bluuebunny/crossref_metadata_2025 huggingface dataset:
The localization of cytochrome oxidase in the LGN and striate cortex of postnatal kittens
Authors: Kageyama Glenn H. , Wong‐Riley Margaret
Published: January 2005

The distribution of cytochrome oxidase (C.O.) was examined in the lateral geniculate nucleus of the kitten during the first postnatal month and compared with the adult pattern. During the first week, most of the C.O. was localized within the perikarya of geniculate neurons. Perigeniculate neurons had darkly reactive dendrites as well as perikaya. A population of relatively large, darkly reactive neurons became distinguishable around the end of the first week, as the level of reactivity diminished to moderate‐to‐light within most medium and small neurons. On the basis of their relative size and pattern of distribution, most of the darkly reactive neurons are likely to represent ones that will later have class 1 morphology and develop Y receptive field properties. These cells normally undergo rapid growth earlier, and their growth is more adversely affected by early short‐term monocular suture than other classes of less reactive geniculate neurons. Thus, in the LGN of developing kitten, C.O. histochemistry may be used as a functional marker for future class 1 Y‐cells. The reactivity of the neuropil gradually increases as synapses with dendrites mature. At the electron‐microscopic level the increased reactivity of the neuropil is due mainly to an increase in the number of reactive mitochondria localized within the growing dendrites.

In the developing striate cortex of postnatal kittens dark reactivity is localized in the outer part of layer II for the first 2 weeks and then disappears. Dark reactivity gradually increases in layer IV after the third week. The changes in C.O. reactivity accompany pathway‐specific physiological and anatomical changes that occur during early postnatal development.
Body surface maps in the somatosensory cortex of rabbit
Authors: Gould Harry J.
Published: January 2005

The organization of somatosensory maps was examined in rabbits with the aid of microelectrode multi‐unit recording techniques. Two complete maps of the contralateral body surface are identified in the parietal cortex. The first map, S I, is found entirely on the lateral convexity of the hemisphere and closely resembles S I described in the rat (Welker, '71, '76). It is organized in a complex, though systematic, fashion with the representations of the hindlimb and tail located caudomedially. These representations are followed laterally in sequence by those of the trunk and forelimb and then the representation of the head. Within the head representation the lips are found rostrally, the vibrissae caudomedially, and the displaced representation of the pinna of the ear is located caudolaterally. Unlike the disposition in most other mammals, the dorsal midline of the trunk is represented along the caudal border of S I. Within S I, the representations of the circumoral surfaces, including the lips, philtrum, nose, and vibrissae, are emphasized, occupying approximately 86.4% of the map. It is suggested that S I is contained within a single major koniocortical region, here called the medial parietal area, or Pm. The several previously described parietal regions (Rose, '31; Fleischhauer et al., '80) are interpreted as subregions that are related to particular representations of portions of the body surface.

The second map, S II, is located lateral to S I in a region here called the lateral parietal area or Pl. S II shares a common border with S I along the representations of the philtrum, bridge of the nose, and top of the head. The body is oriented in an erect conformation with the head located rostrally and medially and the hindlimb and tail located caudally and laterally.
Morphology and physiology of abducens motoneurons and internuclear neurons intracellularly injected with horseradish peroxidase in alert squirrel monkeys
Authors: McCrea R. A. , Strassman A. , Highstein S. M.
Published: January 2005

Axons of abducens motoneurons and internuclear neurons were penetrated with HRP‐filled glass microelectrodes in alert squirrel monkeys. The firing rate of these axons and spontaneous eye movements were recorded and the axons were then injected with HRP for subsequent visualization of the recorded cells. Soma‐dendritic and axon and axonal terminal morphology were studied for possible correlation with firing frequency. The physiology of squirrel monkey abducens neurons is qualitatively similar to their counterparts in the rhesus monkey and the cat, being primarily correlated with the position and velocity of the eyes. The locations of moto‐ and internuclear neurons are similar in the squirrel monkey and cat as are the axonal projections and terminals. However, squirrel monkey abducens cells are smaller than their feline counterparts and have dendrites that are confined to the cellular borders of the abducens nucleus. The size of the soma and proximal dendrites of moto‐ and internuclear neurons are poorly correlated with either their threshold for recruitment or their tonic eye position sensitivity. However, cells with smaller dendritic trees tended to have higher saccadic eye velocity sensitivity than those with larger trees. Three types of internuclear neurons were distinguishable upon the basis of their axon collaterals. All cells terminated within the medial rectus subdivision of the oculomotor nucleus. One class of cells did not give rise to collaterals before projecting to the oculomotor nucleus and the other classes gave rise to collaterals that terminated in the intermediate and/or caudal interstitial nuclei of the median longitudinal fasciculus. Within the IIIrd nucleus internuclear terminations were usually confined to a single subgroup of medial rectus motoneurons.
Are there connections between the thalamic reticular nucleus and the brainstem reticular formation?
Authors: Berry D. J. , Ohara P. T. , Jeffery G. , Lieberman A. R.
Published: January 2005

Increasing awareness that the thalamic reticular nucleus (TRN) plays an important role in controlling the output of cortically projecting cells in nuclei of the dorsal thalamus has focused attention on the question of whether there exist ascending projections to the TRN from the mesencephalic or other parts of the brainstem reticular formation (BRF). We have examined this and the related question of whether the neurons of TRN project to the BRF, by anterograde and retrograde tracing experiments with horseradish peroxidase (HRP) and HRP conjugated to wheat germ agglutinin. Injections of tracer were placed stereotaxically in the BRF at various depths and rostrocaudal and mediolateral coordinates, and the TRN and adjacent nuclei were examined in serial coronal sections, using tetramethylbenzidine as the principal chromogen.

