bluuebunny/crossref_metadata_2025 huggingface dataset:
Three‐dimensional structure of astrocytes in the rat dentate gyrus
Authors: Kosaka Toshio , Hama Kiyoshi
Published: January 2005

Structural features of astrocytes in the rat dentate gyrus were studied by means of light and high‐voltage electron microscopy of Golgi‐impregnated materials, conventional electron microscopy, combined Golgi‐electron microscopy, and immunohistochemistry for glial fibrillar acidic protein.

Astrocytes in the dentate gyrus were of the protoplasmic type and were classified into six subtypes based on the location of their somata: i.e., astrocytes 1) in the polymorph layer, (2) in the subgranular zone, (3) in the granular cell layer, (4) at the border of the granular cell layer and the molecular layer, (5) in the molecular layer, and (6) subjacent to the pia surface.

Stereoscopic observations of 5‐μm‐thick sections of Golgi‐impregnated materials revealed three‐dimensional structural details of astroglial processes not apparent in either the light microscope or in conventional thinsection electron microscopy. Most of them were basically thin sheets, varying in shape and size in accordance with their sites. In the granule cell layer, thin veillike sheets or lamellae, originating from three kinds of astrocytes (subtypes 2, 3, and 4), intervened between granule cell somata, whereas in the plexiform and molecular layers small leafletlike appendages originating from astrocytes (subtypes 1, 2, 4, and 5) intermingled with one another, making spongelike conglomerates. Thus astrocytes in the subgranular zone and those at the border of the granule cell layer and the molecular layer showed prominent regional differentiation of their processes among layers. In addition to these sheetlike processes, thin threadlike processes were also common.
Anatomy and physiology of saccadic burst neurons in the alert squirrel monkey. I. Excitatory burst neurons
Authors: Strassman A. , Highstein S. M. , McCrea R. A.
Published: January 2005

Saccadic burst neurons in the pontine reticular formation have been implicated in the generation of saccades in the horizontal plane on the basis of lesion and extracellular recording studies in the cat and monkey. In the present study, saccadic burst neurons were anatomically and physiologically characterized with intraaxonal recording and injection of horseradish peroxidase in the alert squirrel monkey. A population of burst neurons were found that appear analogous to the excitatory burst neurons (EBNs) described previously in the cat. All neurons are located in the caudal pontine reticular formation and have a major axonal projection to the ipsilateral abducens nucleus. Additional projections were found to the medial vestibular nucleus, the nucleus prepositus, and regions of the pontine and medullar reticular formation rostral, ventral, and caudal to the abducens. All neurons fire exclusively during saccades and have a discharge pattern similar to that of medium‐lead burst neurons described previously in the cat and monkey. In most neurons the saccadic burst begins 5‐15 msec before saccade onset. Linear relationships exist between burst duration and saccade duration, number of spikes in the burst and saccade amplitude, and firing frequency and instantaneous velocity. Physiological activity of each neuron shows the closest relationship with the amplitude of the saccade component in a particular direction. For all neurons, this on‐direction is in the ipsilateral hemifield and is predominantly horizontal, but may have either an upward or downward vertical component. These results support a major role for the EBNs in the monkey in generating the saccadic burst in abducens motoneurons, as well as in contributing to the oculomotor activity in other classes of premotor neurons.
Functional heterogeneity in the myenter is plexus: Demonstration using cytochrome oxidase as a verified cytochemical probe of the activity of individual enteric neurons
Authors: Mawe Gary M. , Gershon Michael D.
Published: January 2005

