensory projections to the PB and KF are topographically organized. It is assumed that these pathways, which run from trigeminal and spinal neurons through the PB and KF to various forebrain, medullary, and spinal nuclei, form functionally different neural circuits that are involved in somatoautonomic processing. © 1995 Wiley‐Liss, Inc.
GABAAReceptor subunits have differential distributions in the rat retinae: In situ hybridization and immunohistochemistry
Authors: Greferath U. , Grünert U. , Fritschy J. M. , Stephenson A. , Möhler H. , Wässle H.
Published: January 2005

The distributions of nine different subunits of the gamma‐aminobutyric acidA(GABAA) receptor (α1, α2, α3,5; β1, β2, β3; γ2; δ) were investigated in the rat retina using immunocytochemistry and in situ hybridization. With the exception of the α5subunit, all subunits could be localized. Each subunit was expressed in characteristic strata within the inner plexiform layer (IPL). Some subunits (e.g., γ2) showed a ubiquitous distribution, while others (e.g., δ) were restricted to narrow sublayers. Double labeling experiments using different combinations of the subunit‐specific antibodies revealed colocalizations of subunits within individual neurons. Additionally, GABAAreceptor subunits were mapped to distinct populations of retinal neurons by coapplication of defined immunocytochemical markers and subunit‐specific antibodies. Cholinergic amacrine cells were found to express the α2, β1, β2/3and δ subunits, while dopaminergic amacrine cells express the α2, α3and γ2subunits. Dissociated rod bipolar cells express the γ2subunits. In summary, this study provides evidence for the existence of multiple GABAAreceptor subtypes in the retina. The distinct stratification pattern of the subunits in the IPL suggests that different functional circuits involve specific subtypes of GABAA receptors. © 1995 Wiley‐Liss, Inc.
Organization of thalamic projections to the ventral striatum in the primate
Authors: Giménez‐Amaya José Manuel , McFarland Nikolaus R. , De Las Heras Silvano , Haber Suzanne N.
Published: January 2005

Although thalamic projections to the dorsal striatum are well described in primates and other species, little is known about thalamic projections to the ventral or “limbic” striatum in the primate. This study explores the organization of the thalamic projections to the ventral striatum in the primate brain by means of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) and Lucifer yellow (LY) retrograde tracer techniques. In addition, because functional and connective differences have been described for the core and shell components of the nucleus accumbens in the rat and are thought to be similar in the primate, this study also explores whether these regions of the nucleus accumbens can be distinguished by their thalamic input. Tracer injections are placed in different portions of the ventral striatum, including the medial and lateral regions of the ventral striatum; the central region of the ventral striatum, including the dorsal part of the core of the nucleus accumbens; and the shell region of the nucleus accumbens. Retrogradely labeled neurons are located mainly in the midline nuclear group (anterior and posterior paraventricular, paratenial, rhomboid, and reuniens thalamic nuclei) and in the parafascicular thalamic nucleus. Additional labeled cells are found in other portions of the intralaminar nuclear group as well as in other thalamic nuclei in the ventral, anterior, medial, lateral, and posterior thalamic nuclear groups. The distribution of labeled cells varies depending on the area of the ventral striatum injected. All regions of the ventral striatum receive strong projections from the midline thalamic nuclei and from the parafascicular nucleus. In addition, the medial region of the ventral striatum receives numerous projections from the central superior lateral nucleus, the magnocellular subdivision of the ventral anterior nucleus, and parts of the mediodorsal nucleus. After injection into the lateral region of the ventral striatum, few labeled neurons are seen scattered in nuclei of the intralaminar and ventral thalamic groups and occasional labeled cells in the mediodorsal nucleus. The central region of the ventral striatum, including the dorsal part of the core of the nucleus accumbens, receives a limited projection from the midline thqlamic, predominantly from the rhomboid nucleus. It receives much smaller projections from the central medial nucleus and the ventral, anterior, and medial thalamic groups. The shell of the nucleus accumbens receives the most limited projection from the thalamus and is innervated almost exclusively by the midline thalamic nuclei and the central medial and parafascicular nuclei. The shell is distinguished from the rest of the ventral striatum in that it receives the fewest projections from the ventral, anterior, medial, and lateral thalamic nuclei. © 1995 Wiley‐Liss, Inc.
Development of basal forebrain projections to visual cortex: Dil studies in rat
Authors: Calarco Christopher A. , Robertson Richard T.
Published: January 2005

