bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential expression of GABAA/benzodiazepine receptor β1, β2, and β3 subunit mRNAs in the developing mouse cerebellum
Authors: Zdilar Darko , Luntz‐Leybman Vera , Frostholm Adrienne , Rotter Andrej
Published: January 2005

Gamma aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian cerebellum. Cerebellar granule, Purkinje, and deep nuclear neurons are known to receive GABAergic afferents. Since GABA exerts its inhibitory effects via GABA receptors, it is of interest to determine the temporal relationship between the formation of GABAergic synapses and the expression of genes coding for the GABA receptor. In a previous study, we have examined the developmental expression of binding sites for [3H] muscimol, which binds with high affinity to the β subunits of the GABAA/benzodiazepine (GABAA/BZ) receptor. In the present study, [35S]cRNA probes were used to examine the appearance and distribution of GABAA/BZ β1, β2, and β3 subunit mRNAs in the developing C57BL/6 mouse cerebellum by in situ hybridization. In the adult cerebellum, the distribution of the three subunit mRNAs was clearly different, despite considerable overlap, and their temporal expression differed throughout postnatal development. The β1 hybridization signal appeared within the cerebellar cortex during the second postnatal week as a discrete band at the interface of the molecular and granule cell layers. Grains were distributed diffusely over small densely staining cells surrounding the Purkinje cells; relatively few grains were visible over Purkinje cell bodies themselves. This distribution may reflect an association with Bergmann glia or basket cells. The β2 and β3 hybridization signals were present considerably earlier than that of the β1 mRNA. The β2 signal was present at birth in the molecular/Purkinje cell layer; as development progressed, the signal became increasingly intense over both granule and Purkinje cells. At birth, the β3 subunit mRNA was present in the external germinal and molecular layers, later becoming largely localized within the granule cell layer. Dense β2 and β3 cRNA probe labeling was present over the adult granule cell layer. Moderate levels of β2 signal were seen over Purkinje cell bodies; considerably less labeling was observed with the β3 probe. The adult distribution of β2 and β3 cRNA probes showed good spatial correspondence with the known GABAA receptor β subunit markers, [3H]‐muscimol and the mAb 62‐3G1 antibody, each being present within the granule cell layer.

Our results indicate that the temporal expression of GABAA/BZ receptor β subunit messages within a given cell type may be independently regulated, and that acquisition of the β2 and β3 mRNAs occurs before these cells become integrated into mature synaptic circuits. © 1992 Wiley‐Liss, Inc.
Two distinct phases characterize maturation of neurons in the nucleus of the tractus solitarius during early development: Morphological and electrophysiological evidence
Authors: Kalia M. , Schweitzer P. , Champagnat J. , Denavit‐Saubie M.
Published: January 2005

We have used electrophysiology and light microscopy of intracellularly labeled neurons in the nucleus of the tractus solitarius (nTS) in brainstem slices of the newborn rat (PO to P6) to examine the functional and morphological correlation of their development. Three‐dimensional reconstruction of neurons injected intracellularly with biocytin, following electrophysiological recording, revealed a close correspondence between morphological immaturity (appearing as polarization of the dendritic tree) and the absence of a ramp‐like voltage trajectory at the offset of hyperpolarizing current injections–lA negativity (8 of the 8 cells examined showed this correlation). These morphologically polarized IA negative neurons showed preferential dendritic sprouting in two diametrically opposite poles of the perikaryon.

The orientation of the polarity differed according to the rostrocaudal location of the neuron. The appearance of a polarized dendritic tree during the first (immature) phase was transient and closely coincident with IA negativity. Following the development of adult‐like electrophysiological characteristics, i.e., IA positivity, nucleus of the tractus solitarius neurons showed remarkably different morphological features (9 of 10 cells). These included a widespread branching of the dendritic tree in all directions, giving it a bushy appearance (cell body to dendrite ratio of 1:40). Numerous dendritic spines, growth cones on both dendrites and axons, and axon collateralization were present during both phases and indicate that nTS neurons during the two phases of early development demonstrate dynamic features of growth and maturation. The development of adult‐like electrophysiological characteristics, i.e., IA positivity, progressively increased in the postnatal period. During the later part of the first postnatal week, twice as many neurons showed IA positivity in days P3 to P6 as compared with days PO to P2. These results reveal the dynamic nature of neurons in the nTS during early development and illustrate the close link between morphology and functional characteristics in this region. We suggest that the establishment of adult‐like morphology can be modified by appropriate environmental clues provided to nTS neurons during the initial (immature) phase of early postnatal development. © 1993 Wiley‐Liss, inc.
Estrogen receptors in the avian brain: Survey reveals general distribution and forebrain areas unique to songbirds
Authors: Gahr Manfred , Güttinger Hans‐Rudolf , Kroodsma Donald E.
Published: January 2005

