bluuebunny/crossref_metadata_2025 huggingface dataset:
Collaterals of primate spinothalamic tract neurons to the periaqueductal gray
Authors: Zhang Dongxian , Carlton Susan M. , Sorkin Linda S. , Willis William D.
Published: January 2005

Collateral projections are an important feature of the organization of ascending projections from the spinal cord to the brain. Primate spinothalamic tract (STT) neurons with collaterals to the periaqueductal gray (PAG) were studied by means of a fluorescent double‐labeling method. Granular Blue and rhodamine‐labeled latex microspheres were placed in the ventral posterior lateral (VPL) nucleus of the thalamus and the periaqueductal gray, respectively. Single and double labeled neurons were studied in the upper cervical cord, cervical enlargement, thoracic cord, lumbar enlargement, and sacral segments.

The laminar distribution of double labeled neurons was similar to that of spinomesencephalic tract (SMT) neurons. Most double labeled (STT‐SMT) neurons were located in contralateral laminae I, V, VII, and X. Relatively more lamina I STT‐SMT neurons were found in the cervical enlargement and more lamina V STT‐SMT neurons in the lumbar enlargement. The density of STT‐SMT neurons in the upper cervical segments and cervical enlargement was almost equal. The density of STT‐SMT neurons in the lumbar enlargement was 40% of that in the cervical enlargement. The thoracic and sacral segments had the lowest density of STT‐SMT neurons, about 10% of that in the cervical enlargement. STT‐SMT neurons constituted 14.7% of SMT neurons and 6% of STT neurons in the cervical enlargement and 15.3% of SMT neurons and 2.9% of STT neurons in the lumbar enlargement.

The branch points of eight STT‐SMT axons were studied electrophysiologically. The average percentage of conduction time spent in the parent axon was more than 85% for an antidromic action potential from the VPL nucleus and 91% from the PAG. Branch points of STT‐SMT axons were calculated to be 9–13 mm caudal to the PAG, in the pons or rostral medulla.
Cholecystokinin and neurotensin mRNAs are differentially expressed in subnuclei of the ventral tegmental area
Authors: Jayaraman A. , Nishimori T. , Dobner P. , Uhl G. R.
Published: January 2005

Immunohistochemical studies of ventral tegmental area (VTA) neurons indicate that individual cells can contain dopamine as well as the neuropeptide neurotransmitters cholecystokinin (CCK) and neurotensin (NT). We have defined the distribution of the cells expressing the mRNAs encoding these two dopamine cotransmitter peptides in each of the subnuclei of the ventral tegmental area, and quantitated the extent of expression of each gene by using in situ hybridization methods.

These studies reveal significant differences in the patterns of expression of each of these two genes within various subdivisions of the VTA. The rostral linear nucleus contained numerous CCK positive cells, some of which appeared to express preproCCK‐mRNA at a very high level, but this nucleus contained relatively few NT‐expressing cells. The parabrachialis pigmentosus contained numerous NT and CCK positive cells. The paranigralis and interfascicularis nuclei displayed positive CCK cells but with expression at only modest levels. NT cells were very few in these nuclei. The caudal linear nuclei contained the highest number of NT‐expressing neurons and these cells expressed very high levels of NT mRNA.

The selective distribution of these peptide genes within the VTA subnuclei may have specific consequences. Studies of the connectivity of neurons in the VTA show that the different subnuclei of this region project to several functionally and architectonically different regions of the cerebral cortex and subcortically to nuclei related to the limbic system. Results from our study show very prominent expression of CCK mRNAs in those subnuclei that project heavily to the prefrontal, other cortical areas, and the amygdaloid complex. The NT gene is expressed prominently in those subnuclei of VTA that project heavily to the entorhinal cortex and amygdaloid complex.

These results provide support for a differential role for the NT‐expressing neurons than that of CCK‐expressing neurons of VTA in “reward” mechanisms and in drug‐seeking and motivational behavior. These observations could be applied to create working hypotheses and experimental paradigms to test the differential functional activity of the subdivisions of VTA and their potential roles in the pathogenesis and treatment of drug‐seeking behavior and other neuropsychiatric disorders.
Horseradish peroxidase labeling of the efferent and afferent pathways of the avian tangential vestibular nucleus
Authors: Cox Robert G. , Peusner Kenna D.
Published: January 2005

The efferent and afferent pathways of the chick tangential nucleus were studied by using horseradish peroxidase (HRP: Sigma type VI) to label nerve cell bodies and fibers. Depositions of HRP into the tangential nucleus, as well as into the second cervical level of the spinal cord, show that the axons of tangential neurons on leaving the nucleus form an anteriorly coursing tract that passes through the ventrolateral vestibular nucleus without branching and then to the contralateral medial longitudinal fasciculus (MLF). Within the MLF, the tangential axons course posteriorly, forming collaterals that innervate the abducens nucleus, and then proceed to the cervical spinal cord. This pathway was demonstrated for the axons of the two main neurons, the principal and elongate cells, in 1‐day, 1‐week, and 7‐week‐old animals. In addition, we propose the existence of an unidentified, ipsilateral pathway to the spinal cord for the tangential axons, since HRP injections into one side of the spinal cord resulted in the bilateral labeling of tangential neurons. No labeled cells were found in the tangential nucleus following HRP depositions into the uvula, flocculus, pontine reticular formation, nucleus piriformis, nucleus jumeaux, vestibulocerebellar nucleus, retrotangential nucleus, or the dorsomedial part of the medial vestibular nucleus.