Retrogradely labelled cell bodies were consistently seen in hypothalamus and zona incerta but never in TRN, suggesting that, in the rat, TRN neurons do not project caudal to the thalamus.

After 54 out of 60 injections, no terminal label was detected in any part of the TRN although such label was present in other parts of the thalamus, including the intralaminar nuclei, in the same sections. We therefore conclude that direct projections from the BRF to the TRN must be extremely sparse, and that those effects of BRF stimulation upon thalamocortical transmission that are mediated by the TRN (rather than by direct projections to dorsal thalamic nuclei) probably depend chiefly on indirect polysynaptic pathways.
Regional specialization of the rat retina: Catecholamine‐containing amacrine cell characterization and distribution
Authors: Versaux‐Botteri C. , Martin‐Martinelli E. , Nguyen‐Legros J. , Geffard M. , Vigny A. , Denoroy L.
Published: January 2005

The distribution of catecholaminergic amacrine cells has been investigated in rats by means of immunohistochemical labelling of wholemounted retinas. Two groups of catecholamine‐containing cells could be distinguished on the basis of their catecholamine and biosynthetic enzyme content. Both groups could be stained with an anti–tyrosine hydroxylase (TH) antiserum. The first group was composed of large, strongly TH‐immunoreactive stellate amacrine cells, located principally in the innermost row of the inner nuclear layer (INL) and sending processes to the outermost sublamina of the inner plexiform layer (IPL). Some were displaced in the IPL or in the ganglion cell layer (GCL). This first group of cells can be regarded as dopaminergic since they were also stained by an anti‐dopamine (DA) antiserum. The second group was composed of small, weakly TH‐positive cell bodies, located slightly more sclerad within the INL. Their processes were usually not labelled with anti‐TH. Identical cells could be better visualized with an anti‐phenylethanolamine‐N‐methyltransferase (PNMT) antiserum. Their processes were observed in the middle sublamina of the IPL. A great number of these cells were displaced in the GCL. They could be regarded as epinephrine cells.

Concerning the density and distribution throughout the retina a striking difference was observed between the superior and inferior halves of the retina, whereas a lower difference was observed between the nasal and temporal regions. Almost all the PNMT‐immunoreactive cells were located throughout the upper retina, whereas the DA‐cells were especially concentrated in the upper temporal quadrant. The distribution of the DA cells parallels that of the ganglion cells whose density is also maximal in the upper temporal retina.
Cortical projections originating from the cat's insular area and remarks on claustrocortical connections
Authors: Guldin Wolfgang O. , Markowitsch Hans J. , Lampe Regina , Irle Eva
Published: January 2005

The cortical projections originating in the cat's insular cortex and claustrum were investigated with the aid of the horseradish peroxidase retrograde tracing technique. Twenty small injections of horseradish peroxidase were distributed along lateral and medial regions of the hemisphere. Labeling in the insular cortex occurred following all injections except those six situated along the lateral gyrus–that is, within the visual cortex.

In the claustrum labeled neurons were found following all injections, except following the injection situated in the posterior temporal area. Claustral labeling was frequently more intense than insular labeling. The injections into the occipital cortex that revealed no insular innervation nevertheless received a considerable number of claustral projections. As the insular cortex itself receives at most a minor projection from the claustrum the differing cortical projection patterns of insula and claustrum have to be considered unrelated.

Our findings confirm the view that the claustrum projects to most regions of the cerebral cortex; these projections are at least in part topographically organized. A topographical pattern can also be constructed for the insular cortex, though it is less stringent than for the claustrocortical connections.

Both the afferent and efferent connections of the insula show similarities to those of the prefrontal cortex. Nevertheless, the insula differs in that it receives strong input from the sensory associative nuclei of the thalamus. Consequently, and in line with behavioral observations following its ablation, we consider the insula as involved in the temporal structuring of perceived patterns.
Mechanosensory appendages and giant interneurons in the firebrat (Thermobia domestica, thysanura): A prototype system for terrestrial predator evasion
Authors: Edwards John S. , Rajarami Reddy G.
Published: January 2005

Aspects of the structure and function of the abdominal cerci and caudal filament sensory systems, and associated giant interneurons of the thysanuran insect Thermobia domestica, the firebrat, extend comparative studies of a widespread predator evasion system. All elements of the cercal system, which is well known from diverse orthopteroid insects, are present in the primitively wingless thysanuran. In addition, a median terminal sensory appendage, the caudal filament, projects to the same general regions of the terminal ganglion but shows limited overlap of synaptic regions with cercal input. A segmental series of giant interneurons appears to be homologous with those of the orthopteroid insects. The cercal system, which may have evolved with the first terrestrial hexapods, reaches its zenith in the orthopteroid insects, but was replaced in holometabolan insects by visual startle mechanisms with descending giant interneurons.
The early development of the optic nerve and chiasm in embryonic rat
Authors: Horsburgh Gwynn M. , Sefton Ann Jervie
Published: January 2005