Estrogens play an important role in the control and differentiation of species‐typical behavior and in endocrine homeostasis of birds, but the distribution and evolution of cells that contain estrogen receptors in the avian brain are poorly understood. This study therefore surveys 26 species in the avian orders Anseriformes (1 species), Galliformes (2), Columbiformes (3), Psittaciformes (1), Apodiformes (2), and Passeriformes (3 suboscines, 14 oscines). Indirect immunocytochemistry with the estrogen receptor (ER) antibody H222Spy revealed a general pattern of ER‐antibody‐immunoreactive cells (ER‐IRC) in all 26 species, with ER‐IRC in consistent, well‐defined locations in the limbic forebrain, the midbrain striatum, the hippocampus, the hindbrain, and especially in the preoptic area and the tuberal hypothalamus. For some species, the microdistribution of ER‐IRC in some of these general areas differed, such as in the hippocampus and the anterior hypothalamus of suboscine species and in the preoptic area of the Japanese quail. Brains of oscine songbirds of both sexes, unlike brains of nonsongbirds, had ER‐IRC in three specific structures of the nonlimbic forebrain: in the area surrounding the nucleus robustus archistriatalis; in the rostral forebrain; and, for all individuals, in the caudale neostriatum, including the nucleus hyperstriatalis ventrale, pars caudale (HVc). Among songbird families or subfamilies, adult males of the Estrildinae had much lower numbers of ER‐IRC in HVc than did adult males of the Fringillidae, Paridae, Sturnidae, and Ploceinae. Differences occurred, too, among closely related species: the songbird canary (Serinus canaria) had an ER‐IRC area in the rostral forebrain that was lacking in all other songbird species, including other cardueline finches. The cells with ER that are found only in the songbird forebrain but not in reptiles, nonpasserine birds, and nonoscine passerine birds very likely coevolved with steroid‐dependent differentiation of vocal control areas. The songbird‐specific expression of ER in the forebrain could be an example in which taxon‐specific behavior is due to taxon specific neurochemical properties of the brain. © 1993 Wiley‐Liss, Inc.
Characterization of microglial reaction after middle cerebral artery occlusion in rat brain
Authors: Morioka Takato , Kalehua Audrey N. , Streit Wolfgang J.
Published: January 2005

We have studied the microglial reaction that accompanies cortical infarction induced by middle cerebral artery occlusion (MCAO). Lectin histochemistry with the B4‐isolectin from Griffonia simplicifoliaas well as immunocytochemistry with a panel of monoclonal antibodies directed against major histocompatibility complex (MHC) and lymphocytic antigens were performed. Principal attention was focused on neocortical and thalamic regions, representative of primary and secondary ischemic damage, respectively. With the lectin procedure, activated microglial cells were abundant in the neocortex 24 hours after MCAO. In contrast, microglial activation in the thalamus was not apparent until day 2 after MCAO. On day 5, MHC class II antigen was expressed by reactive microglia in fiber tracts traversing the striatum, but was absent from activated microglia in the primary cortical infarction area. MHC class I and lymphocytic antigens were expressed differentially on microglia with class I antigens appearing early and lymphocytic antigens appearing late in the time course after focal ischemia. The findings are compatible with previous studies during global ischemia and confirm the early activation and the progressive nature of immunomolecule expression on activated microglia after an ischemic insult. In addition to neocortical and thalamic sites, our results showed an early microglial activation to be present also in forebrain regions outside of the middle cerebral artery (MCA) territory, such as the contralateral cortex and hippocampus. A unilateral microglial reaction was also detectable after long‐term survival (≥4 weeks) in the pyramidal tracts, as well as in the corticospinal tracts at cervical but not lumbar spinal cord levels. Ischemia‐induced neuronal damage, as evaluated by Nissl staining, was found only in cortical and thalamic regions. We conclude that the demonstration of reactive microglia indicates not only imminent ischemic neuronal damage within MCA territory but can also delineate extra‐focal disturbances, possibly reflecting subtle and transitory changes in neuronal activity. © 1993 Wiley‐Liss, Inc.
Organization of visual corticostriatal projections in the cat, with observations on visual projections to claustrum and amygdala
Authors: Updyke B. V.
Published: January 2005

Electrophysiological mapping criteria were employed to identify visual areas 20a, 20b, 21a, 21b, PMLS, AMLS, ALLS, PLLS, DLS, VLS, and PS in the cat, and to guide placement of tracer deposits. Anterograde tracer methods were used to study the corticostriatal projections of these extrastriate visual areas. The experiments demonstrate that all 11 extrastriate areas send projections to two distinct regions within the striatum, an extensive longitudinal zone within the caudate nucleus, and a more compact region within the posterolateral putamen. Cortical visual projections to the putamen terminate in relatively compact sheets or slabs, and appear to overlap extensively, while those to the caudate nucleus are irregularly patchy and more widely dispersed. Retrograde tracer deposits into the visual recipient zone of the caudate nucleus reveal substantial convergence of other cortical inputs to this same domain. Aspects of visuotopic organization are preserved in the visual projections to both the putamen and the caudate nucleus, but unequivocal retinotopic organization could not be inferred from the available material.