The tangential nucleus receives afferents from the colossal vestibular fibers (spoon endings), small collaterals of fine vestibular ampullary fibers, flocculus, and high cervical levels of the spinal cord. From our small sample, it appears that the spinal cord fibers form most of the afferent terminals in the tangential nucleus in 1‐day, 1‐week, and 7‐week‐old animals.
Descending pathways to the spinal cord, III: Sites of origin of the corticospinal tract
Authors: Nudo R. J. , Masterton R. B.
Published: January 2005

The somata of corticospinal neurons were labeled with horseradish peroxidase that had been applied to a hemisection of the spinal cord at the C1‐C2 junction in 22 species of mammals. After tetramethylbenzidine processing, with and without counterstaining with cresyl violet or neutral red, the labeled cells in systematic sets of sections throughout the cerebral cortex were plotted and counted. Several morphological features of the corticospinal cells were examined including their cell type, number, density, concentration, laminar distribution, and their distribution across the cortical surface.

The results show that the labeled corticospinal neurons were invariably layer V pyramidal cells. However, in many mammals they were found to be stacked one above the other within layer V, sometimes many neurons deep. Despite the concentration of corticospinal neurons within layer V, many unlabeled neurons were also present within the layer throughout the extent of the labeled region.

The results also indicate that at least two spatially distinct regions of neocortex originate corticospinal fibers in each of the animals in the sample. In addition to these two regions, a third segregated region is present in the cortex of primates and an apparently different third region is present in the cortex of Glires ((Rodentia and Lagomorpha)). The third region of corticospinal cortex in primates is located on the lateral surface of the cortex in prosimians and New World monkeys and is buried in the caudal bank of the inferior arcuate sulcus in Old World monkeys.

The results also show a predominantly contralateral corticospinal tract in all but 4 of the 22 mammals in the sample. Although these 4 mammals are each members of the order Insectivora, a less modified member of the same order possessed the predominantly contralateral projection of most mammals, hence denying the notion that a predominantly ipsilateral tract is a characteristic of Insectivora.
Descending pathways to the spinal cord, IV: Some factors related to the amount of cortex devoted to the corticospinal tract
Authors: Nudo R. J. , Masterton R. B.
Published: January 2005

In the companion paper to this one ((Nudo and Masterton: J. Comp. Neurol. 296:559–583. '90)), we have presented data indicating that in each of 22 mammals, there are either 2 or 3 separate regions of neocortex contributing corticospinal fibers. In this paper, we describe the variation in the absolute size of these cortical regions, the total amount of neocortex contributing corticospinal fibers ((CST cortex)), and the total amount of neocortex ((total cortex)) in each of the animals. We then use strict statistical tests to examine the relationships between these measures and several other quantitative measures or descriptions of the animals' size, ancestral heritage, motor prowess, and ecological adaptation.

The results show that the absolute amout of CST cortex is more closely related to the total amount of neocortex than to any other quantitative measure available. The further variation—that is, the variation in the amount of CST cortex relative to total neocortex—appears to have been random over the inferred ancestral lineages of most animals in the sample, but seems to have been almost absent along the anthropoid lineage. Because this constancy in the relative amount of CST cortex over a very long period of anthropoid ancestry is apparently unusual if not unique among mammals, it may contain a clue to the special role of the corticospinal tract among primates.

Finally, the distribution of the CST among the 3 cortical regions in primates was found to be more closely related to their particular mode of ecological adaptation than to their particular combination of digital dexterity and hand‐eye coordination.
Burst generating and regular spiking layer 5 pyramidal neurons of rat neocortex have different morphological features
Authors: Chagnac‐Amitai Yael , Luhmann Heiko J. , Prince David A.
Published: January 2005

Intracellular recordings were obtained from pyramidal neurons in layer 5 of rat somatosensory and visual cortical slices maintained in vitro. When directly depolarized, one subclass of pyramidal neurons had the capacity to generate intrinsic burst discharges and another generated regular trains of single spikes. Burst responses were triggered in an all‐or‐none manner from depolarizing afterpotentials in most bursting neurons. Regular spiking cells responded to electrical stimulation of ascending afferents with a typical EPSP‐IPSP sequence, whereas IPSPs were hard to detect in bursting cells. Orthodromic activation of the latter evoked a prominent voltage‐dependent depolarization that could trigger a burst response. Intracellularly labelled bursting and regular spiking cells were located in layer 5b, but had distinctly different morphologies. Bursting neurons had a large pyramidal soma, a gradually emerging apical dendrite, and an extensile apical and basal dendritic tree. Their axonal collateral arborization was predominantly limited to layers 5/6. In contrast, regular spiking cells had a more rounded soma with abruptly emerging apical dendrite, a smaller dendritic arborization, and 2 to 8 ascending axonal collaterals that arborized widely in the supragranular layers. Both bursting and regular spiking cells had main axons that entered the subcortical white matter.