To establish the time course and major features of the development of the optic nerve and chiasm in the embryonic rat, the growth of axons from the retina to the brain has been studied by light and electron microscopy. On embryonic dy 14 (E14), the first axons are generated by retinal ganglion cells. Fascicles of axons can be detected in the‐optic stalk at E14.5 and in the diencephalon by E15.0. In the vitreal retina and optic fissure, large extracellular spaces resemble the oriented channels previously described in the mouse. They form approximately 12 hours before the invasion of optic axons and contain hyaluronic acid. In the optic stalk and diencephalon of the rat, similar spaces are not present, but the timed autolysis of neuroepithelial cells could provide a pathway of minimal resistance for the earliest axons. Degenerating cells are prominent in the ventral stalk and rostral diencephalon prior to the arrival of the first optic axons that preferentially invade these regions. The role of pigment in the development of visual pathways is controversial. In one strain of rat, Manchester Hooded, the retinae are heavily pigmented, but little pigment is seen at any stage in the stalk; in albinos, pigment is absent from both retina and stalk. However, the distribution of axons within the developing optic stalk is very similar in both strains, suggesting that the reduction in size of the ipsilateral pathway observed in the albino rat compared with the Manchester Hooded is not due to a lack of pigment in the optic stalk early in development. Several factors previously reported to contribute to the development of retinotopic order in other species are also present in the rat. These include the sequence in which axons grow into the stalk, and fasciculation. Intermembranous contacts observed between growth cones and adjacent tissues suggest one mechanism by which fasciculation occurs. A small group of fascicles, which may represent the ipsilateral projection, diverges from the crossing fibers on E15.5, without evidence of being deflected by any glial or other structures.
Anatomy of the gustatory system in the hamster: Synaptology of facial afferent terminals in the solitary nucleus
Authors: Whitehead Mark C.
Published: January 2005

The solitary nucleus is the first level of the central nervous system where processing of taste information can occur. A structural basis for that processing was investigated. Facial taste afferent axons were labelled by application of horseradish peroxidase to either the chorda tympani or the geniculate ganglion. The labelled afferent fibers in the rostral solitary nucleus were studied with light and electron microscopy. Preterminal facial taste afferent axons enter the nucleus from the solitary tract with a pronounced lateral to medial trajectory. The axons bear numerous preterminal and terminal swellings that, with the electron microscope, were identified as synaptic endings located in glomeruli. The endings are ovoid or scalloped, indented by structures that surround them. The primary afferent endings contain large, round vesicles and synapse, by means of slightly asymmetrical junctional complexes, on small dendrites and spines. Two types of unlabelled endings, surrounding the labelled ones, contact the dendrites receiving taste afferent input or contact the endings of taste afferent axons themselves. One type is variable in size and contains scattered large round vesicles. It resembles a presynaptic dendrite. The other is a small axonal ending packed with small, pleomorphic vesicles, that engages in symmetrical junctions. The synaptic milieu of the taste endings allows for the possibility of modulation of taste‐elicited activity in afferent endings or secondorder neurons by other, possibly interneuronal, inputs.
A comparative topographical analysis of dorsal column nuclear and cerebral cortical projections to the basilar pontine gray in rats
Authors: Kosinski Ross J. , Neafsey E. J. , Castro Anthony J.
Published: January 2005

The somatotopic distribution of dorsal column nuclear projections within the basilar pontine gray was examined in relation to the massive corticopontine projection system that emanates most heavily from motor and somatosensory cortex. The distribution patterns of these two systems were compared by combining autoradiographic and degeneration axonal tracing methods within individual animals.

Sterentaxic injections of tritiated leucine (50 μCi/μl) and lesions by aspiration were made in animals under ketamine hydrochloride anesthesia. The forelimb cortical injections (0.1–0.3 μl) were centered in either sensory or motor cortical regions as determined by intracortical microstimulation and multiunit recording techniques. Because sensory and motor hindlimb cortical areas overlap extensively in the rat, hindlimb cortical injections (0.1–0.3 μl) were limited to a single hindlimb sensorimotor cortical region. The corresponding contralateral dorsal column nucleus, cuneatus or gracilis, was then aspirated.