The cytochemical technique for the demonstration of cytochrome oxidase has been used to locate the sites of chronically active neurons in the CNS. The current experiments were undertaken to validate the use of this technique for the identification of active neurons and ganglia in the myenteric plexus of the gut. The excitotoxin veratridine was used to cause repetitive firing of action potentials and to depolarize myenteric neurons over an 8‐hour test period in vitro. The effects of veratridine were monitored electrophysiologically and correlated with the ability of the drug to affect the density of the cytochrome oxidase reaction product, as well as the proportion of reactive myenteric neurons. The action of veratridine on cytochrome oxidase activity was evaluated by means of video microdensitometry and computer‐assisted morphometry. Effects of veratridine were considered to be specific if they were blocked by the inclusion of tetrodotoxin (TTX), which antagonizes the action of veratridine on voltage‐dependent Na+ channels. Veratridine (1.0 μM) depolarized the membranes of myenteric type II neurons and greatly increased both the average density of the cytochrome oxidase reaction product in individual neuronal cell bodies and the proportion that were reactive. The concentration‐effect relationship for veratridine was biphasic. As the concentration of veratridine was raised, neurons became sufficiently depolarized such that they ceased to fire action potentials. This absence of spiking was associated with a decline in the stimulation of cytochrome oxidase activity by veratridine. At still higher concentrations of veratridine the degree of neuronal depolarization continued to increase. This further depolarization was associated with a secondary increase in cytochrome oxidase activity. All effects of veratridine were blocked by TTX. It is concluded that the cytochemical demonstration of cytochrome oxidase reflects the recent metabolic history and thus the physiological activity of myenteric neurons. In control preparations, fixed without exposure to veratridine, considerable variation in cytochrome oxidase was observed between ganglia and between individual neurons within ganglia. This suggests that there are significant differences in the activity of individual ganglia and neurons of the myenteric plexus. These observations support the hypothesis that there is a functional heterogeneity that corresponds to an anatomical heterogeneity (previously demonstrated) of the myenteric plexus.
Dopaminergic projection from nucleus raphe dorsalis to neostriatum in the rat
Authors: Descarries Laurent , Berthelet France , Garcia Sylvia , Beaudet Alain
Published: January 2005

The existence of a dopamine (DA) projection from nucleus raphe dorsalis (RD) to neostriatum was demonstrated in the rat by combined tyrosine hydroxylase (TH) immunohistochemistry and radioautography after retrograde axonal transport of [3H]noradrenaline ([3H]NA). Intrastriatal injections of [3H]NA were carried out in normal rats or after ipsilateral destruction of the nigrostriatal DA system by injection of 6‐hydroxydopamine (6‐OHDA) into the substantia nigra. Some 1,000 TH‐positive nerve cell bodies were counted within the confines of RD as defined by its content in serotonin (5‐HT) neurons. These DA neurons occupied the upper third of the RD and the, were part of its small cell population. In all cases, a small proportion of the TH‐immunoreaative nerve cell bodies in RD were retrogradely radiolabeled. Radiolabeled but immunonegative cells were exceedingly rare. The double‐labeled neurons were generally more numerous after elimination of the nigrostriatial DA innervation than in normal rats. They mostly lay within the ventral portion of the medial subdivision of RD and always predominated on the [3H]NA‐ injected side. Some were also present in nucleus linearis caudalis. It was concluded that (1) [3H]NA had been taken up and retrogradely transported exclusively by catecholamine neurons; (2) part of the DA cell group in RD projects to the neostriatum; and that (3) most if not all non‐5‐HT neurons projecting from RD to neostriatum are likely to be dopaminergic.
Anatomical and physiological observations on suprapinal control of bladder and urethral sphincter muscles in the cat
Authors: Holstege Gert , Griffiths Derek , De Wall Hans , Dalm Eddie
Published: January 2005

In 15 cats injections of 3H‐leucine were made in the pontine tegmentum. Injections in the medial part of the dorsolateral pontine tegmentum (M‐region) resulted in specific projections to the sacral intermediomedial and intermediolateral cell groups. The intermediolateral cell group contains preganglionic parasympathetic neurons that form the motor supply of the detrusor muscle of the bladder. Injections in the lateral part of the pontine tegmental field (L‐region) produced labeled fibers in the nucleus of Onuf, which contains motoneurons innervating the pelvic floor including the anal and urethral sphincters. L‐region projections to the sacral preganglionic parasympathetic neurons and M‐region projections to the nucleus of Onuf were very limited or absent.