These data show that some subgroups of pyramidal neurons within the deeper parts of layer 5 of rat cortex are morphologically and physiologically distinct and have different intracortical connections. Bursting cells presumably function to amplify and synchronize cortical outputs, whereas regular spiking output neurons provide excitatory feedback to neurons at all cortical levels and receive a more effective orthodromic inhibitory input. These data support the hypothesis that differences in gross neuronal structure, perhaps even the subtle differences that distinguish subclasses of neurons in a given lamina, are predictive of underlying differences in the type and distribution of ion channels in the nerve cell membrane and connections of cells within the cortical circuit.
Cutaneus trunci muscle reflex of the guinea pig
Authors: Blight Andrew R. , McGinnis Michael E. , Borgens Richard B.
Published: January 2005

The cutaneus trunci muscle reflex in guinea pigs was studied with a combination of video analysis, electromyography, lesioning, and light microscopy. The muscle forms a bilateral, subdermal sheet over much of the trunk. Local contractions of the dorsal part of the muscle are produced in response to brief tactile or electrical stimulation of the skin and consist of a twitch centered 1–2 cm rostral of the stimulus site. The reflex receptive field covers most of the thoracic and lumbar dorsal surface. The sensory information is carried via segmental dorsal cutaneous nerves. Receptive fields of adjacent nerves overlap and form rectangular areas perpendicular to the midline, at thoracic levels. Motor innervation projects through the lateral thoracic nerves of the brachial plexus. The motoneurons are located near the cervical thoracic junction ((C7‐T1)). Lesions of the lower thoracic cord indicate that ascending sensory information is carried to the motor nuclei via the ventral half of the lateral funiculus. This pathway conveys information primarily from ipsilateral skin. There is a weaker input from contralateral skin, crossing at segmental levels. Electromyographic responses to brief electrical stimulation of lower thoracic skin occur usually as 10–12 msec bursts at latencies of 10–20 msec, and do not readily habituate or fatigue at stimulus frequencies below 10 Hz. The reflex persists under light pentobarbital anesthesia. This combination of characteristics makes the reflex useful for a variety of physiological and pathophysiological studies.
Cholinergic manipulation alters stimulus‐evoked metabolic activity in cat somatosensory cortex
Authors: Juliano Sharon L. , Ma Wu , Bear Mark F. , Eslin Don
Published: January 2005

The role of acetylcholine (ACh) in cerebral cortical activity has recently been reevaluated. It now seems clear that this neurotransmitter increases the magnitude of cortical responses. Although substantial information has been gathered regarding the role of ACh in sensory information processing, little is known about the participation of ACh in the organization of maps in the cerebral cortex. To address this issue, we used 2 methods to manipulate the supply of ACh in the somatosensory cortex of cats: (1) unilateral neurotoxic lesions of the basal forebrain and (2) unilateral topical applications of the cholinergic antagonist, atropine. For each experimental condition, the animal received an injection of 2‐deoxyglucose (2DG) while identical somatic stimuli were delivered to the right and left forepaws. In the somatosensory cortex, the 2DG uptake most often occurred in the form of patches that extended from layer II to IV. When the patches were reconstructed into 2‐dimensional maps of activity throughout the somatosensory cortex, they formed strips that ran in the rostrocaudal direction. The reconstructed maps revealed that the 2DG patterns in ACh‐depleted and the normal cortex were similar in their overall topographic distribution. Depletion or antagonism of ACh, however, caused the stimulus‐evoked metabolic label to be reduced in dimension and density. Measurements of background activity levels were obtained by using (1) cytochrome oxidase histochemistry or (2) metabolic activity values in regions of somatosensory cortex that were not specifically stimulated. This analysis indicated that background values in the ACh‐depleted hemispheres were not different from those in the normal hemispheres. The absence of ACh therefore appears to reduce the cortical response to stimulation, while background activity values do not change. These observations indicate that ACh plays a significant role in the processing of sensory information and the organization of somatosensory cortical maps.
Distribution of two morphologically distinct subsets of serotoninergic axons in the cerebral cortex of the marmoset
Authors: Hornung Jean‐Pierre , Fritschy Jean‐Marc , Törk Istvan
Published: January 2005

The serotoninergic innervation of the marmoset (New World monkey, Callithrix jacchus) cerebral cortex has been analyzed by using immunocytochemistry. The use of a sensitive monoclonal antibody against serotonin allowed the visualization of the fine morphology of individual axons. Two types of terminal axons were demonstrated: one has sparse, small, ovoid varicosities (dia. less than 1 μm), and the other has large, spheroidal varicosities (up to 5 μm in dia.), which are more densely clustered. The first type of axon is distributed through all cortical layers, with a characteristic laminar distribution that varies from area to area. The second type of axons was distributed sparsely in all regions but was markedly denser in the frontal and anterior parietal lobes, and in the hippocampal formation.