A somatotopic distribution of fore‐ and hindlimb corticopontine fibers were found in discrete regions of the ipsilateral pontine gray. Hindlimb sensorimotor corticopontine fibers distributed caudal to forelimb projections. Similarly, pontine afferents from the dorsal column nuclei terminated somatotopically in the caudal half of the contralateral pontine gray in that gracilopontine fibers distributed caudal to cuneopontine fibers. Within individual animals, partially overlapping terminations were seen from nucleus cuneatus and the forelimb sensory cortical area as well as from nucleus gracilis and the hindlimb sensorimotor cortical area. No overlap existed in the pontine terminations from nucleus cuneatus and the forelimb motor cortical area.
Somatostatinlike immunoreactive neurons in the hedgehog (Erinaceus europaeus) and the sheep (Ovis aries) central nervous system
Authors: Papadopoulos G. C. , Karamanlidis A. N. , Dinopoulos A. , Antonopoulos J.
Published: January 2005

The morphology and distribution of somatostatinlike immunoreactive perikarya in the central nervous system of the hedgehog and sheep have been studied by means of the peroxidase‐antiperoxidase immunohistochemical method. Intracerebroventricular colchicine infusion not only enhanced the immunostaining but also revealed new immunoreactive cell bodies. In both hedgehog and sheep immunoreactive neurons of various forms, ranging from 12 to 28 μm in diameter, were observed in a number of homologous brain structures. However, some species‐related differences were noticed. Thus, somatostatinlike immunoreactive neurons were found only in the hedgehog anterior olfactory nucleus, olfactory tubercle, nucleus accumbens, medial parabrachial nucleus, raphe nuclei of the medulla, and spinal trigeminal nucleus, whereas some somatostatin‐positive neurons were observed in the locus coeruleus and the pontine reticular formation of the sheep only.

Mapping of peptides in species like sheep and hedgehog, with basically different orientations of living behaviour, may contribute in strengthening or extending our views concerning the role of peptides in the central nervous system of mammals.
Electrophysiological and morphological correlates of axotomy‐induced deafferentation of the goldfish mauthner cell
Authors: Wood Malcolm R. , Faber Donald S.
Published: January 2005

Axotomy‐induced changes in afferent synapses to the goldfish Mauthner cell have been analyzed with intracellular recordings and with electron microscopy. The studies encompassed 7–208 days after cervical spinal cord transection. The physiological findings suggest a persistent and specific reduction in excitatory chemical inputs to the soma and proximal lateral dendrite, with no changes in somatic inhibition or in the electrotonic and chemical inputs to the more distal regions of the lateral dendrite. Corroborative morphological evidence includes swelling of the M‐cell soma, as indicated by a 35% increase in the length of its minor diameter, an increased spacing and a quantitatively lower density of terminals on the soma, and the appearance of astrocytic processes partially or completely engulfing the terminals in that region. Similar changes were observed on the inferior dendrites projecting from the ventral surface of the soma, although these dendrites do not exhibit the chromatolytic changes observed at the soma. In contrast, there are no noticeable changes in either the synaptic investment of the lateral dendrite or its ultrastructure. Quantitative and qualitative data support the conclusion that there is a restricted and specific reduction in the proximal excitatory inputs to the M‐cell. The evidence also suggests that electrotonic junctions between afferents and the M‐cell remain intact, functionally and structurally.
Origin and identification of fibers in the cranial nerve IX‐X complex of xenopus laevis: Lucifer yellow backfills in vitro
Authors: Simpson H. Blair , Tobias Martha L. , Kelley Darcy B.
Published: January 2005

The central projections of individual components of the IX‐X nerve complex in the South African clawed frog, Xenopus laevis, were mapped by dye diffusion with Lucifer Yellow in an isolated brain preparation. The method reliably revealed fiber tracts, termination zones, and detailed cell morphology. In addition, motor neurons could be doubly labelled by retrograde transport of horseradish peroxidase from muscle targets followed by backfilling the appropriate nerves with Lucifer Yellow. The most anterior root associated with the nerve IX‐X complex, root 1, is composed of lateral line afferents that terminate in the medial medulla. Root 2 contains sensory fibers that terminate in the nucleus tractus solitarii and axons of lateral line efferent neurons. Root 3 is composed of sensory and motor fibers, including a major somatosensory component that terminates in posterior medulla and anterior spinal cord, and axons from cranial nerve nucleus IX‐X. The most posterior root of the IX‐X nerve complex, root 4, contains axons of laryngeal motor neurons and of general visceral efferent neurons.
Immunocytochemical demonstration of topographic ordering of purkinje cell axon terminals in the fastigial nuclei of the rat
Authors: Hawkes Richard , Leclerc Nicole
Published: January 2005

We have used a monoclonal antibody, mabQ113, which selectively stains a subset of cerebellar Purkinje cells, to study the topography of the corticonuclear projection of the median vermis to the fastigial nuclei in the rat. The fastigial projection zone contains both mabQ113+ and mabQ113− Purkinje cells grouped into parasagittal bands. The immunoreactivity extends throughout the Purkinje cell including the axon terminals and thus it is possible to investigate the topographic distribution of mabQ113+ terminals. In the fastigial nuclei the target cells receiving mabQ113+ axon terminals are concentrated in the caudal pole. In the rostral pole, cells receive anti‐GAD+ terminals but not mabQ113+ terminals. There is no gradient in anti‐GAD staining. Double‐labelling experiments with mabQ113, anti‐GAD, and an antisynaptic antibody mabQ155 suggest that there is little or no mixing of mabQ113+ and mabQ113− Purkinje cell terminals on the same target neuron.
The organization of prefrontocaudate projections and their laminar origin in the macaque monkey: A retrograde study using HRP‐gel
Authors: Arikuni Tomio , Kubota Kisou
Published: January 2005

