bluuebunny/crossref_metadata_2025_split huggingface dataset:
GABA: A dominant neurotransmitter in the hypothalamus
Authors: Decavel Chantal , Van Den Pol Anthony N. 
Published: January 2005

AbstractTo study the organization and distribution of the inhibitory amino acid neurotransmitter GABA in the medial hypothalamus, we used a postembedding immunocytochemical approach with colloidal gold. Quantitative analysis showed that half (49%) of all synapsing boutons studied were immunoreactive for GABA, based on immunogold staining of the suprachiasmatic, arcuate, supraoptic, and paraventricular nuclei. This was corroborated with pre‐embedding peroxidase immunostaining with antisera against glutamate decarboxylase, the GABA synthetic enzyme. These data suggest that GABA is the numerically dominant neurotransmitter in the hypothalamus, and emphasize the importance of inhibitory circuits in the hypothalamus.Serial ultrathin sections were used to reconstruct GABA immunoreactive boutons and axons in three dimensions. With this type of analysis we found less morphological heterogeneity between GABA immunoreactive boutons than with single ultrathin sections. Single sections sometimes showed boutons containing only small clear vesicles, and others with both clear vesicles and small dense core vesicles. However, with serial sections through individual boutons, dense core vesicles were consistently found at the periphery of the pre‐synaptic GABA immunoreactive boutons, suggesting probable co‐localization of GABA with unidentified peptides in most if not all boutons throughout the hypothalamus.A positive correlation was found between the density of small clear vesicles and the intensity of immunostaining with colloidal gold particles. GABA immunoreactive axons generally made symmetrical type synaptic specializations, although a small percentage made strongly asymmetrical synaptic specializations. Vesicles in GABA immunoreactive boutons were slightly smaller than those in non‐reactive boutons.Synaptic efficacy is related to the position of the synapse on the post‐synaptic neuron. While the majority of GABA immunoreactive axons made synaptic contact with dendrites, the distribution of GABA immunoreactive synapses on somata and dendrites was the same as would be expected from a random distribution of all boutons. No preferential innervation of cell bodies by GABA immunoreactive terminals was found. Serial ultrathin sections showed that a GABA immunoreactive axon would sometimes make repeated synaptic contacts with a single postsynaptic neuron, indicating a high degree of direct control by the presynaptic GABAergic cell. Other immunoreactive axons made synaptic contact with a number of adjacent dendrites and cells, suggesting a role for GABA in synchronizing the activity of hypothalamic neurons. Based on the density of immunogold particles per unit area, varying concentrations of immunoreactive GABA were found in different presynaptic boutons in the hypothalamus.
Light‐stimulated rhabdom turnover in Limulus ventral photoreceptors maintained in vitro
Authors: Herman Karen G. 
Published: January 2005

AbstractThe role of light in turnover of photosensitive membranes was studied in isolated photoreceptors maintained in vitro. Ventral photoreceptors of the horseshoe crab, Limulus polyphemus, were used since they have been the subjects of many in vitro physiological studies. This study shows that the two classes of ventral photoreceptors, the large and small photoreceptors (Herman: companion paper), differ in their morphological response to light. The rhabdom of small photoreceptors is remarkable for its regularity, independent of lighting condition. The photosensitive microvilli of the rhabdom of small photoreceptors are narrow and almost always tightly packed in a hexagonal arrangement.In contrast, the morphology of the rhabdom of the large ventral photoreceptors is different in the dark and in the light, and the rhabdom undergoes turnover during lighting transitions. When fully dark‐adapted, the photosensitive microvilli of large photoreceptors are narrow and well organized, sometimes in a crystalline array. However, in the light‐adapted state, the microvilli are much thicker and very irregular. The transitions between the dark and light‐adapted states, examined at midday, are rapid. After 5 minutes light exposure, the microvilli are dilated at their bases and shed membranes are present in the cytoplasm. By 30 minutes after light onset, the appearance of the rhabdom of large photoreceptors is indistinguishable from fully light‐adapted cells. The transition to the dark‐adapted state is equally rapid. Even at 5 or 12 minutes after light offset, most microvilli are narrow and quite regular, and by 30 minutes, the rhabdom usually appears to be fully dark‐adapted. These experiments show that both the synthetic and degradative phases of rhabdom renewal take place in isolated photoreceptors. No efferent neural activity is required to initiate turnover; rather, changes in illumination alone are sufficient to generate rhabdom turnover in large ventral photoreceptors in vitro.
Morphological characteristics and terminating patterns of masseteric neurons of the mesencephalic trigeminal nucleus in the rat: An intracellular horseradish peroxidase labeling study
Authors: Luo P. F. , Wang B. R. , Peng Z. Z. , Li J. S. 
Published: January 2005