Axons with large varicosities typically surrounded certain cell bodies and proximal dendrites, forming pericellular arrays, or baskets. These morphological specializations were most frequent in the frontal and anterior parietal cortex, where they were found around stellate and horizontal cells in layer I and around stellate and bipolar cells in layer II and III. Similar baskets were also found in the hippocampal formation, mainly along the border between the hilus and the granule cell layer of the dentate gyrus, across the CA4 field, and at each side of the pyramidal cell layer of the CA3 regions. The distribution and cellular morphology of the cell surrounded by the 5‐HT basket fibres were suggestive of a subpopulation of interneurons, possibly GABAergic and/or peptidergic. In agreement with previous reports on the innervation of the cerebral cortex of other mammalian species, the marmoset cerebral cortex is innervated by two separate subsystems of serotoninergic axons. One of these may have a strong and specific influence on the cortical inhibitory circuitry, via relay through cortical interneurons.
Organization of the spinal cord in four species of elasmobranch fish: Cytoarchitecture and distribution of serotonin and selected neuropeptides
Authors: Cameron Adrian A. , Plenderleith Mark B. , Snow Peter J.
Published: January 2005

An analysis of Nissl stained sections of the spinal cord taken from four species of elasmobranch showed that seven distinct cytoarchitectonic laminae are present. These laminae are compared with laminae described previously in the spinal cord of other vertebrates.

The distribution of immunoreactivity to serotonin, substance P, somatostatin, calcitonin gene‐related peptide, neuropeptide Y, and bombesin was determined in the brown stingray (Dasyatis fluviorum), the eagle ray (Aetobatis narinari), the shovelnose ray (Rhinobatis battilum), and the black‐tip shark (Carcharhinus melanopterus). In all species, dense immunoreactivity to most substances tested was found in the outer part of the substantia gelatinosa. Many fibres and varicosities immunoreactive to substance P, calcitonin gene‐related peptide, and bombesin were found in this region and smaller numbers of fibres were found in the nucleus proprius. Immunoreactivity to somatostatin consisted of coarse fibre bundles that entered the dorsal horn at the nucleus proprius and radiated dorsally to the substantia gelatinosa. Axons and varicosities immunoreactive to serotonin and neuropeptide Y were found in all regions of the dorsal horn but were concentrated in the outer part of the substantia gelatinosa. The distribution of immunoreactivity to met‐enkephalin in the shovelnose ray was concentrated in the lateral third of the substantia gelatinosa and to a lesser extent in the nucleus proprius.

The distribution of these substances is compared with that described in other vertebrates. Although the sensory information reaching the elasmobranch spinal cord is limited, compared with that of mammalian species, the distribution of these neuroactive factors in the dorsal horn of the two groups is strikingly similar.
Distribution of motor neurons into anatomical groups in the grasshopper metathoracic ganglion
Authors: Siegler Melody V. S. , Pousman Cynthia A.
Published: January 2005

Motor neurons of the main muscles of the hind legs and the hind wings of the grasshopper are distributed into eight anatomical groups within each half of a bilaterally symmetrical segmental ganglion. A group contains 5 to 24 identified motor neurons, accounting for 164 (82 pairs) of the some 200 motor neurons within the population. The motor neurons within a given group may contribute axons to more than one of the lateral nerves, and conversely each lateral nerve contains axons arising from motor neurons in separate groups. Groups may include synergistic and antagonistic motor neurons as well as those that have unrelated functions. The motor neurons of a given muscle may occur together in a single group, or separately in two or more groups. The description of groups provides a way of classifying neurons to simplify and organize the large amount of data on the structure and function of individually identified neurons within the ganglion. The organization of the motor neurons into groups may reflect their developmental origin from individual neuroblasts, and the detailed information about the pattern of groups in the adult thus allows specific predictions to be made about the composition of neurons within neuronal lineages.
Effect of temperature on long‐term survival of anucleate giant axons in crayfish and goldfish
Authors: Blundon Jay A. , Sheller Rebecca A. , Moehlenbruck Jeffrey W. , Bittner George D.
Published: January 2005

The effect of temperature on the electrophysiology and morphology of anucleate axons was examined following severance of crayfish medial giant axons and goldfish Mauthner axons from their respective cell bodies. Although anucleate segments of each giant axon exhibited long‐term survival for weeks to months at 5–25°C in crayfish and 10–30°C in goldfish, the two axons differed in their survival characteristics. All measures of long‐term survival in crayfish medial giant axons were independent of animal holding temperature, whereas all measures in Mauthner axons were dependent on holding temperature. Medial giant axons survived for at least 90 days in crayfish maintained at 5–25°C in this and previous studies. Mauthner axons survived for over 5 months in goldfish maintained at 10°C but survived for 1 month at 30°C. Postoperative time had different effects on many single measures of long‐term survival (axonal diameter, amplitude of action or resting potentials) in medial giant axons compared to Mauthner axons. For example, resting and action potentials in crayfish medial giant axons remained remarkably constant at all holding temperatures for 0–90 postoperative days. In contrast, resting and action potentials in goldfish Mauthner axons declined abruptly in the first 10–20 postoperative days followed by a slower decline at each holding temperature. We suggest that the mechanism of long‐term survival is not necessarily the same in all anucleate axons.
Proctolin in the innervation of the locust mandibular closer muscle modulates contractions through the elevation of inositol trisphosphate
Authors: Baines Richard A. , Lange Angela B. , Downer Roger G. H.
Published: January 2005

Extracts of the locust (Locusta migratoria) mandibular closer muscle separated on reverse‐phase HPLC and tested for bio‐activity on the locust oviduct contain a bio‐active substance that coelutes with authentic proctolin. Furthermore, the effect on oviduct contractions of this compound is indistinguishable from that of authentic proctolin. Antiserum to proctolin stains numerous axons with beaded endings that run along the fibres of the closer muscles and, in addition, the antiserum stains a number of cell bodies in the suboesophageal ganglion, some of which have axons in the mandibular nerve that innervates the mandibular musculature.