We performed experiments using retrograde and anterograde labeling with DiI to examine the development of basal forebrain (BFB) projections to the visual cortex in postnatal rats. DiI placed in occipital cortex led to retrograde labeling of BFB neurons as early as postnatal day 0 (P0); labeled cells were found mainly in the diagonal band complex but also in the medial septum, globus pallidus, and substantia innominata. The retrogradely labeled BFB cells displayed remarkably well‐developed dendritic arbors, even in younger animals, and showed increases in soma size, dendritic arbors, and dendritic spines over the first 2 postnatal weeks.

Dil placements in the diagonal band led to anterogradely labeled axons in cortex. At early ages (P0–P1), labeled axons were largely confined to white matter. With increasing age, greater numbers of labeled axons were seen in the white matter and in deep cortical layers, and labeled axons extended into superficial layers. The leading edge of labeled fibers reached layer V of visual cortex by P2 and layer IV by P4 and were found throughout the cortical layers by P6. Numbers and densities of labeled axons in visual cortex were greater in older animals, at least through P14.

The time of ingrowth of labeled BFB axons into visual cortex indicates that these afferents grow into particular cortical layers after those layers have differentiated from the cortical plate. These data indicate that basal forebrain projections arrive in occipital cortex after cortical lamination is well underway and after the entry of primary thalamocortical projections. © 1995 Wiley‐Liss, Inc.
Morphology of individual axons projecting from area V2 to MT in the macaque
Authors: Rockland Kathleen S.
Published: January 2005

Efferent axons from area V2 to the middle temporal area (MT) were anterogradely labeled by Phaseolus vulgaris ‐leucoagglutinin (PHA‐L) or biocytin and analyzed in serial reconstructions. Five of seven reconstructed axons had three arbors (each < 200 μm in diameter) in layers 3–4, separated by 200–600 jLm. Two axons terminated in what was apparently a single focus in layers 3–4. Of 15 additional single arbors analyzed, 12 were concentrated in layers 3–4, and measured 200–250 μm across at their widest point. Three of these arbors were more columnar in shape (about 400 μm in diameter), and extended from layer 4 toward layer 1. This system differs in several features from MT‐projecting axons originating from V1. Namely, V2 axons terminating in MT are thinner (∼ 1. 0 μm vs. 3. 0 gm), their terminal specializations are more delicate, and their arbors are concentrated in layer 4 and overlying layer 3, with no collaterals to layer 6. These differences may reflect the distinctive neuronal populations giving rise to these two connectional systems (different sizes of pyramidal neurons in layer 3 of V2, and a mix of pyramidal and spiny stellate cells in area V). Differences may have implications for timing factors; that is, impulses from V1, subserved by large‐caliber axons, may arrive in MT coincidentally with indirect connections via V2 to MT. Another consideration may be the functional architecture of MT. Regularly spaced clusters of neurons have been described in MT which have similar directionality preferences. The interarbor spacing of cortical efferents is consistent with a columnar organization, but the laminar specificity may indicate recruitment of different combinations of postsynaptic populations by V1 or V2 terminations.
Multiple gonadotropin‐releasing hormone (GnRH)‐immunoreactive systems in the brain of the dwarf gourami,Colisa lalia: Immunohistochemistry and radioimmunoassay
Authors: Yamamoto Naoyuki , Oka Yoshitaka , Amano Masafumi , Aida Katsumi , Hasegawa Yoshihisa , Kawashima Seiichiro
Published: January 2005

The present study characterizes gonadotropin‐releasing hormone (GnRH) neuronal groups that are located in several different brain regions by investigating GnRH molecular species and projection patterns in an anabantid fish, Colisa lalia. First, we examined the molecular species of GnRHs in extracts of the brain and the pituitary by reverse‐phase high‐performance liquid chromatography followed by radioimmunoassays. We found salmon GnRH (sGnRH), chicken GnRH‐II (cGnRH‐II), and an unfamiliar GnRH‐like substance.