The organization of the prefrontocaudate connection in the macaque monkey was studied with a polyacrylamide gel of horseradish peroxidase that was injected, after callosotomy, into the head of the caudate nucleus. Tissues were processed for peroxidase activity with tetramethylbenzidine. Retrogradely labeled cells appeared bilaterally in the prefrontal cortex, and ipsilaterally in the premotor area, frontal operculum, insula, and rostral region of the temporal cortex. In the prefrontal cortex, labeled cells were located in cortical layers 2–6. In layer 2, labeled cells were occasionally seen. In layer 3, a considerable number of labeled cells were seen and were mainly distributed in its lower part. They were pyramidal cells. Layer 4 contained a considerable number of labeled cells that were pyramidal or round. Somal sizes of these labeled cells were from 5 to 15 μm, but none of the cells less than 5 μm were labeled. Layer 5 was densely packed with labeled cells, though at a higher density in its upper part (5a). They were pyramidal cells. In layer 6, pyramidal or fusiform cells were labeled at a lower density than in layer 5. The laminar pattern and density of labeled cells were different among various regions of the prefrontal cortex, but, in general, the supragranular labeling tended to frequently occur in the regions containing the numerous labeled cells. There was a topographical relationship between the prefrontal regions containing the majority of labeled cells and the injection sites in the head of the caudate nucleus: the medial orbitofrontal cortex and the medial surface extending downward from the rostral sulcus project ipsilaterally to the medialmost portion of the ventromedial part of the head of the nucleus, the lateral orbitofrontal cortex projects to the ventromedial part of the head of the nucleus, and the dorsolateral prefrontal cortex ventral to the principal sulcus projects to the central part of the head of the nucleus. Our findings in the macaque monkey indicate that the corticocaudate connection is similar in laminar organization of efferent neurons to the corticocortical connections.
Afferent and efferent connections of cerebellar lobe C1 of the mormyrid fish Gnathonemus petersi: An HRP study
Authors: Meek J. , Nieuwenhuys R. , Elsevier D.
Published: January 2005

The corpus of the highly developed cerebellum of the weakly electric fish Gnathonemus petersi is differentiated into four lobes, numbered C1 to C4. The present paper deals with the extrinsic connections of the rostralmost lobe C1. Relevant nuclei were studied in normal histological material and HRP injections were placed in lobe C1, the neighbouring pedunculus valvulae, and the brainstem.

The largest number of afferents to lobe C1 originates from the nucleus lateralis valvulae, a large nucleus of tightly packed small cells in the dorsal midbrain tegmentum. In Gnathonemus this nucleus encompasses nine subdivisions, of which the rostral, caudal, and exterolateral parts project in particular to lobe C1. Larger neurons in the dorsal midbrain tegmentum and presumed mesencephalic trigeminal neurons project to C1 as well. In the rhombencephalon, afferents to lobe C1 arise from the first funicular nucleus, the lateral reticular nucleus, and the inferior olive.

Efferents of lobe C1 have been found to arise from a peculiar cell type in the Purkinje cell layer (so‐called eurydendroid neurons) and to project predominantly to the nucleus of the fasciculus longitudinalis medialis, the nucleus reticularis superius and medius, and the trigeminal motor nucleus. Additional small projections terminate in the tectum mesencephali and in the nucleus reticularis inferior.

Compared with other parts of the mormyrid cerebellum as well as with the cerebellum of other teleosts, the connections of lobe C1 appear to be quite restricted and specialized. In this respect the connections with the trigeminal nerve via the first funicular nucleus, the mesencephalic trigeminal nucleus, and the trigeminal motor nucleus are of particular interest. The absence of central cerebellar nuclei intercalated in the efferent cerebellar connections, in combination with the presence of a precerebellar nucleus (lateralis valvulae) involved in the afferent cerebellar connections, represents a remarkable difference between teleosts and other vertebrate classes.
Biochemical and morphological correlates of transmitter type in C2, an identified histaminergic neuron in Aplysia
Authors: Schwartz James H. , Elste Alice , Shapiro Eli , Gotoh Hideki
Published: January 2005

There is compelling evidence that histamine serves as a neurotransmitter in C2, a pair of symmetrical neurons in the cerebral ganglion of Aplysia californica. These cells had previously been shown to contain high concentrations both of histamine and of its biosynthetic enzyme, histidine decarboxylase; in addition, 3H‐histamine injected intrasomatically was found to move along C2's axons by fast transport. Furthermore, several actions of C2 on identified follower cells were simulated by the application of histamine. We have now characterized this identified neuron further. C2 converts 3H‐histidine to histamine: 16% of the labeled precursor was converted to histamine 1 hour after intrasomatic injection. Synthesis of 3H‐histamine is specific, since no conversion occurred after injection of other identified Aplysia neurons that are known to use other neurotransmitter substances.