AbstractIn order to study the morphological characteristics and terminating patterns of the neurons of the trigeminal mesencephalic nucleus (Vme),55 masseteric neurons in Vme in the rat were stained by intracellular injection of horseradish peroxidase (HRP). Labeled cells were distributed throughout the nucleus. These neurons were divided into three types: uni‐ or pseudounipolar (type A, n = 43), bipolar (type B, n = 5), and multipolar cells (type C, n = 7). Each type was further divided into two subtypes according to the largest diameter of the perikarya (type a ≥ 30 μm, type b < 30 μm).The central processes of type Aa neurons projected to the following three groups of target nuclei: (1) nuclei functioning as interneurons, including supratrigeminal nucleus (Vsup), intertrigeminal nucleus (Vint), juxta‐trigeminal region (Vjux), and parvicellular nucleus of the pontomedullary reticular formation (PcRF); (2) motor nuclei, including the trigeminal motor nucleus (Vmo), accessory facial nucleus (NVIIacs), accessory abducens nucleus (NVIacs), and a small number of labeled axons in the oculomotor nucleus and trochlear nucleus; (3) sensory nuclei, including the dorsomedial part of the principal trigeminal sensory nucleus (Vpdm) and the dorsomedial part of subnucleus oralis of the trigeminal spinal nucleus (Vodm). Labeled processes were dense in the Vsup, Vmo, and Vpdm.The proprioceptive pathway of the fifth nerve is discussed. Direct projections from type Aa neurons of Vme to the Vpdm and dorsolateral part of the Vsup contribute to conduction of the proprioceptive information from spindles of masticatory muscle to the contralateral thalamus in the rat.Different axon morphology, distribution, terminal branch density, and terminating patterns of type Aa neurons were noted in different functional groups of the projecting nuclei, especially in the Vsup, Vmo, and Vpdm. The highest terminal branching density, the most extensive distribution, and two different types of branching patterns (claw‐like and comb‐like) were observed in Vsup. Selective distribution and single‐beaded or “Y”‐shaped terminal branches were observed in Vmo. In the Vpdm the axtinal branches were sparser than in the Vsup or Vmo, and had an arrangement like the branches of a weeping willow tree. These characteristics of anatomical organization might be related to the function of each projecting nucleus.
GABAergic circuitry in the rostral ventral medulla of the rat and its relationship to descending antinociceptive controls
Authors: Cho Hee Jung , Basbaum Allan I. 
Published: January 2005