In 12 cats physiological experiments were performed. Electrical stimulation in the L‐region elicited a prompt increase in the pelvic floor EMG and urethral pressure but had little influence on the intravesical pressure. Stimulation in the M‐region elicited a prompt decrease in the pelvic floor EMG and urethral pressure followed, after a delay of 2 seconds, by an increase in the intravesical pressure, so simulating normal micturition.
The organization of the reciprocal connections between the subiculum and the entorhinal cortex in the cat: I. A neuroanatomical tracing study
Authors: van Groen T. , van Haren F. J. , Witter M. P. , Groenewegen H. J.
Published: January 2005

The connections between the subiculum (SUB) and the entorhinal cortex (EC) were studied in the cat with retrograde and anterograde tracing techniques.

Injections of the retrogradely transported tracer WGA‐HRP at different levels along the septotemporal axis of the subiculum result in labeled neurons predominantly in the medial entorhinal cortex (MEA) in the superficial layers II and III. In the deep layers labeled cells are found more widespread over the EC. The superficially located labeled EC neurons are topographically distributed in a lateromedial gradient, which corresponds to a septotemporal gradient along the longitudinal axis of the subiculum. This organization of the EC‐SUB projection system could be substantiated by the use of injections anterogradely transported radioactively labeled amino acids in EC.

The SUB to EC projections were investigated with the anterograde transport of WGA‐HRP and with radioactively labeled amino acids that were injected at different levels along the septotemporal axis of the subiculum. This results in a patch of anterogradely labeled fibers and terminals in MEA, predominantly in layers II and III, with a wider band of label in the deep layers. Again, a topographical distribution along the lateromedial axis of the EC corresponding to the septotemporal axis of the SUB was observed.

Contralateral reciprocal connections between EC and SUB are also present, and exhibit a similar topographical organization.
Organization of tyrosine‐hydroxylase immunopositive neurons in the brian of the crested newt, Triturus cristatus carnifex
Authors: Franzoni M. F. , Thibault J. , Fasolo A. , Martinoli M. G. , Scaranari F. , Calas A.
Published: January 2005

The localization of neurons, fibers and terminals containing tyrosine hydroxylase (TH)‐like immunrectivety was stuided in the brain of the crested newt by using an antiserum to rat phaechromocytoma tyrosine hydroxylase. Immunoreactive cells and fibers were found in the spinal cord, the medulla oblongate (lateral periventricular areas), and the aceustolateral area. In the tegmentum mesencephali, two bilaterl clusters of labelled cells were localized in the ventrolateral periventrilcular gray extending toward the caudal hypothalamus. In the hypothalamic tuberal lobes, the TH‐like reactive nurons, frequently of CSF‐contacting type, lined the dorsal wall lof the lateral linfundibular recesses. A thick network of TH‐like reactive nerve fibers and terminals was observed in the percascular zone of the median emience and in the adenohypophysial pars intermedia. A number of labelled cell bodies were also found in the dorsal thalamus (pars intercalaris diencephali), the paraventricular organ, and the ventral wall of the preoptic recess. In the telencephalon, immunoreactive innervatkion was indentified in the striatum, together with immunoposite cell bodies in the olfactory bulbs. The pattern of organization of TH‐immunoreactive sytems in the newt showed, except for some peculiarities (e.g., the labelled cell bodies in dorsal thalamus), close similarities to the arrangement typical of mammals.
GABA‐immunoreactive neurons in the rat cerebellum: A light and electron microscope study
Authors: Gabbott P. L. A. , Somogyi J. , Stewart M. G. , Hamori J.
Published: January 2005

An antibody raised against γ ‐ amino‐butyric acid (GABA) coupled to bovine serum albumin with glutaraldehyde (Hodgson et al: J. Histochem. Cytochem. 33:229–239, '85) was used to localise immunocytochemically the presumptive GABAergic neuronal elements in the cerebellar cortex of the adult rat.