Ten of the eleven extrastriate visual area also project topographically onto the visual zone of the claustrum. Area PS does not appear to contribute to the corticoclaustral projections. Five of the extrastriate visual areas (ALLS, PLLS, DLS, VLS, PS) also send sparse projections to the amygdaloid complex. c 1993 Wiley‐Liss, Inc.
Anatomical and physiological study of brainstem nuclei relaying dorsal column inputs in lampreys
Authors: Dubuc Réjean , Bongianni Fulvia , Ohta Yoshihiro , Grillner Sten
Published: January 2005

The course and sites of termination of dorsal column fibres in the lamprey brainstem are described along with their brainstem relays projecting to reticulospinal neurons. Dorsal column fibres ascend to the brainstem level where they intermingle with cells located in the alar plate close to the obex, a location that is analogous to that of the dorsal column nucleus in other vertebrates. Some dorsal column fibres continue further rostrally where they reach the octavolateralis and octavomotorii nuclei. Finally, a small contingent of fibres reach the cerebellum. Injections of cobalt‐lysine into the posterior rhombencephalic reticular nucleus retrogradely label neurons within the dorsal column nucleus and within the octavolateralis and octavomotorii nuclei. Microstimulation of the dorsal column nucleus on either side elicits monosynaptic inhibitory responses in reticulospinal neurons while stimulation of octavolateralis and octavomotorius nuclei elicits excitation. By using intracellular recordings, it was shown that neurons within these alar plate nuclei receive monosynaptic inputs from the dorsal columns. It is thus proposed that disynaptic inputs from dorsal columns to reticulospinal neurons are relayed by these alar plate neurons: inhibition is relayed mainly by neurons in dorsal column nuclei and excitation by neurons in the octavolateralis and octavomotorii nuclei. © 1993 Wiley‐Liss, Inc.
Barrelettes—architectonic vibrissal representations in the brainstem trigeminal complex of the mouse. II. Normal post‐natal development
Authors: Ma Pokay M.
Published: January 2005

Vibrissal representations in the brainstem trigeminal complex (BTC) of rodents are manifested as architectural sub‐units called barrelettes. The development of barrelettes was studied by using Nissl staining, cytochrome oxidase histochemistry, and Golgi‐impregnation methods. On the day of birth (PND‐1), barrelettes are manifested as longitudinal, histochemical cylinders in sub‐nuclei principalis, interpolaris and caudalis of the BTC. One day later (PND‐2), fully formed histochemical barrelette formations are seen in the three sub‐nuclei. The development of cytoarchitectural barrelettes lags behind histochemical barrelettes by about two days. Between PND‐2 and PND‐3, longitudinal cytoarchitectonic cylinders begin to appear. By PND‐3, BTC neurons segregate into five rows of barrelettes in the coronal plane. Segmentation of rows into individual barrelettes begins on PND‐4, and complete cytoarchitectonic barrelette formations are seen by PND‐5. Golgi‐impregnation shows that on the day of birth, primary afferent terminals and dendritic arbors of second‐order trigeminal neurons within the BTC are short and poorly ramified. Over the next five post‐natal days, lengthening of these processes as well as elaboration into secondary and tertiary branches take place. Growth of these processes continues for two additional weeks, contributing to the increase in barrelette neuropils (hollows). As the neuropils expand, neuronal somata are pushed toward barrelette sides. Morphometric measurements show that there is a relatively constant rate of growth of barrelettes over the first three post‐natal weeks. The growth rate of the barrelette formations is identical to that of BTC as a whole. Thus, at the time of birth, the volume of neural tissue in the brainstem allotted to vibrissae is fixed relative to that allotted to other sensory receptors.

Several features of the early development of barrelettes are identified: (1) Chemoarchitectural barrelettes appear before cytoarchitectural barrelettes, suggesting that terminal arbors of primary trigeminal afferents are organized before their target neurons form barrelettes. (2) Early cytoarchitecture is manifested in the form of unsegmented rows, suggesting that rough, row‐based topological maps are first formed, which are then fine‐tuned into individual sub‐units. Recent evidence shows that other vibrissal representations—thalamic barreloids and cortical barrels—also follow these “afferent‐before‐target” and “row‐before‐individual units” sequences of development. This gradual, afferent‐dependent fine‐tuning of topological organization is analogous to similar events during the early development of the visual system, and may be a general feature of developing sensory systems. In the visual system, sensory input plays an important role in fine‐tuning centers in the brain; the mechanisms by which barrelettes are organized and fine‐tuned are still unknown. 1993 Wiley‐Liss, Inc.
Distribution, parabrachial region projection, and coexistence of neuropeptide and catecholamine cells of the nucleus of the solitary tract in the pigeon
Authors: Berk Mitchell L. , Smith Stacy E. , Mullins Lee A.
Published: January 2005

The chemical nature of the cells of the nucleus of the solitary tract (NTS) that project to the parabrachial nucleus (PB) was investigated in the pigeon by the use of fluorescent bead retrograde tracer and immunofluorescence for the detection of substance P (SP), leucineenkephalin (LENK), cholecystokinin (CCK), neurotensin (NT), somatostatin (SS), and tyrosine hydroxylase (TH). Cells immunoreactive for CCK were located in subnuclei lateralis dorsalis pars anterior (LDa) and medialis superficialis pars posterior, and caudal NTS (cNTS); 22–26.5% of these cells were double‐labeled bilaterally. Immunoreactive SP cells were found in ventral NTS subnuclei; 24–25% of these cells were double‐labeled bilaterally. Cells immunoreactive for LENK and NT were concentrated in the anterior NTS; 5.5–7.5% of the LENK cells were double‐labeled bilaterally, while 11% (ipsilateral) and 21% (contralateral) of the NT immunoreactive cells were double‐labeled. Many SS immunoreactive cells were found in peripherally located subnuclei; 5.5–6.5% of these cells were double‐labeled bilaterally. Catecholamine cells were distributed in LDa, peripheral subnuclei, and cNTS; 23% of these cells were double‐labeled ipsilaterally and 8.5% contralaterally. A two‐color double‐labeling immunofluorescence technique revealed many cells immunoreactive for both NT and LENK, only a rare cell immunoreactive for both SS and SP, and no cells immunoreactive for both TH and SP.