We also examined the fine structure of C2's cell body, axons, and axon terminals within the cerebral ganglion and in the nerves that carry its three peripheral branches, identified after injection of Lucifer Yellow, 3H‐histamine, or horseradish peroxidase. Characteristic dense‐core vesicles are present in all regions of the neuron, and are labeled after intrasomatic injection of 3H‐histamine. These 100‐nm vesicles together with 60‐rim electron‐lucent vesicles fill the varicose extensions of C2's neurites that are widely distributed within the ganglion, but only the smaller vesicles cluster at the membrane specializations presumed to be active zones that make contact with many neurons. The widespread distribution of axon terminals and varicosities is consistent with the idea that C2 is modulatory in function; 3H‐histamine is taken up selectively by the cell body and axons of C2 and of several other putative histaminergic neurons in a Na+‐dependent manner. Characterization of these biochemical and morphological features of C2 adds to the large amount of information already available to make this identified cell a standard for identifying other neurons that use histamine as a transmitter.
Optic tectum of the eastern garter snake, Thamnophis sirtalis. V. Morphology of brainstem afferents and general discussion
Authors: Dacey Dennis M. , Ulinski Philip S.
Published: January 2005

Brainstem neurons that project to the optic tectum of the eastern garter snake were identified by retrograde transport of horseradish peroxidase. The distribution and morphology of tectal afferent axons from the thalamus, pretectum, nucleus isthmi, and midbrain reticular formation were then studied by anterograde transport of horseradish peroxidase.

Diencephalic projections to the tectum arise from the ventral lateral geniculate complex ipsilaterally and the ventrolateral nucleus, suprapeduncular nucleus, and nucleus of the ventral supraoptic decussation bilaterally. Three pretectal groups (the lentiform thalamic nucleus, the lentiform mesencephalic‐pretectal complex and the geniculate pretectal nucleus) give rise to heavy, bilateral tectal projections. Small neurons in nucleus isthmi and large reticular neurons in nucleus lateralis profundus mesencephali also give rise to bilateral projections. Caudal to the tectum, projections arise bilaterally from the pontine and medullary tegmentum, nuclei of the lateral lemniscus, the posterior colliculus, and the sensory trigeminal nucleus. A small contralateral projection arises from the medial vestibular complex.

Tectal afferents from the thalamus, pretectum, nucleus isthmi, and midbrain reticular formation had characteristic morphologies and laminar distributions within the tectum. However, these afferents fall into two groups based on their spatial organization. Afferents from the thalamus and nucleus isthmi arise from small neurons with spatially restricted, highly branched dendritic trees. Their axons terminate in single, highly branched and bouton‐rich arbors about 100 μm in diameter. By contrast, afferents from the midbrain reticular formation and the pretectum arise from large neurons with long, radiate, and sparsely branched dendritic trees. Their axons course parallel to the tectal surface and emit numerous collateral branches that are distributed widely through the mediolateral and rostrocaudal extent of either the central or superficial gray layers. Each collateral bears several small, spatially disjunct clusters of boutons.
Stimulation‐induced [14C]2‐deoxyglucose labeling of synaptic activity in the central auditory system
Authors: Nudo R. J. , Masterton R. B.
Published: January 2005

The relative contribution of active synapses and discharging neurons to [14C]2‐DG labeling in film autoradiographss of the auditory system was studied in a series of three experiments, two in cat, one in chick. In the first, the lateral superior olive in cats was specially prepared so that its inhibitory afferents could be stimulated without concurrent stimulation of its excitatory afferents. The film autoradiographs showed clear 2‐DG labeling in the vicinity of the activated inhibitory synapses.

In the second experiment, the medial superior olive in cat was specially prepared so that it could be stimulated antidromically without concurrent orthodromic stimulation. The film autoradiographs showed little or no elevations in 2‐DG labeling of the antidromically stimulated nucleus over its unstimulated contralateral control despite heavy labeling of nearby orthodromically stimulated nuclei.

In the third experiment, the highly polarized nucleus laminaris of a chick was specially prepared so that one set of its excitatory afferents could be stimulated without concurrent stimulation of the other set. The film autoradiographs showed that the distribution of heavy 2‐DG labeling matched the distribution of the activated synapses and not the distribution of discharging postsynaptic membrane.

The outcomes of the three experiments taken together suggest that it is active synapses and not actively discharging neurons that dominate typical [14C]2‐DG film autoradiographs, at least of the vertebrate central auditory system. It follows that [14C]2‐DG labeling of central auditory system tissue is not necessarily evidence of local cell discharge but instead evidence of synaptic activity whether excitatory or inhibitory, and whether or not it is accompanied by significant levels of postsynaptic cell discharge.
Functional morphology of insect neuronal cell‐surface/glial contacts: The trophospongium
Authors: Hoyle Graham , Williams Melissa , Phillips Christine
Published: January 2005

Ultrastructural studies were carried out on the surfaces of insect nerve cell bodies. Some of the neurons were identified, by using physiological criteria, before filling with dye. Their surface patterns were compared, to provide data needed for understanding dynamic relationships with glial cells, in the trophospongium. The data are also needed in connection with interpretation of electrical signals recorded from the somata and of their roles in integration and in learning and memory. The surfaces were found to be extremely complex and also varied, even for neurons of comparable size and function, as well as for different regions of the same neuron, suggesting that the surface is constantly changing as the neuron receives food and loses waste. There is a variety of cytoplasmic types of invagination of neuron somata by glial processes. The invaginations were classified into four easily recognized types: regular, chunky, filigree, and ridge (present only in axon hillock regions). Motor neurons also make reciprocal invaginations into the glial cells that surround them. Some of these extend for distances up to 40 μxsm from the surface. The effective surface area is increased, compared with that calculated for a smooth surface, as a result of the invaginations, by from as little as 5% for a small interneuron to as much as 12‐fold for a large motor neuron. The axon hillock region of all types of neurons is heavily invaginated.
Quantitative autoradiographic analysis of Mu and delta opioid binding sites in the rat hippocampal formation
Authors: Crain Barbara J. , Chang Kwen‐Jen , McNamara James O.
Published: January 2005