Next, to examine the distribution of each GnRH molecule in different GnRH neuronal groups, we performed immunohistochemistry using four kinds of antisera and an antibody. Furthermore, we performed brain lesioning experiments of terminal nerve (TN) cells, the most conspicuous GnRH‐immunoreactive cells in Colisa lalia. Comparisons of immunoreactive structures between TN‐lesioned fish and untreated fish elucidated the projection area of each neuronal group. Three major neuronal groups were observed. TN‐GnRH cells, which are located in the transitional area between the olfactory bulb and the telencephalon, showed strong sGnRH and weaker cGnRH‐II immunoreactivity. TN‐GnRH cells projected to wide areas of the central nervous system from the olfactory bulb to the spinal cord. The second group, located in the preoptic area, showed only sGnRH immunoreactivity and projected only to the pituitary. The third ond, located in the midbrain tegmentum, exhibited strong cGnRH‐II and weaker sGnRH immunoreactivity. This cell group projected mainly to brain regions posterior to the hypothalamus and the spinal cord. These different projection patterns suggest functional differentiation of each GnRH neuronal group.
Development of branchiomeric and lateral line nerves in the axolotl
Authors: Northcutt R. Glenn , Brändle Kurt
Published: January 2005

The differentiation of neural crest and ectodermal placodes was examined in the axolotl in order to clarify the contribution of these tissues to the formation of the sensory ganglia of the branchiomeric and lateral line cranial nerves in salamanders. The most rostral branchiomeric nerves, the profundal and trigeminal nerves, appear to arise solely from an ectodermal placode and from neural crest, respectively. The sensory ganglia of the more caudal branchiomeric nerves —the facial, glossopharyngeal, and vagal nerves —are formed by a medial component that differentiates from the dorsomedial surface of migrating bands of neural crest associated with each of the developing branchial arches and with one or more lateral components that arise from epibranchial placodes located immediately dorsal and caudal to each pharyngeal pouch. Neuroblasts destined to form these sensory ganglia begin to differentiate from the epibranchial placodes as early as stage 26, whereas neural crest‐derived neuroblasts can be recognized by stage 30. Centrally directed neurites of both groups of neuroblasts enter the medulla by stage 34, and their peripherally directed neurites form recognizable rami by stage 35. Five cranial lateral line nerves, in addition to the octaval nerve, can be recognized in axolotls. Each of these nerves arises from a separate dorsolateral placode that initially gives rise to the neuroblasts of a sensory ganglion whose peripheral neurites innervate sensory receptors subsequently formed from each placode. The time course of the differentiation of these nerves and receptors is comparable to that of the branchiomeric nerves. The possible roles of rhombomeres and their associated regulatory genes and pharyngeal pouches in the induction and specification of neural crest and ectodermal placodes are explored.
Glial cell line‐derived neurotrophic factor supports survival of injured midbrain dopaminergic neurons
Authors: Bowenkamp Kathryn E. , Hoffman Alexander F. , Gerhardt Greg A. , Henry Michael A. , Biddle Paul T. , Hoffer Barry J. , Granholm Ann‐Charlotte E.
Published: January 2005

Glial cell‐lined derived neurotrophic factor (GDNF) has been shown to promote survival of developing mesencephalic dopaminergic neurons in vitro. In order to determine if there is a positive effect of GDNF on injured adult midbrain dopaminergic neurons in situ, we have carried out experiments in which a single dose of GDNF was injected into the substantia nigra following a unilateral lesion of the nigrostriatal system. Rats were unilaterally lesioned by a single stereotaxic injection of 6‐hydroxydopamine (6‐OHDA; 9 μg/4 μl normal saline with 0.02% ascorbate) into the medial forebrain bundle and tested weekly for apomorphine‐induced (0.05 mg/kg s. c. ) contralateral rotation behavior, Rats that manifested >300 turns/hour received a nigral injection of 100 μg GDNF, or cytochrome C as a control, 4 weeks following the 6‐OHDA lesion, Rotation behavior was quantified weekly for 5 weeks after GDNF. Rats were subsequently anesthetized, transcardially perfused, and processed for tyrosine hydroxylase immunohistochemistry. It was found that 100 μg GDNF decreased apomorphine‐induced rotational behavior by more than 85%. Immunohistochemical studies revealed that tyrosine hydroxylase immunoreactivity was equally reduced in the striatum ipsilateral to the lesion in both cytochrome C and GDNF‐injected animals. In contrast, large increments in tyrosine hydroxylase immunoreactivity were observed in the substantia nigra of animals treated with 100 μg of GDNF, with a significant increase in numbers of tyrosine hydroxylase‐immunoreactive cell bodies and neurites as well as a small increase in the cell body area of these neurons. The results suggest that GDNF can maintain the dopaminergic neuronal phenotype in a number of nigral neurons following a unilateral nigrostriatal lesion in the rat.
Spatial and temporal pattern of purkinje cell degeneration in shaker mutant rats with hereditary cerebellar ataxia
Authors: Tolbert D. L. , Ewald M. , Gutting J. , La Regina M. C.
Published: January 2005