Cells immunoreactive for SP, CCK, NT, and TH are major contributors to NTS projections to PB. The confinement of these substances to specific NTS subnuclei, which receive visceral sensory information from specific organs, may contribute to the chemical encoding of ascending visceral information. 1993 Wiley‐Liss, Inc.
Connections of somatosensory cortex in megachiropteran bats: The evolution of cortical fields in mammals
Authors: Krubitzer Leah A. , Calford Mike B. , Schmid Leisa M.
Published: January 2005

The cortical connections of the primary somatosensory area (SI or 3b), a caudal somatosensory field (area 1/2), the second somatosensory area (SII), the parietal ventral area (PV), the ventral somatosensory area (VS), and the lateral parietal area (LP) were investigated in grey headed flying foxes by injecting anatomical tracers into electrophysiologically identified locations in these fields. The receptive fields for clusters of neurons were mapped with sufficient density for injection sites to be related to the boundaries of fields, and to representations of specific body parts within the fields. In all cases, cortex was flattened and sectioned parallel to the cortical surface. Sections were stained for myelin and architectonic features of cortex were related to physiological mapping and connection patterns. We found patterns of topographic and montopographic connections between 3b and adjacent anterior parietal fields 3a and 1/2, and fields caudolateral to 3b (SII and PV). Area 1/2 had both topographic and nontopographic connections with 3b, PP, and SII. Connections of SII and PV with areas 3b, 3a, and 1/2 were roughly topographic, although there was clear evidence for nontopographic connections between these fields. SII was most densely connected with area 1/2, while PV was most densely connected with 3b. SII had additional connections with fields in lateral parietal cortex and with subdivisions of motor cortex. Other connections of PV were with subdivisions of motor cortex and pyriform cortex. Laminar differences in connection patterns of SII and PV with surrounding cortex were also observed. Injections in the ventral somatosensory area revealed connections with SII, PV, area 1/2, auditory cortex, entorhinal cortex, and pyriform cortex. Finally, the lateral parietal field had very dense connections with posterior parietal cortex, caudal temporal cortex, and with subdivisions of motor cortex. Our results indicate that the 3b region is not homogeneous, but is composed of myelin dense and light regions, associated with 3b proper and invaginations of area 1/2, respectively. Connections of myelin dense 3b were different from invaginating portions of myelin light area 1/2. Our findings that 3b is densely interconnected with PV and moderately to lightly interconnected with SII supports the notion that SII and PV have been confused across mammals and across studies. Our connectional evidence provides further support for our hypothesis that area 1/2 is partially incorporated in 3b and has led to theories of the evolution of cortical fields in mammals. © 1993 Wiley‐Liss, Inc.
Functional organization of the ventral lateral geniculate complex of the tree shrew (Tupaia belangeri): II. Connections with the cortex, thalamus, and brainstem
Authors: Conley Michael , Friederich‐Ecsy Beate
Published: January 2005

Connections of the ventral lateral geniculate complex (GLv) in the tree shrew were traced by anterograde and retrograde transport of WGA‐HRP. The results buttress earlier findings that GLv in this species is composed of two main divisions, lateral and medial, each of which differs in its connections with the brainstem and cerebral cortex. The connections of the lateral division (GLv) suggest that it participates in visuosensory functions: it receives input from the retina, striate cortex, pretectum, and retino‐recipient layers of the superior colliculus. These connections help clarify the identification of the internal and external subdivisions of GLv inasmuch as projections from both the superior colliculus and pretectum terminate in the external subdivision and each, in turn, receives a projection from the internal subdivision.

Connections of the medial division suggest that this part of the nucleus is involved with visuomotor functions. Thus, the medio‐caudal subdivision projects to the pontine nuclei, the prerubral field and the central lateral nucleus. The medio‐caudal subdivision also receives projections from the lateral cerebellar nucleus, so that the GLv‐ponto‐cerebello‐GLv loop involves mainly one subdivision of GLv. The medio‐rostral subdivision receives projections from the pretectum and parietal cortex. Its output is directed primarily at the intermediate and deep layers of the superior colliculus. All of these targets of GLv, the pons, prerubral field, and deep layers of the superior colliculus, are known to play a role in the coordination of head and eye movements.