The function of proctolin appears to be modulatory as its presence significantly increases the amplitude of neurally evoked contractions of the closer muscle. This effect can be mimicked by the addition of inositol 1,4,5,‐trisphosphate (IP3) to preparations in which the muscles have been permeabilized with dimethyl sulfoxide. The involvement of this second messenger is further implicated as we also show that proctolin produces a large, significant increase in the IP3 content of homogenized muscle.
Primary afferent origin of substance P‐containing axons in the superficial dorsal horn of the rat spinal cord: Depletion, regeneration and replenishment of presumed nociceptive central terminals
Authors: Knyihár‐Csillik Elizabeth , Török Ágotha , Csillik Bert
Published: January 2005

Substance P‐like immunoreactivity (SPLI) was localized in the superficial spinal dorsal horn of the rat by means of light and electron microscopic immunocytochemical techniques. Serial immunocytochemical sections were subjected to densitometric measurements with an electronic Image Analyser, and with aid of a computer program, a two‐dimensional reconstruction of the fine neuroanatomical structure of the SPLI‐active regions of the lumbosacral upper superficial spinal dorsal horn was obtained. SPLI activity in the superficial dorsal horn outlines four well‐marked and distinctly differing regions, called, in the mediolateral sequence, areas A, B, C, and D, plus Cajal's noyeau interstitiel (“lateral spinal nucleus” = “nucleus of the dorsolateral fascicle,” L). Lumbosacral dorsal rhizotomy results in an almost complete depletion of SPLI from ipsilateral areas A, B, C, and D; it induces decreased SPLI in the area of the lateral spinal nucleus (L), ipsi‐ or contralaterally in an alternating fashion. Transection of the segmentally related, ipsilateral peripheral nerve induces a marked depletion of SPLI from areas A, B, and C but only a slight decrease in area D and virtually none in the area of L. Whereas a simple crush of the peripheral nerve (axocompression) induces only a slight depletion of SPLI, if any, semiautomatic densitometric analysis of serial immunocytochemical sections proves that a controlled crush injury (axocontusion) results in depletion of SPLI from the upper dorsal horn, similar to transection of the peripheral nerve. Following regeneration of the ipsilateral, segmentally related peripheral nerve, the original immunocytochemical structure of the superficial dorsal horn is re‐established by SPLI‐positive axonal sprouts originating from previously damaged dorsal root axons.
Comparative study of histamine immunoreactivity in nervous systems of Aplysia and Pleurobranchaea
Authors: Soinila Seppo , Mpitsos George J. , Panula Pertti
Published: January 2005

The distribution of histamine in the nervous system of the marine molluscs Aplysia californica and Pleurobranchaea californica was studied by using a newly available immunohistochemical localization technique and specific antiserum against histamine‐protein conjugate. We examined several sets of complete histological sections through the major ganglia of both animals, as well as all nerve roots of the buccal and cerebral ganglia and the corresponding target tissues. The results indicate that histamine is present in several neurons and/or nerve fibers of all major ganglia. An especially dense histamine fiber network in the buccal ganglion of both species suggests a major role for histamine in regulation of buccal‐oral behaviors. Histamine was also observed in several identified nerve roots of the buccal and cerebral ganglia, as well as in the corresponding target tissues. Its localization in the Aplysia radular sac and in the statocyst neurons of both species suggest a role for histamine in sensory functions. Our study revealed many previously unknown histamine cells or cell clusters, some of which may be identifiable by electrophysiological methods. The findings also point to possible reinterpretation of previous findings, indicating that histamine may be a cotransmitter in identified cells, whereas the methodology itself suggests that special precautions must be taken to avoid spurious interpretations of specificity. As has now been observed in studies of serotonergic immunohistochemistry and in our own findings on VIP, histamine terminals were observed to lie in close contact with somata and axon hillocks, all of which suggest that axo‐somatic connections in molluscs may be more prevalent than previously considered.
Peripheral and central terminations of hypoglossal afferents innervating lingual tactile mechanoreceptor complexes in Fringillidae
Authors: Wild J. Martin
Published: January 2005

Injections of cholera toxin B subunit conjugated to horseradish peroxidase (CTB‐HRP) were made into the lingual branch of the hypoglossal nerve in four species of finch in order to identify the innervation of the mechanoreceptors of the dermal papillae of the tongue, and simultaneously to determine the pattern of central projections of lingual hypoglossal afferents. The results showed that hypoglossal fibers innervate all the Herbst corpuscles and terminal cell receptors of the elaborately organized papillae of the dorsum of the tongue, of the shorter papillae in the ventral tongue, and the loose collection of Herbst corpuscles in the subpapillary region. Labelled fibers were also observed in the intralingual glands, in the intrinsic tongue muscles, and in the posterodorsal epithelium where they formed budlike structures.