The distributions of mu and delta opioid binding sites were studied in rat hippocampal formation by using quantitative in vitro autoradiography. Mu binding sites, labeled with 125I‐FK‐33824, showed a highly organized laminar distribution. Binding was greatest at the foot of the obliterated hippocampal fissure in stratum lacunosum‐moleculare of CA3. Stratum pyramidale and stratum lacunosum‐moleculare of CA2 and stratum pyramidale of CA3 were next highest in mu binding, followed by stratum oriens and stratum radiatum of CA2, stratum oriens of CA3, and stratum pyramidale of CA1. The distribution of delta binding sites, labeled with 125.I‐D‐ala2 ‐Dleu5‐enkephalin in the presence of the unlabeled mu receptor ligand PL‐032, was similar to the distribution of mu binding in that binding within each region was greatest in a band centered over stratum pyramidale and in stratum lacunosum‐moleculare. Over all, delta binding was greatest in CA2 followed by CA3 and then CA1. Compared to mu binding, delta binding was relatively enriched in stratum moleculare of the dentate gyrus. These laminar distributions correlate reasonably well with the distribution of enkephalin immuno‐reactivity in hippocampal formation, although binding was surprisingly low in stratum lucidum, an area rich in dynorphin and enkephalin immunoreactivity.
Postnatal development of serotonin nerve fibers in the somatosensory cortex of mice studied by immunohistochemistry
Authors: Fujimiya Mineko , Kimura Hiroshi , Maeda Toshihiro
Published: January 2005

Postnatal serotonin (5HT) innervation in the cerebral cortex of mice has been studied by 5HT immunohistochemistry. 5HT‐like immunoreactive (5HT‐LI) nerve fibers and terminals appeared to increase transiently, particularly in the somatosensory (Sm) cortex during early postnatal days. As pups grow, 5HT afferent inputs decreased rapidly to reach a similar pattern of distribution to that in adult animals. Since the transient increase was seen at a critical period (seventh postnatal day) for the differentiation of layer IV, it is suggested that increased 5HT concentrations might have an effect on thalamocortical inputs and/or cortical lamination of the developing brains.
Retinotopic organization within the cat's posterior suprasylvian sulcus and gyrus
Authors: Updyke B. V.
Published: January 2005

The organization of extrastriate visual areas of the cat's posterior suprasylvian sulcus and gyrus was studied with electrophysiological mapping methods. Analysis of retinotopic organization confirmed the presence of dorsal lateral and ventral lateral suprasylvian (DLS, VLS) visual areas (Palmer et al., '78, J. Comp. Neurol. 177:237‐256) and demonstrated new features of organization. Areas DLS and VLS occupy the upper two‐thirds of the posterior suprasylvian sulcus, with DLS wholly confined to the upper bank and VLS straddling the sulcal fundus. Both areas contain a partial representation of the lower quadrant of the visual field. A narrow strip of visually responsive cortex (periauditory belt) was identified adjoining DLS on the posterior ectosylvian gyrus; its organization and extent were not explored in detail.

The organization of the posterior suprasylvian areas (PS) (Updyke, '82, Soc Neurosci. Abst. 8:810) was explored in detail. Area PS lies inferior to areas VLS and 21b in the lower third of the posterior suprasylvian sulcus and gyrus, extending onto the fusiform gyrus. PS contains a partial representation of the lower quadrant of the visual field. It shares a representation of horizontal meridian with area 21b and a representation of central gaze with area VLS. Analysis of the PS/20 border region indicates that the representation of the lower quadrant periphery is common to the borders of PS, 20a, and 20b rather than lying internal to areas 20a and 20b as suggested by Tusa and Palmer ('80, J. Comp. Neurol. 193:147‐164).
Projections from the parabigeminal nucleus to the dorsal lateral geniculate nucleus in the tree shrew Tupaia glis
Authors: Hashikawa T. , Van Lieshout D. , Harting J. K.
Published: January 2005

The parabigeminal nucleus receives its major input from the superficial layers of the superior colliculus via the tectoparabigeminal projection. An extensive reciprocal parabigeminotectal pathway has also been observed. This close connectional association between the superficial gray and the parabigeminal nucleus is reflected in the collicularlike response characteristics of parabigemiml neurons (see Sherk: Brain Res. 145:375‐379, '78, J. Neurophysiol 42:1640‐1655, 1656‐1668, '79a,b, for review).

Further documentation of the connectional relationship between the superior colliculus and the parabigeminal nucleus comes from the present data. Thus, our retrograde and anterograde transport findings reveal an extensive projection from the parabigeminal nucleus to layers 3 and 6 and several inter antinar zones of the contralateral dorsal lateral geniculate nucleus. These same layers and interlaminar zones receive tectogeniculate axons and have been shown to contain small cells that project to layers 1 and 3 of area 17.