Additional connections of GLv with the vestibular nuclei, intralaminar nuclei, hypothalamus, and facial motor nucleus are also described. © 1993 Wiley‐Liss, Inc.
Regenerative outgrowth and distribution of the electroreceptive nerve fibers in the catfish Kryptopterus
Authors: Roth Anton
Published: January 2005

The ampullary electroreceptors on the trunk of Kryptopterus bicirrhis are induced and continuously maintained by a trophic substance released by their afferent nerve fibers. When the fibers are transected and the proximal stumps deflected to a new place, the regenerating fibers grow along new routes to the old electroreceptor sites and again induce organs there. The new routes consist of two sections. The first goes from the deflected stump end to other nearby running intact or degenerated nerves and fibers. In the second section, the regenerating fibers grow along these nerves and fibers to their distal ends, i.e., to the old electroreceptor sites. If the path‐guiding nerves and fibers are experimentally removed, the displaced fibers grow to the normal receptor areas directly. Growing out from the displaced stump, they spread out over the trunk in a pattern similar to the pattern displayed formerly by the original nerve fibers at this place. It is concluded that the outgrowing fibers do not possess a specificity for a certain receptor site or skin area, but spread out according to epigenetic factors in the periphery. © 1993 Wiley‐Liss, Inc.
Intrinsic connections of layer III of striate cortex in squirrel monkey and bush baby: Correlations with patterns of cytochrome oxidase
Authors: Lachica E. A. , Beck P. D. , Casagrande V. A.
Published: January 2005

This study used biocytin and horseradish peroxidase (HRP) to examine the intrinsic connections of the cytochrome oxidase (CO) rich blob and CO poor nonblob zones within layer III of striate cortex in two primate species, nocturnal prosimian bush babies (Galago crassicaudatus) and diurnal simian squirrel monkeys (Saimiri sciureus). Our main objective was to determine whether separate classes of lateral geniculate nucleus (LGN) cells projected to separate superficial layer zones or layers in either species. There were three significant findings. First, we confirm that layer III consists of three sublayers, IIIA, IIIB, and IIIC in both species. Layer IIIA receives input from layers IIIB, IIIC, and V, with little or no input from LGN recipient layers IV and VI. Layer IIIB receives its input from nearly every cortical layer. Layer IIIC, receives input principally from layers IVα [which receives its input from magnocellular (M) LGN cells] and from layers V and VI. Taken together with other findings on the extrinsic connections of these layers, our data suggest that IIIA and IIIC provide output to separate hierarchies of visual areas and IIIB acts as a set of interneurons. Second, we find that, as in macaque monkeys, cells in both IVβ and IVα of bush babies and squirrel monkeys projct to layer IIIB, converging within the blobs. These results suggest that information from all LGN cell classes [parvocellular (P), M, and the Koniocellular (K) or their equivalents] may be integrated within the blobs. Thus, blobs in all of these primates may perform a function that transcends visual niche differences. Third, our data show a species specific difference in the connections of the IIIB nonblobs; nonblobs receive indirect input via IVα from the LGN M pathway in bush babies but receive indirect input via IVβ from the LGN parvocellular (P) pathway in squirrel monkeys. These findings indicate that the role of nonblob zones within striate cortex differs from that of blob zones and takes into account visual niche differences. © 1993 Wiley‐Liss, Inc.
Localization of tyrosine hydroxylase in neuronal targets and efferents of the area postrema in the nucleus tractus solitarii of the rat
Authors: Kachidian Philippe , Pickel Virginia M.
Published: January 2005

Catecholamines in the nucleus tractus solitarii (NTS) have been implicated in autonomic responses to circulating hormones that act on neurons in the area postrema, the most caudal circumventricular organ in brain. We combined immunoperoxidase labeling of the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHAL) with immunogold‐siver labeling of tyrosine hydroxylase to determine whether this enzymatic marker for catecholamines was present in efferents from the area postrema or their targets in the rat NTS. At survival periods of 10–12 days after PHAL injections into the area postrema, light microscopy revealed numerous varicose processes containing peroxidase reaction product for PHAL in the dorsomedial, medial, and commissural NTS. Some of these labeled processes were located near neuronal perikarya and processes containing immunogold‐silver intensified reaction product for tyrosine hydroxylase. Electron microscopy of the commissural and dorsomedial NTS established that the majority of the labeling for PHAL was in axon terminals, whereas immunogold labeling for tyrosine hydroxylase was mainly in soma and dendrites. Only 3 out of 579 PHAL‐labeled terminals also contained detectable tyrosine hydroxylase immunoreactivity. Fifty‐eight percent (335/579) of the PHAL‐labeled terminals formed synapses with recognized symmetric junctions, whereas the remainder lacked synaptic specializations within the examined series of serial sections. Of those PHAL terminals forming recognized symmetric junctions, 22% were on tyrosine hydroxylase‐immunoreactive dendrites, 74% on unlabeled dendrites and 4% on unlabeled axon terminals. From a total of 1,250 observed contacts on tyrosine hydroxylase labeled dendrites, 88 (7%) contained PHAL, 9 (<1%) contained TH, and 1,180 (93%) lacked detectable immunoreactivity and formed primarily symmetric synapses. We conclude that a few catecholamine, but mainly noncatecholamine efferents from the area postrema provide a monosynaptic, and most likely inhibitory input to target neurons both with and without tyrosine hydroxylase immunoreactivity in the dorsomedial and commissural NTS. Synapses between the efferent terminals from the area postrema and tyrosine hydroxylase labeled and unlabeled dendrites as well as unlabeled axons in these specific subnuclei of the NTS suggest multiple sites for modulation of gastric and cardiovascular reflexes in response to circulating peptdies. © 1993 Wiley‐Liss, Inc.
Substance P‐like and serotonin‐like immunoreactivity in the lateral cervical nucleus of the raccoon
Authors: Broman Jonas , Pubols Benjamin H.
Published: January 2005

The distribution of substance P and serotonin in the lateral cervical nucleus (LCN) of the raccoon was examined by light microscopic immunohistochemistry.