Retrogradely labelled cell bodies were located in the jugular ganglion and their central processes ascended and descended throughout the brainstem within the descending trigeminal tract (TTD). Terminal fields were observed within the dorsolateral part of the nucleus caudalis of TTD, predominantly ipsilaterally, and within the medial part of the dorsal horn of the first 4–6 cervical segments bilaterally. There were dense patches of termination over a dorsolateral subnucleus of the interpolated nucleus of TTD, and within two regions of the principal sensory trigeminal nucleus: a large one laterally and a small one medially.

Terminal fields were also observed within the nucleus ventralis lateralis anterior of the rostral solitary complex, and within adjacent nuclei, which are probably equivalent to the dorsal sensory nuclei of the facial and glossopharyngeal nerves of other avian species.

The results are interpreted in the light of the role of the tongue in species‐specific patterns of feeding in finches, and the possible requirement for the central integration of touch and taste.
Fine structure of the lateral mammillary projection to the dorsal tegmental nucleus of gudden in the rat
Authors: Hayakawa Tetsu , Zyo Katuya
Published: January 2005

The synaptic organization of projections from the lateral mammillary neurons within the dorsal tegmental nucleus of Gudden is studied in the rat with the aid of anterograde transport of horseradish peroxidase conjugated with wheat germ agglutinin (WGA‐HRP) and visualized with tetramethylbenzidine. The dorsal tegmental nucleus consists of the pars ventralis (TDV) and the pars dorsalis (TDD). The normal neuropil of the dorsal tegmental nucleus contains three classes of axodendritic terminals, that is, terminals containing round, flat, and pleomorphic vesicles. They make up 44%, 5%, and 51%, respectively, of all axodendritic terminals in the TDV, and 62%, 1%, and 37% in the TDD.

Injection of WGA‐HRP into the lateral mammillary nucleus permits ultrastructural recognition of many anterograde labeled terminals within both the TDV and TDD. In the TDV, 81% of the labeled terminals contain round synaptic vesicles and make asymmetric synaptic contacts. A few of the labeled terminals contain pleomorphic vesicles and make symmetric synaptic contacts. More than 50% of the labeled terminals contact intermediate dendrites (1–2 μm diameter). In the TDD, almost all labeled terminals are small, contain round vesicles, and make asymmetric synaptic contacts. These terminals mainly contact intermediate as well as distal (less than 1 μm diameter) dendrites. There are only a few labeled terminals with pleomorphic vesicles and no terminals with flat vesicles. The termination pattern of the lateral mammillary neurons in the TDV is similar to that in the TDD. Anterograde labeled axon terminals often contact retrograde labeled dendrites in the TDV. No reciprocal connections are present in the TDD. These results suggest that the TDV and the TDD receive mainly excitatory and a few inhibitory inputs from the lateral mammillary nucleus. The TDV neurons also have direct reciprocal connections with the lateral mammillary neurons.
Immunohistochemical study of the serotoninergic innervation of the basal ganglia in the squirrel monkey
Authors: Lavoie Brigitte , Parent André
Published: January 2005

A specific antibody raised against 5‐hydroxytryptamine (5‐HT) conjugated to bovine serum albumin was used to study the serotoninergic innervation of the basal ganglia in the squirrel monkey (Saimiri sciureus). At midbrain level, numerous fine 5‐HT‐immunoreactive axons were seen to arise from the immunopositive neurons of the dorsal raphe nucleus and less abundantly from those of the nucleus centralis superior. The bulk of these axons formed a rather loosely arranged bundle that arched ventrorostrally through the central portion of the midbrain tegmentum and ascended toward the ventral tegmental area. Several fascicles detached themselves from this bundle to reach the substantia nigra where they arborized into a multitude of heterogeneously distributed 5‐HT terminals. The 5‐HT innervation was particularly dense in the pars reticulata but much less so in the pars compacta of the substantia nigra. More rostrally other 5‐HT fibers swept dorsolaterally and formed a remarkably dense network of varicose fibers within the subthalamic nucleus. A multitude of 5‐HT axons continued their ascending course within the lateral hypothalamic area, and many of them swept laterally to invade the lenticular nucleus. At pallidal levels, the 5‐HT axons arborized much less profusely in the external segment than in the internal segment, which contained numerous 5‐HT varicose fibers and terminals arranged in a typical bandlike pattern. At striatal levels, the 5‐HT terminals were particularly abundant in the ventral striatum, including the nucleus accumbens and deep layers of the olfactory tubercle. They also abounded in the ventrolateral region of the putamen and the ventromedial aspect of the caudate nucleus. Overall, the number of 5‐HT fibers and terminals decreased progressively along the rostrocaudal axis of the striatum and several large and elongated zones rather devoid of 5‐HT immunoreactivity were visualized, particularly in the caudate nucleus and the dorsal putamen. These zones of poor 5‐HT immunoreactivity were in register with similar areas devoid of tyrosine hydroxylase immunoreactivity as seen on contiguous sections. These findings reveal that all the core structures of the basal ganglia in primates receive a significant serotoninergic input, but that the densities and patterns of innervation vary markedly from one structure to the other.
Thalamic projections to sensorimotor cortex in the macaque monkey: Use of multiple retrograde fluorescent tracers
Authors: Darian‐Smith Corinna , Darian‐Smith Ian , Cheema Surindar S.
Published: January 2005

We used several fluorescent dyes (Fast Blue, Diamidino Yellow, Rhodamine Latex Microspheres, Evans Blue, and Fluoro‐Gold) in each of eight macaques, to examine the patterns of thalamic input to the sensorimotor cortex of macaques 12 months or older. Inputs to different zones of motor, premotor, and postarcuate cortex, supplementary motor area, and areas 3b/1 and 2/5 in the postcentral cortex, were examined. Coincident labeling of thalamocortical neuron populations with different dyes (1) increased the precision with which their soma distributions could be related within thalamic space, and (2) enabled the detection by double labeling, of individual thalamic neurons that were common to the thalamic soma distributions projecting to separate, dye‐injected cortical zones.