AbstractThis study used postembedding immunocytochemistry to examine the organization of GABA‐immunoreactive synapses in the rostral ventral medulla (RVM) of the rat. To determine whether the outflow neurons of the RVM are under GABAergic control, we examined the distribution of GABA‐immunoreactive synapses upon bulbospinal projection neurons that were labelled by retrograde transport of wheatgerm agglutinin‐HRP from the cervical spinal cord. To study the possible convergence of GABAergic and periaqueductal gray (PAG) synaptic inputs to RVM neurons, we also made lesions in the PAG and examined the relationship between degenerating PAG axons and GABA‐immunoreactive terminals.Approximately 45% of all synapses in the RVM, which includes the midline nucleus raphe magnus and the nucleus reticularis paragigantocellularis lateralis, were GABA‐immunoreactive. The vast majority of GABA‐immunoreactive terminals contained round, clear, and pleomorphic vesicles and made symmetrical axodendritic synapses; axoaxonic synapses were not found. Almost 50% of the retrogradely labeled dendrites in the NRM were postsynaptic to GABA‐immunoreactive terminals. Several examples of convergence of degenerating PAG terminals and GABAergic terminals onto the same unlabelled dendrite were also found. These data indicate that the projection neurons of the RVM are urider profound GABAergic inhibitory control. The results are discussed with regard to the hypothesis that the analgesic action of narcotics and electrical stimulation of the midbrain PAG involves the regulation of tonic GABAergic inhibitory controls that are exerted upon spinally‐projecting neurons of the nucleus raphe magnus.
“Sunbursts” in the inner plexiform layer: A spectacular feature of Müller cells in the retina of the cat
Authors: Stone Jonathan , Holläunder Horstmar , Dreher Zofia 
Published: January 2005

AbstractA previously unrecognised structure in the cat retina is described. Seen in Golgi‐impregnated, wholemounted retinas, each such structure comprises processes radiating across the inner plexiform layer from a dense, vellate core. The processes are numerous, and largely unbranched, and give the impression of rays radiating from a point source; the structure is therefore termed a “sunburst.” Evidence is presented from Golgi‐impregnated retinas, and from retinas labelled with monoclonal antibodies to Müller cells, that the core of each sunburst is the inner process of a Müller cell. The sunbursts are numerous and overlap extensively, so that when neighbouring sunbursts are impregnated, they are seen to form a dense mat of processes extending across the IPL. It is suggested that each Müller cell forms a sunburst and that sunbursts form a major glial component of the neuropil of the inner plexiform layer.
Comparative analysis of dopamine and tyrosine hydroxylase immunoreactivities in the brain of two amphibians, the anuran Rana ridibunda and the urodele Pleurodeles waltlii
Authors: Gonzalez Agustin , Smeets Wilhelmus J. A. J. 
Published: January 2005

AbstractTo gain more insight into the dopaminergic system of amphibians and the evolution of catecholaminergic systems in vertebrates in general, the distribution of dopamine and tyrosine hydroxylase immunoreactivity was studied in the brains of the anuran Rana ridibunda and the urodele Pleurodeles waltlii. In both species, dopamine‐immunoreactive (DAi) cell bodies were observed in the olfactory bulb, the preoptic area, the suprachiasmatic nucleus, the nucleus of the periventricular organ and its accompanying cells, the nucleus of the posterior tubercle, the pretectal area, the midbrain tegmentum, around the solitary tract, in the ependymal and subependymal layers along the midline of the caudal rhombencephalon, and ventral to the central canal of the spinal cord. Tyrosine hydroxylase (TH) immunohistochemistry revealed a similar pattern, although some differences were noted. For example, with the TH antibodies, additional cell bodies were stained in the internal granular layer of the olfactory bulb and in the isthmal region, whereas the same antibodies failed to stain the liquor contacting cells in the nucleus of the periventricular organ.Both antisera revealed an almost identical distribution of fibers in the two amphibian species. Remarkable differences were observed in the forebrain. Whereas the nucleus accumbens in Rana contains the densest DAi plexus, in Pleurodeles the dopaminergic innervation of the striatum prevails. Moreover, cortical structures of the newt contain numerous DAi fibers, whereas the corresponding structures in the frog are devoid of immunoreactivity. The dopaminergic system in amphibians appears to share many features not only with other anamniotes but also with amniotes.
Organization of motor units in the axolotl: A continuously growing animal
Authors: Bewick G. S. , Rowlerson A. , Tonge D. A. , Holder Nigel 
Published: January 2005