Substance P‐immunoreactive fibers were found to be clustered in the ventromedial part of the LCN, whereas only few such fibers appeared in the dorsolateral part of the nucleus. This organization is closely similar to that previously observed in the cat, and provides further evidence for an anatomic and functional segregation along the transverse axis of the LCN in carnivores. In some sections, substance P‐positive fibers were found primarily in areas of the ventromedial LCN containing small neurons, indicating that such fibers may be involved in functions of the LCN associated with nociceptive projection neurons and/or local circuit neurons.

The raccoon LCN also received a relatively sparse innervation of serotonin‐positive fibers that were distributed throughout the nucleus, an organization similar to that previously observed in the cat. The functional role of the serotonergic fibers is unclear. However, their presence suggests that descending influences on transmission in the spinocervicothalamic pathway, in addition to the well‐documented descending control of spinocervical tract neurons, may be present also at the level of the LCN. © 1993 Wiley‐Liss, Inc.
Extra‐hypothalamic vasopressin neurons coexpress galanin messenger RNA as shown by double in situ hybridization histochemistry
Authors: Miller Margaret A. , Kolb Pamella E. , Raskind Murray A.
Published: January 2005

Vasopressin (VP) neurons in the bed nucleus of the stria terminalis (BNST) and medial amygdala (AMe) exhibit sexual dimorphism and steroid dependency. VP neurons in the supraoptic nucleus and paraventricular nucleus have been shown to coexpress other transmitters including galanin (GAL). However, little is known about what other neurotransmitters may be colocalized with VP in the BNST and AMe. Here, we have used radio‐labeled and digoxigenin‐labeled cRNA probes to perform double in situ hybridization histochemistry for VP and GAL in the BNST and AMe of intact, adult male rats. We provide evidence that in the basal state, the majority of VP‐synthesizing cells in the BNST and AMe of the adult male rat also express galanin mRNA. Likewise, the majority of GAL‐expressing neurons in these regions also contain VP mRNA. These findings give further evidence for the similarity of the BNST and AMe and provide a rationale for studies investigating the role of GAL in functions involving extrahypothalamic VP pathways. © 1993 Wiley‐Liss, Inc.
Distribution of [3H]QNB and [125I]α‐bungarotoxin binding and acetylcholinesterase activity in visual system and hippocampal structures of eleven mammalian species
Authors: Fuchs Jannon L. , Schwark Harris D.
Published: January 2005

This study assessed interspecies differences in regional brain distribution of [3H]QNB binding, [125I]α‐bungarotoxin binding and acetylcholinesterase activity, by autoradiographic and histochemical methods. Eleven mammalian species were examined, including carnivores (cat, dog), a lagomorph (rabbit), and rodents (squirrel, guinea pig, gerbil, hamster, vole, lemming, rat, mouse). Comparisons were based on primary visual system structures (superior colliculus, lateral geniculate nucleus, primary visual cortex) and the hippocampal formation. The two radioligands differed greatly in the degree of interspecies variation: while the pattern of [3H]QNB binding was quite similar across species, [125I] α‐bungarotoxin showed striking interspecies diversity. This contrast was most obvious in laminar patterns of the visual cortex and hippocampal formation. Regional distributions of acetylcholinesterase staining were fairly diverse, and were unlike the patterns of either [3H]QNB or [125I]α‐bungarotoxin. The two ligands showed more consistency in overall levels across species than did acetylcholinesterase. Possible correlates of the differences in interspecies diversity are discussed. © 1993 Wiley‐Liss, Inc.
Synaptophysin immunohistochemistry reveals inside‐out pattern of early synaptogenesis in ferret cerebral cortex
Authors: Voigt Thomas , De Lima Ana D. , Beckmann Matthias
Published: January 2005

Synaptogenesis in the ferret cerebral cortex was examined from the day of birth to adulthood with an antibody against synaptophysin at the light and electron microscopic levels. Due to the premature birth of ferrets, the generation of cells destined to the upper cortical layers and their subsequent migration to their final positions in the cortical plate are largely postnatal events.

Throughout the newborn ferret cerebral cortex, a high amount of synaptophysin immunoreactivity was present within the marginal zone and subplate region. Staining was also conspicuous within the forming cortical plate. The typical layering pattern of synaptophysin immunoreactivity in the developing cortical plate correlated with the migration pattern of cortical neurons. The synaptic density was lowest directly below the marginal zone, where the youngest neurons just stopped their migration. Below this zone, the density of the synaptic staining increased gradually toward lower (and older) cortical plate layers. As the cortex expanded, the synaptophysin immunoreactivity pattern closely followed the expansion, suggesting that synapses were formed in a given layer shortly after the cells migrating to this layer reached their final position. As soon as cell migration had finished, the entire cortical plate contained dense synaptophysin immunoreactivity, in a pattern similar to that observed in the adult animal. During cortical development, a rostrocaudal and a laterodorsal gradient of synaptogenesis was observed. At any given time, rostral and lateral regions of the cerebral cortex were more advanced in their development than caudal and dorsal regions.