Employing the unlabelled antibody enzyme method with pre‐ and postembedding immunocytochemical procedures, the following cellular structures were observed to be GABA‐immunopositive in both the light and electron microscopes: the somata, dendrites, and axonal processes (including axon terminals) of stellate, basket, and Golgi neurons. In immunopositive neuronal somata and dendrites, the reaction product was found to be associated with all intracellular organelles and with the postsynaptic densities of synaptic junctions. Specific GABA‐like immunoreactivity was also seen around outer mitochondrial membranes, microtubules, and neurofilaments, and coating synaptic vesicles in presynaptic axon terminals.

In the pre‐embedding procedure with dilutions of the antiserum between 1:1,000 and 1:2,000, the perikarya and dendrites of Purkinje cells were GABA‐immunonegative, whereas at an antiserum dilution of 1:500 the somata of Purkinje cells were mildly GABA‐immunoreactive. Purkinje cell axon terminals in the infra‐ and supraganglionic plexuses and in the deep cerebellar nuclei were always strongly immunopositive. Neuroglia were invariably GABA‐immunonegative, as were the dendrites, axons (parallel fibres), and somata of granule cells. Mossy fibre and climbing fibre afferents were also immunonegative.

The pattern of immunoreactivity obtained with this antiserum directed against the inhibitory neurotransmitter GABA was found to resemble closely the immunocytochemical distribution of GABA and of the GABA‐synthesizing enzyme glutamic acid decarboxylase (GAD) as reported previously in other immunocytochemical investigations (Oertel et al. and Wu et al: Cytochemical Methods in Neuroanatomy. New York: A. R. Liss, '82; Seguela et al: Neuroscience 16:865–874, '85; Mugnaini and Oertel: GABA and Neuropeptides in the CNS. Handbook of Chemical Neuroanatomy. Vol. 4, Part I. Amsterdam: Elsevier, '85):.
Ventral posterior visual area of the macaque: Visual topography and areal boundaries
Authors: Newsome William T. , Maunsell John H. R. , van Essen David C.
Published: January 2005

Using both physiological and anatomical techniques, we have studied the topographic organization of extrastriate visual cortex on the ventral surface of the occipital lobe in macaque monkeys. Our results show that a topographically organized representation of the superior contralateral quadrant of the visual field lies immediately anterior to the ventral half of V2. This area is organized in a mirror symmetric fashion to ventral V2: it shares a horizontal meridian representation with V2 and a representation of the superior vertical meridian forms its anterior border. A well‐defined strip of callosal inputs runs along the vertical meridian representation, thereby providing a reliable anatomical marker for areal boundaries in ventral extrastriate cortex. We refer to this area as the ventral posterior area (VP) because it is, in all these respects, notably similar to VP in the owl monkey. Ventral V2 has strong reciprocal connections with VP, and the topography of the V2 projection agrees closely with the topography revealed in our physiological mapping experiments. The visual field representation in VP is strikingly anisotropic, with linear magnification factor being much larger along contours of constant polar angle than along contours of constant eccentricity.
A comparative light microscopic analysis of the sensory innervation of the mystacial pad. I. Innervation of vibrissal follicle‐sinus complexes
Authors: Rice Frank L. , Mance Ajuan , Munger Bryce L.
Published: January 2005

This comparative study was conducted (1) to provide a detailed, comprehensive description of the innervation to the follicle‐sinus complex (F‐SC) of mystacial vibrissae and (2) to determine if interspecies variability in the innervation of the F‐SCs may be related to differences in the structure or existence of barrels in the primary somatosensory (SI) cortex. Two silver techniques (Winkelmann on 100μm‐thick‐frozen sections and Sevier‐Munger on 8μ‐thick paraffin sections) were applied to comparable mystacial skin samples from adult hamsters, mice, rats, gerbils, rabbits, guinea pigs and cats.