Double‐labeled thalamic neurons projecting to sensorimotor cortex were rarely seen in mature macaques, even when the injection sites were only 1–1.5 mm apart, implying that their terminal arborizations were quite restricted horizontally. By contrast, separate neuron populations in each thalamic nucleus with input to sensorimotor cortex projected to more than one cytoarchitecturally distinct cortical area. In ventral posterior lateral (oral) (VPLo), for example, separate populations of cells sent axons to precentral medial, and lateral area 4, medial premotor, and postarcuate cortex, as well as to supplementary motor area.

Extensive convergence of thalamic input even to the smallest zones of dye uptake in the cortex (≈0.5 mm3) characterized the sensorimotor cortex. The complex forms of these projection territories were explored using 3‐dimensional reconstructions from coronal maps. These projection territories, while highly ordered, were not contained by the cytoarchitectonic boundaries of individual thalamic nuclei. Their organization suggests that the integration of the diverse information from spinal cord, cerebellum, and basal ganglia that is needed in the execution of complex sensorimotor tasks begins in the thalamus.
Development and plasticity of the serotoninergic projection to the Hamster's superior colliculus
Authors: Rhoades Robert W. , Mooney Richard D. , Chiaia Nicolas L. , Bennett‐Clarke Carol A.
Published: January 2005

Immunocytochemical techniques were employed to investigate the normal adult organization, development, and effects of both neonatal and adult eye removal upon the organization of the serotoninergic projection to the hamster's superior colliculus. Immunocytochemistry, both alone and in combination with retrograde tracing with true blue and fluorogold, was used to determine the organization of the serotoninergic projection to the superior colliculus in normal adult hamsters. Immunoreactive fibers were present in all laminae of the superior colliculus, but they were most dense in the lower part of the stratum griseum superficiale, the stratum opticum, the stratum griseum profundum, and the stratum album profundum. When retrograde tracing from the colliculus was combined with immunocytochemistry for serotonin, cells containing both labels were found in the lateral portions of the nucleus raphe dorsalis and also in periaqueductal gray, the median and pontine raphe nuclei, and in the region of the medial lemniscus. Such cells were visible both ipsilateral and contralateral to the injection site.

Serotonin immunoreactive fibers were visible in the superior colliculus by embryonic day 14 (2 days prior to birth). On the day of birth, a small number of immunoreactive fibers were present just below the pial surface and others were generally oriented either parallel or orthogonal to the collicular laminae. At this age, there were also many immunoreactive fibers that crossed from one side of the brainstem to the other in the commissure of the superior colliculus. Some serotonin‐positive axons appeared to terminate as growth cones in fetal and newborn hamsters. Over the next 2 weeks, the serotoninergic innervation of the SC increased in density and assumed the laminar distribution observed in adult animals. By this age, only a very few immunoreactive fibers were present in the commissure of the superior colliculus.

Removal of one eye on either on the day of birth or in adulthood resulted in reorganization of the serotoninergic innervation of the partially deafferented colliculus. There was a marked increase in the density of serotonin‐positive fibers in the upper stratum griseum superficiale on the side ipsilateral to the remaining eye. This change was apparent within 2 weeks after enucleation in either neonatal or adult animals. Quantitative analysis demonstrated that the magnitude of this effect was greater after adult enucleation than after neonatal eye removal. Both neonatal and adult enucleation also resulted in an increase in the density of the serotoninergic projection to the dorsal and ventral lateral geniculate nuclei ipsilateral to the remaining eye.
Immunocytochemical localization of protein kinase C subspecies in the rat spinal cord: Light and electron microscopic study
Authors: Mori Miyako , Kose Akiko , Tsujino Takeshi , Tanaka Chikako
Published: January 2005

Distinct expression of protein kinase C (PKC) subspecies in the central nervous system suggested that each subspecies has a distinct neural function in the processing and modulation of a variety of physiological responses to external signals. In this study, the cellular and subcellular distributions of βI‐, βII‐ and γ‐subspecies of PKC were demonstrated by using subspecies‐specific antibodies in the rat spinal cord.

By light microscopy both γ‐ and βII‐subspecies immunoreactivities were found only in neurons of the substantial gelatinosa and axons of the dorsal corticospinal tract in the spinal cord. Use of a double staining method, however, revealed that βII‐subspecies immunoreactivity was localized in the outer part of the lamina II, whereas γ‐subspecies immunoreactivity was found in the inner part of lamina II. Immunoreactive neurons containing βI‐subspecies were scattered in the substantia gelatinosa. Beta I‐subspecies immunoreactivity varied in neuronal types. Furthermore, electron microscopic analysis clearly showed the subcellular distribution of these subspecies to be different from one another. Dense γ‐subspecies immunoreactivity was found in the cytoplasm except within cell organelles of the perikarya and dendrites. Some nuclei were stained as strongly as the cytoplasm and others were stained less heavily. The nucleoli had faint or no immunoreactivity. Reaction products of βII‐subspecies were located against the inner plasma membrane but not seen in the nuclei or nucleoli. Beta I‐subspecies immunoreactivity appeared to be associated with the Golgi complex. No immunoreactive products of any PKC subspecies were detected in the presynaptic terminals.