Electron microscopic examination of synaptophysin immunoreactivity in the developing cerebral cortex of ferrets confirmed that labeling was solely associated with synaptic vesicles. These vesicles were typically, but not exclusively, confined to synaptic boutons. Especially around the end of the first postnatal week, long fiber profiles loaded with synaptic vesicles were occasionally detected. As some of these fibers also showed en passant synapses along their course, we concluded that synaptic vesticle labeling may be reliably used to study synaptogenesis at the light microscopic level. A systematic analysis of samples from postnatal days 0 and 7 corroborated this conclusion, showing that synaptic profile distribution completely matched the distribution of synaptophysin immunoreactivity seen in the light microscope.

In conclusion, synaptogenesis begins as soon as migratory cells reach their final position in the cortical plate. As long as cell migration continues, synaptogenesis is under the constraints of neurogenesis, following its gradients.
Histaminergic system in the cat hypothalamus with reference to type B monoamine oxidase
Authors: Lin J. S. , Kitahama K. , Fort P. , Panula P. , Denney R. M. , Jouvet M.
Published: January 2005

It is known that histamine (HA) and type B monoamine oxidase (MAO‐B), an enzyme involved in its metabolism, are present in the posterior hypothalamus, but the sites where MAO‐B intervenes in HA metabolism remain uncertain. The present study examined and compared the detailed distribution and morphology of neurons immunoreactive to HA (HA‐ir) and MAO‐B (MAO‐B‐ir) in the cat hypothalamus. HA‐ir neurons were localized almost exclusively in the posterior hypothalamus with the largest group in the tuberomammillary nucleus and adjacent areas. MAO‐B‐ir staining was detected in the vast majority of HA‐ir neurons, suggesting that the degradation of tele‐methylhistamine (t‐MHA), the direct metabolite of HA, may occur within these cells. Nevertheless, a few HA‐ir cells showed no detectable or very weak MAO‐B‐ir labeling; a small group of neurons containing MAO‐B alone was detected in the area dorsolateral to the caudal part of the arcuate nucleus. Numerous HA‐ir axons and terminal‐like structures were distributed unevenly in virtually all hypothalamic regions. One of their principal trajectories ascended through the ventrolateral part of the hypothalamus and rostrally formed an axon column, which ascended into the preoptic area and contributed fibers to the diagonal band of Broca and bed nucleus of the stria terminalis. Other HA‐ir axons passed laterally, dorsal to the zona incerta or ventrally through a narrow zone dorsal to the optic tract. Numerous long HA‐ir axons coursed dorsomedially from the ventrolateral posterior hypothalamus to the dorsal hypothalamic area. Many are oriented vertically to the thalamus in the midline. MAO‐B‐ir axons and fibers were detectable throughout the hypothalamus and overlapped the areas distributing HA‐ir fibers. They were, however, weaker in staining intensity and apparently fewer than the HA‐ir fibers. MAO‐B‐ir glial cells were numerous in all hypothalamic structures rich in HA‐ir fibers. These results suggest that the metabolism of t‐MHA may also occur within HA terminals and glial cells.
Synapses of extrinsic and intrinsic origin made by callosal projection neurons in mouse visual cortex
Authors: Czeiger David , White Edward L.
Published: January 2005

Neurons in areas 17/18a and 17/18b of mouse cerebral cortex were labeled by the retrograde transport of horseradish peroxidase (HRP) transported from severed callosal axons in the contralateral hemisphere. Terminals of the local axon collaterals of labeled neurons (intrinsic terminals) were identified in the border regions of area 17 with areas 18a and 18b, and their distribution and synaptic connectivity were determined. Also examined were the synaptic connections of extrinsic callosal axon terminals labeled by lesion‐induced degeneration consequent to the severing of callosal fibers. A postlesion survival time of 3 days was chosen because by this time the extrinsic terminals were all degenerating, whereas the intrinsic terminals were labeled by horseradish peroxidase.

Both intrinsic and extrinsic callosal axon terminals occurred in all layers of the cortex where, with rare exception, they formed asymmetrical synapses. Layers II and III contained the highest concentrations of intrinsic and extrinsic callosal axon terminals. Analyses of serial thin sections through layers II and III in both areas 17/18a and 17/18b yielded similar results: 97% of the intrinsic (1,412 total sample) and of the extrinsic (414 total sample) callosal axon terminals synapsed onto dendritic spines, likely those of pyramidal neurons; the remainder synapsed onto dendritic shafts of both spiny and nonspiny neurons. Thus, the synaptic output patterns of intrinsic vs. extrinsic callosal axon terminals are strikingly similar. Moreover, the high proportion of axospinous synapses formed by both types of terminal (97%) contrasts with the proportion of asymmetrical axospinous synapses that occurs in the surrounding neuropil where about 64% of the asymmetrical synapses are onto spines. This result is in accord with previous quantitative studies of the synaptic connectivities of callosal projection neurons in mouse somatosensory cortex, and lends additional weight to the hypothesis that axonal pathways are highly selective for the types of elements with which they synapse.
Aminergic and cholinergic afferents to REM sleep induction regions of the pontine reticular formation in the rat
Authors: Semba Kazue
Published: January 2005

Microinjection of cholinergic agonists in a dorsolateral part of the mesopontine tegmentum has been shown to induce a rapid eye movement (REM) sleep‐like state. Physiological evidence indicates that not only acetylcholine but also various amine transmitters, including those implicated in behavioral state regulation, affect neuronal activity in this region of the pontine reticular formation. In the present study, sources of select aminergic and cholinergic inputs to this REM sleep induction zone were identified and quantitatively analyzed by using fluorescence retrograde tracing combined with immunofluorescence in the rat.