AbstractThe characteristics of motor units in the iliotibialis posterior muscle of the axolotl hindlimb are described. Tension recording and intracellular electrophysiological methods demonstrate that the physiological properties of the population of motor units are continuously distributed rather than grouped into a series of discrete types. Overlap between motor units occurs and this is positively correlated with motor unit size but negatively correlated with differences in time to peak tension. Immunocytochemical staining with antimyosin antibodies combined with histochemical demonstration of actomyosin ATPase activity revealed at least four types of muscle fibre which were distributed asymmetrically within iliotibialis posterior. The results are discussed in terms of the continuous growth of the muscle and the interactions between muscle and nerve in the formation of the axolotl motor system.
Trajectory of spinocerebellar fibers passing through the inferior and superior cerebellar peduncles in the rat spinal cord: A study using horseradish peroxidase with pedunculotomy
Authors: Yamada Jinzo , Shirao Kuniaki , Kitamura Taiko , Sato Hitoshi 
Published: January 2005

AbstractThe course of spinocerebellar fibers in the rat spinal cord was investigated by injecting horseradish peroxidase into the cerebellar anterior vermis after complete transection of the left inferior and right superior cerebellar peduncles. By this procedure, fibers passing via the inferior cerebellar peduncles (icp‐fibers) were labeled retrogradely on the right side of the spinal cord, whereas fibers passing via the superior cerebellar peduncles (scp‐fibers) were labeled on the left side. Crossed icp‐fibers were located diffusely in the anterior and lateral funiculi in the sacral to lower lumbar segments. They gradually migrated laterally and dorsally in these funiculi and received many uncrossed icp‐fibers moving laterally in the lateral funiculus from the gray substance in the upper lumbar to lower thoracic segments. These mixed fibers shifted more dorsally and laterally in the anterior and lateral funiculi to aggregate in the narrow peripheral zone of the lateral funiculus in the upper thoracic and lower cervical segments, and received many crossed fibers in the upper cervical segments. There were more icp‐fibers than scp‐fibers through the spinal cord. However, the extent of scp‐fibers in the anterior and lateral funiculi was essentially the same as that for icp‐fibers, except that a few scp‐fibers were found in the dorsolateral marginal zone of the lateral funiculus. It has been generally accepted that the dorsal spinocerebellar tract ascends in the dorsal half of the lateral funiculus and enters the cerebellum via the inferior cerebellar peduncle, whereas the ventral spinocerebellar tract ascends in the ventral half of it and takes the superior cerebellar peduncle route. The results of this study suggest that it is necessary to revise this concept.
The reticular thalamic nucleus (RTN) of the rat: Cytoarchitectural, Golgi, immunocytochemical, and horseradish peroxidase study
Authors: Spreafico R. , Battaglia G. , Frassoni C. 
Published: January 2005

AbstractExperiments have been performed on adult albino rats in order to study the cellular organization of the thalamic reticular nucleus. For this purpose four approaches have been used: Nissl stain, Golgi impregnation, retrograde transport of horseradish peroxidase after injection in different thalamic nuclei, and immunocytochemistry with antibodies against GABA and glutamic acid decarboxylase. In sections through the horizontal plane, three morphologically different neurons have been observed. Cells with round perikarya and with multipolar dendrites were found predominantly in the rostral pole of the nucleus. Neurons with large fusiform cell body and with dendrites arborizing mainly on the horizontal plane were detected through the whole extent of the nucleus. Small fusiform neurons were observed almost exclusively in the medial third of the dorso‐ventral extent of the nucleus. The Golgi impregnation method demonstrated that dendrites of small fusiform neurons develop in the vertical plane perpendicular to the dendritic arborization of large fusiform neurons. In coronal sections neurons with round perikarya and with large fusiform cell bodies are detectable while small fusiform neurons are only rarely visible. These data have been confirmed by statistical form factor analysis. Moreover, by means of the horseradish peroxidase and the immunocytochemical study, it has been confirmed that all three groups of neurons project within the thalamus and that they are GABAergic. The data concerning the distribution within the nucleus of the three morphologically different neurons are discussed in relation to the topographic distribution of cortical sensory afferents and to the topographic maps within different sectors of the reticular nucleus.
Laminar and regional distribution of galanin binding sites in cat and monkey visual cortex determined by in vitro receptor autoradiography
Authors: Rosier A. M. , Vandesande F. , Orban G. A. 
Published: January 2005