Temporal‐spatial patterns of surviving Purkinje cells were studied quantitatively in a rat mutant (shaker) with differential hereditary cerebellar ataxia and Purkinje cell degeneration. Shaker rat mutants are characterized behaviorally as mild if they are ataxic or as strong if they have ataxia and tremor. Purkinje cells degenerate in both mild and strong shaker mutants, but the temporal and spatial patterns of cell death are strikingly different. In mild shaker mutants, Purkinje cell death is temporally restricted, with 31‐46% of the Purkinje cells in lobules I‐IX dying by 3 months of age. Very few Purkinje cells degenerate after this age. Purkinje cell death is spatially random. In lobules I‐IX, every second, third, or fourth Purkinje cell degenerates. Purkinje cells in lobule X do not degenerate. In strong shaker mutants, Purkinje cell degeneration is temporally protracted and spatially restricted. By 3 months of age, most Purkinje cells in lobules I‐VIa, ‐b, and ‐d, and ‐d have degenerated. Numerous Purkinje cells in the paravermis of lobules VIIb‐VIII have also degenerated. Surviving Purkinje cells in the vermis and lateral hemisphere of lobules VIIb‐VIII are aligned in parasagittally oriented stripes or transversely oriented bands. Purkinje cells continue to degenerate in localized areas of the posterior lobe such that, by 18 months of age, surviving Purkinje cells are limited primarily to lobules VIc, VIIa, IXd, and X. Quantitative analysis indicates that none of the Purkinje cells in these lobules degenerate.
Ipsilateral intracortical connections of physiologically defined cutaneous representations in areas 3b and 1 of macaque monkeys: Projections in the vicinity of the central sulcus
Authors: Burton Harold , Fabri Mara
Published: January 2005

This study examined cortical connections of areas 3b and 1 in 17 macaque monkeys in reference to regional somatotopography. The fluorescent retrograde tracers Fast Blue and Diamidino Yellow and the anterograde tracer Rhodamine Dextran were injected into closely related cutaneously responsive sites in primary somatosensory cortex, e. g., adjacent digits.

Supra‐ and infragranular layers in nearly all studied areas contained labeled pyramidal cells. Labeled infragranular cells predominated at the fringes of a distribution where cells labeled from different tracer injections in the same brain intermixed more.

All topographical regions across area 1 have reciprocal connections with areas 4, 3a, 3b, 1, 2, and 5. Intrinsic connections within area 1 and between it and area 2 are greatest; those with area 3b are less. Intrinsic connections within area 3b exceed all other nearby projections from this area which reciprocally connects with areas 3a, 1 and 2. Connections appear topographically organized, including those with poorly mapped regions, like area 5. These connections link representations of neighboring skin and skip map regions that include disjoint dermatomal areas. Connections from adjacent digit representations overlap; however, double‐labeled cells were not found. Distal and proximal digit zones mostly interconnect within an area. Intrinsic connections spread further in area 1 than in area 3b, thereby joining more disparate topographical zones than interareal connections, which project more homotopically. The domain over which the map in somatosensory cortical area I (SI) dynamically changes following in tracortical microstimulation (Recanzone, Merzenich and Dinse, Cerebral Cortex 2:181‐196, 1992) may depend on the range of intrinsic connections observed in this study. The extent of connections between cortical areas was less than expected and this challenges the hypothesis that these connections directly create receptive field enlargements.