The different patterns of expression described above imply that individual PKC subspecies may have a specific function in modulating the neuronal activity in the different neurons of the spinal cord.
Single fiber studies of ascending input to the cuneate nucleus of cats: II. Postsynaptic afferents
Authors: Pierce Joseph P. , Weinberg Richard J. , Rustioni Aldo
Published: January 2005

The morphology of single postsynaptic afferent fibers terminating in the feline cuneate nucleus was investigated by using transport of Phaseolus vulgaris leucoagglutinin from the cervical spinal cord and intraaxonal injections of horseradish peroxidase into identified postsynaptic fibers in the cuneate fasciculus.

Injections of Phaseolus in C5 and C6 of both rhizotomized and non‐rhizotomized cats gave similar results and confirmed previous observations with other techniques. In one animal with the smallest injection and the fewest labeled fibers in the cuneate nucleus, ten individual collaterals were reconstructed from serial sections. Most of these collaterals were at middle levels of the cuneate (from obex to about 4 mm caudal to it); they were largely confined to the rim and ventral regions of the nucleus, and their terminal fields were restricted rostrocaudally. Electrophysiologically identified fibers stained with horseradish peroxidase had large receptive fields on the ipsilateral forepaw, and latencies suggesting an oligosynaptic link to the periphery. Most of the collaterals from these fibers were also at middle cuneate levels and terminated mainly at the periphery of the nucleus but gave rise to larger terminal arbors, including sparse terminal branches to the core of the nucleus.

Individual postsynaptic fibers differed in several respects from primary afferent fibers. While the spacing of collaterals of postsynaptic fibers was intermediate between that of G hair and Ia fibers, their arbors were larger than either, and could extend through the dorsoventral extent of the cuneate nucleus. The pattern of bifurcation of postsynaptic fibers resulted in stringier arbors which encompassed larger and less dense terminal fields than those of primary afferents. The number of boutons per collateral was intermediate between G hair and Ia fibers, but boutons of postsynaptic fibers were substantially smaller. These morphological differences are consistent with distinct functional roles for the two main ascending afferent systems, as suggested by electrophysiological data.
Proximity as a factor in the innervation of host brain regions by retinal transplants
Authors: Radel J. D. , Hankin M. H. , Lund R. D.
Published: January 2005

Embryonic mouse retinae transplanted to a variety of locations within the rostral midbrain of neonatal rats exhibit selective innervation of host visual nuclei when studied at maturity. Some of these nuclei (superior colliculus, nucleus of the optic tract, dorsal terminal nucleus) usually receive extensive transplant projections, others are innervated partially (dorsal division of the lateral geniculate nucleus, olivary pretectal nucleus, medial terminal nucleus), while a few (ventral division of the lateral geniculate nucleus, suprachiasmatic nucleus, intergeniculate leaflet) are not innervated at all. The selectivity of this innervation is largely independent of the transplant's position within the rostral brainstem, while the density of innervation of individual nuclei depends in part upon the proximity of the transplant to the nucleus and upon whether the host retinal projection to that nucleus is present or absent. These findings provide a foundation for further studies of the behavioral capabilities of retinal transplants, for developmental studies of factors responsible for the establishment of normal neural projections, and for examination of the immunological consequences of transplantation.
Monoclonal antibody cat‐301 identifies Y‐cells in the dorsal lateral geniculate nucleus of the cat
Authors: Hockfield Susan , Sur Mriganka
Published: January 2005

In mammalian visual pathways, information is carried in parallel channels from the retina through the visual thalamus to visual cortex. The cat's visual pathway comprises at least three major channels that begin with the X, Y, and W ganglion cells in the retina. In the dorsal lateral geniculate nucleus (LGN) of the thalamus, neurons in the X, Y, and W channels receive input from their retinal counterparts and can be discriminated from one another on the basis of their anatomical and physiological properties.

The search for molecular properties that might correlate with anatomically or physiologically defined classes of neuron has been a major area of research in recent years. Monoclonal antibody Cat‐301 recognizes a neuronal surface‐associated proteoglycan in many areas of the mammalian central nervous system. In the cat LGN Cat‐301 immunoreactivity is restricted to a subset of neurons. We show here that the distribution, size, morphology, and cortical projection pattern of Cat‐301‐positive LGN neurons match those previously described for Y‐cells. Taken together with our previous studies of the development of immunoreactivity and the sensitivity of Cat‐301 staining to visual deprivation, these studies suggest that Cat‐301 specifically recognizes Y‐cells in the cat‐LGN. These results indicate that neurons within a physiologically and anatomically denned cell class share a molecular property. They further suggest that differences in molecular traits may reflect, and possibly subserve, differences in anatomical and physiological characteristics.