AbstractThe distribution of galanin (GAL) binding sites in the visual cortex of cat and monkey was determined by autoradiographic visualization of [125I]‐GAL binding to tissue sections. Binding conditions were optimized and, as a result, the binding was saturable and specific. In cat visual cortex, GAL binding sites were concentrated in layers I, IVc, V, and VI. Areas 17, 18, and 19 exhibited a similar distribution pattern. In monkey primary visual cortex, the highest density of GAL binding sites was observed in layers II/III, lower IVc, and upper V. Layers IVA and VI contained moderate numbers of GAL binding sites, while layer I and the remaining parts of layer IV displayed the lowest density. In monkey secondary visual cortex, GAL binding sites were mainly concentrated in layers V–VI. Layer IV exhibited a moderate density, while the supragranular layers contained the lowest proportion of GAL binding sites. In both cat and monkey, we found little difference between regions subserving central and those subserving peripheral vision. Similarities in the distribution of GAL and acetylcholine binding sites are discussed.
Basic FGF‐like immunoreactivity in the developing and adult rat brainstem
Authors: Grothe Claudia , Zachmann Karolin , Unsicker Klaus 
Published: January 2005

AbstractAlthough a variety of in vitro and in vivo actions of basic fibroblast growth factor (bFGF) on neuronal cells have been documented, the physiological role of this protein in the nervous system is still contested. Since the distribution of a molecule in the nervous system may provide cues for an understanding of its possible roles, we have begun to study its cellular localization in the central and peripheral nervous system using immunocytochemistry with an anti‐bFGF‐specific antibody. Here we provide an account on the distribution of bFGF‐like immunoreactivity (bFGF‐IR) in the brainstem of the developing and adult rat. Basic FGF‐IR was found to be widely distributed in motor and sensory nuclei. In all nuclei examined, only subpopulations of neurons were stained. Different staining patterns were found. For example, in the red nucleus weakly or unstained perikarya were surrounded by numerous immunoreactive fibers, often in close contact with the neuronal surface. In the reticular formation and facial nerve, many neuronal cell bodies showed a strong IR that extended into the processes. Glial cells were consistently unstained. During early postnatal development changes of the distribution of bFGF IR were found. From this wide distribution pattern of bFGF‐IR, we conclude that bFGF may have more general and, possibly, diverse functions rather than a restricted role for a particular subset of neurons. Variations in the staining pattern of nerve cell bodies in a single nucleus may suggest a function related to neuronal activity.
Somatosensory cortex of the neonatal pig: I. Topographic organization of the primary somatosensory cortex (SI)
Authors: Craner Sandra L. , Ray Richard H. 
Published: January 2005

AbstractThe cerebral cortex of adult mammals contains several somatotopic representations of the body surface. Although the organization of the various somatosensory cortices of numerous species of adult animals has been elucidated, data on the somatosensory representations of fetal and neonatal animals are limited. As part of an investigation into the perinatal development of the somatosensory cortices, it was necessary to delineate the organization of the somatosensory cortices of the perinatal pig. This study presents the topographical organization of the primary somatosensory cortex (SI) of the perinatal pig.Multiunit microelectrode mapping methods were used to produce topographic maps of SI from barbiturate anesthetized pigs ranging in age from 7 days preterm to 2 months postpartum. It was demonstrated that the overall organization of this region of cortex was similar to that of other mammals: a somatotopic projection of predominantly the contralateral body surface was delineated in which the hindlimb is represented medially and the face laterally across the cortex. A disproportionately enlarged rostrum representation was mapped in detail, and multiple representations of the rostrum, face, and mouth were found. Several of these representations exhibited bilateral and ipsilateral input. The SI trunk and hindlimb representations were located on the medial wall of the hemisphere; these representations were small but their presence refutes speculation that ungulates do not have a complete body representation in SI.