In addition to previously demonstrated cholinergic projections from the pedunculopontine and laterodorsal tegmental nuclei, the REM sleep induction zone received various aminergic inputs that originated in widely distributed regions of the brainstem and hypothalamus. Serotoninergic afferents represented a mean of 44% of all aminergic/cholinergic source neurons projecting to the REM sleep induction zone, which was comparable to the mean percentage of 39% represented by cholinergic afferent neurons. The serotoninergic afferents originated from the raphe nuclei at all brainstem levels, with heavier projections from the pontine than from the medullary raphe nuclei. Unexpectedly, an additional major serotoninergic input was provided by serotoninergic neurons in the nucleus prosupralemniscus (B9). Noradrenergic afferent neurons represented a mean of 14% of all aminergic/cholinergic source neurons, which was only about one‐third of the mean percentage of either cholinergic or serotoninergic source neurons. These noradrenergic projection neurons were located not only in the locus ceruleus (8%) but also in the lateral tegmentum, including the A5 (4%) and A7 (2%) cell groups. Histaminergic neurons in the tuberomammillary hypothalamic nucleus represented a minor group of afferent neurons (3%), and a still smaller input came from adrenegic C1 neurons. The pattern of these transmitter‐specific afferent connections appeared to be similar regardless of the longitudinal level within the REM sleep induction zone.

The present results are consistent with previous behavioral and physiological evidence for a role of the pontine REM sleep induction zone in triggering REM sleep. The regulation of REM sleep induction would be best understood in terms of a state‐dependent interplay of cholinergic, serotoninergic, and other inputs all acting convergently upon neurons in the REM sleep‐inducing region of the pontine reticular formation.
Morphological correlates of functional recovery in the chicken inner ear after gentamycin treatment
Authors: Duckert Larry G. , Rubel Edwin W
Published: January 2005

Newly hatched chickens were allowed to survive 6, 10, 15, and 20 weeks after 10 days of gentamycin sulfate treatment. Ultrastructural studies of hair cells and nerve terminals in the auditory receptor organ, the basilar papilla, were carried out with transmission and scanning electron microscopes. Attention was paid to absolute sensory cell (hair cell) numbers, stereocilia maturity and orientation, and reinnervation within a band 100 μm wide centered 1,100 μm from the basal end of the avian cochlea.

Sensory cell numbers were equivalent to those of untreated control animals within the study area in the earliest survival group. Both immature and mature appearing hair cells were identified throughout the recovery period. However, the ratio of mature to immature hair cells gradually increased to exceed 95% at 20 weeks. Stereocilia bundle reorientation also occurred throughout the study period. Orientation was often abnormal at 6 weeks, but by 20 weeks more than 95% of the regenerated hair cells were aligned within normal limits established in the control ears. Hair cell differentiation occurring at 10–15 weeks was associated with degeneration of the afferent nerve receptor complexes commonly observed in 6 week survivors. These complexes were replaced by one or two small bouton shaped efferent terminals per cell. At 20 weeks, two or three chalice shaped vesiculated terminals were observed per cell in both the gentamycin treated and control ears.

On the basis of these observations normal physiological activity would be predicted at 20 weeks following gentamycin treatment, at which time sensory cell repopulation, maturation, reorientation, and innervation approximates the normal anatomical condition. © 1993 Wiley‐Liss, Inc.
Transcellular labeling by dil demonstrates the glossopharyngeal innervation of taste buds in the lingual epithelium of the axolotl
Authors: Nagai Takatoshi
Published: January 2005

Innervation of the axolotl lingual epithelium by the glossopharyngeal nerve was examined to reveal its sensory target cells. The carbocyanine dye diI was applied to the nerve stump in the tongue fixed with paraformaldehyde. After a diffusion period of several months, the tongues were examined with a conventional epifluorescence microscope and a confocal laser scanning microscope (LSM) in wholemounts or preparations sectioned with a vibratome. Beneath the epithelium the labeled nerve fibers spread horizontally to form a meshwork of fibers, from which fascicles of fibers extended upward perpendicularly to the epithelium to innervate taste buds. Numerous taste buds were labeled by possible transcellular diffusion of diI. At the base of the taste bud, the nerve fibers branched and formed a basal plexus of fine fibers, on which numerous varicosities were seen. One or at most several taste cells were labeled in a taste bud. In the basal part of taste buds, the cell without an apical process, the basal cell, was also labeled. In the epithelium, between the taste buds, a few solitary cells were labeled. In some cases, a single fascicle of fibers innervating these cells was clearly shown by the LSM. In addition, fine fibers apparently formed free nerve endings in the epithelial cell layer. The results showed that the IX nerve innervated not only taste cells, but also presumed mechanosensory basal cells in the taste bud and the solitary cells of unknown function in the non‐taste lingual epithelium. Afferent nerve responses to mechanical stimulation of the tongue may be explained by these non‐taste cellular elements in the epithelium. © 1993 Wiley‐Liss, Inc.