In addition to the distribution of parabigeminal axons to tectally innervated, small‐celled zones, considerable parabigeminal input also reaches layers 1 and 5 of the tree shrew lateral geniculate nucleus. Each of these layers is the ipsilaterally (i.e., retinal) innervated component of a matched pair (layers 1 and 2 are considered magnocellular, while 4 and 5 are parvicellular), and it has been shown that layer 1 projects to lamina IVa of area 17, while layer 5 projects to lamina IVB. When the total distribution of parabigeminogeniculate axons is considered, it is apparent that the cells of origin of each of the major (small‐celled, parvi‐ and magnocellular) geniculocortical channels receives parabigeminal input. Such an extensive distribution of parabigeminal axons within the lateral geniculate nucleus suggests that the information they convey might play an, important role in geniculocortical function(s).
Neuronal architecture in the rat central nucleus of the amygdala: A cytological, hodological, and immunocytochemical study
Authors: Cassell M. D. , Gray T. S. , Kiss J. Z.
Published: January 2005

The organization of neurons in the rat central nucleus of the amygdala (CNA) has been examined by using Nissl stain and immunocytochemical and retrograde tracing techniques. Four main subdivisions were identified on the basis of quantitative analyses of Nissl‐stained material: medial (CM), lateral (CL), lateral capsular (CLC), and ventral (CV). An intermediate subdivision (CI), previously described by McDonald ('82), was apparent only in animals that had HRP‐WGA injected into the bed nucleus of the stria terminalis. Large populations of neurotensin‐, corticotropin‐releasing factor (CRF)‐, and enkephalin‐immunoreactive neurons were present within the lateral divisions (mainly CL), although they were also seen within CM. Somatostatin‐immunoreactive neurons were distributed mainly within CL and CM. Within CL, neurotensin and enkephalin‐immunoreactive neurons were more numerous laterally whereas CRF and somatostatin‐immunoreactive neurons were more numerous medially. Substance P‐immunoreactive neurons were almost exclusively confined to CM. Only a few cholecystokin‐and vasoactive‐polypeptide‐immunoreactive neurons were seen in the CNA, and they were observed within CL, CV, and CM. The majority of neurons projecting to the dorsal medulla, hypothalamus, and ventral tegmental area were located within CM, although a significant number of cells were also seen within CL. Efferent projections to the bed nucleus of the stria terminalis were found to arise from neurons located within all subdivisions of the CNA. Thus, the distributional patterns of peptidergic and efferent neurons were not confined to individual cytoarchitectonically defined subdivisions of the CNA. Rather, the results suggest overlapping medial to the lateral trends. Comparisons with the results of previous studies indicate that peptidergic and afferent terminal distribution patterns are more restricted to individual cytoarchitectonically defined subregions of the CNA. These observations suggest that the detailed cytoarchitecture of the CNA more likely reflects the functional integration of afferents rather than the organization of the CNA output neurons.
Intraspinal transplantation of embyronic spinal cord tissue in neonatal and adult rats
Authors: Reier P. J. , Bregman B. S. , Wujek J. R.
Published: January 2005

Fetal rat spinal cord tissue was obtained on gestational day 14 (E14) and transplanted into 2–4‐mm‐long intraspinal cavities produced by partial spinal cord lesions in adult and neonatal rats. At regular post‐transplantation intervals, light and electron microscopy, autoradiographic demonstration of tritiated thymidine labelling, and immunocytochemical localization of glial fibrillary acidic protein (GFAP) were used to identify surviving donor tissues and to study their differentiation and extent of fusion with recipient spinal cords. In some experiments, wheat germ agglutinin‐conjugated horseradish peroxidase (WGA‐HRP) was also employed to examine whether neurons within the grafts projected axons into the host spinal cord and vice versa. Lastly, immunocytochemistry was used to determine whether any supraspinal serotoninergic (5‐HT) axons from the host extended into the transplants.

Over 80% of the grafts survived in lesions of both the neonatal and adult rat spinal cord for periods of 1–16 months (duration of experiment), and considerable maturation of donor tissue was evidenced, which even included the appearance of some topographical features of the normal spinal cord. Many of the transplants extended the entire length of the lesion, and were often closely apposed to the injured surfaces of the recipient spinal cords without an intervening dense glial scar. At post‐transplantation intervals of 2–4 months, injection of WGA‐HRP into the host spinal cord (5 mm from the transplant in adult animals or as much as 20 mm in neonatal recipients) demonstrated retrogradely labelled neurons and anterogradely labelled axons in the grafts. Likewise, injecting WGA‐HRP into transplants in adult recipients resulted in labelling of neurons in adjacent segments of the host spinal cord; some labelled axons, derived from donor neurons, were also present in neighboring spinal gray matter. Finally, immunocytochemistry revealed 5‐HT‐like immunoreactive fibers in transplants that had been prelabelled with tritiated thymidine. These observations demonstrate the potential of embryonic spinal cord transplants to replace damaged intraspinal neuronal populations and to restore some degree of anatomical continuity between the isolated rostral and caudal stumps of the injured mammalian spinal cord.