The basic structure and innervation of the F‐SCs is the same in all species. Six distinct populations of sensory receptors are identified at consistent locations: (1) Merkel endings in the epidermal rete ridge collar at the mouth of the follicle; (2) circularly disposed presumptive lanceolate, Ruffini, and free nerve endings (FNE) in the inner conical body; (3) longitudinal lanceolate endings in a dense palisade in the mesenchymal sheath at the level of the ring sinus; (4) Merkel endings in the external root sheath at the level of the ring sinus; (5) scattered corpuscular and FNEs (possibly lanceolate or Ruffini endings) in the cavernous sinus; and (6) a few FNEs in the dermal papilla. In each F‐SC, the first two locations are supplied by several superficial vibrissal nerves that arise from several small nerves that also innervate the skin between the vibrissae. These superficial nerves may innervate more than one F‐SC. The next three locations are supplied by a single large deep vibrissal nerve that is derived directly from a row fascicle of the infraorbital nerve. Each deep nerve innervates a single F‐SC. The source of the papilla innervation was not found.

The ring sinus locations are consistently the most heavily innervated in all species. The number of axons in comparable deep vibrissal nerves is similar among the rodents, higher in the cat, and lower in the rabbit. Innervation of the inner conical body varies considerably, being dense in species that vigorously whisk their vibrissae (hamster, mouse, rat, and gerbil) and sparse or absent in species that minimally or never whisk (guinea pig, rabbit, and cat). Innervation to the cavernous sinus is aparse particularly in hamsters and gerbils. The innervation to the rete ridge is uniquely absent in the rabbit. In spite of these differences, there was no apparent correlation between the F‐SC innervation and the structure or absence of barrels. The function of the F‐SC receptors is considered based upon (1) the consistency of receptor distribution in relation to specific structural features of the F‐SCs, (2) interspecies differences in F‐SC innervation, and (3) physiological observations published by other investigators.
Postnatal development of afferent projections to the lateral suprasylvian visual area in the cat: An HRP study
Authors: Kato Nobuo , Kawaguchi Saburo , Miyata Hirofumi
Published: January 2005

The postnatal development of thalamic and cortical projections to the medial bank of the lateral suprasylvian area was studied in the cat by using the retrograde and orthograde HRP methods. Both projections are already present at birth. In both newborn kittens and adult cats, the thalamic projections arise from the same nuclei. By far the heaviest thalamic projections originates from a relatively lateral portion of the lateral posterior nucleus (the presumed LP1)

The cortical laminar distribution of the afferents arising from the presumed LP1 changes markedly with aging. In kittens younger than 1 week, the terminals are distributed densely in layer I and sparsely in layer IV. With age, the terminals in layer I become less dense while those in layer IV become denser. By 1 month of age, the terminal distribution is similar to that found in adult cats, in which the terminals are sparse in layer I and dense in depth‐‐‐particularly, in layer IV.

The terminal distribution of the corticocortical projections from areas 17 and 18 also changes with aging. The terminals in kittens younger than 2 weeks are distributed in both superficial and deep cortical layers, whereas those in kittens older than 1 month and in an adult cat are distributed only in deep layers.
Immunohistochemical identification of noradrenaline‐ and adrenaline‐synthesizing neurons in the cat ventrolateral medulla
Authors: Ciriello John , Caverson Monica M. , Park Dong H.
Published: January 2005

The distribution and morphology of cell bodies containing the catecholamine biosynthetic enzymes dopamine‐β‐hydroxylase (DBH) and phenylethanolamine N‐methyltransferase (PNMT) in the ventrolateral medulla (VLM) of the cat were studied immunohistochemically after intracisternal administration of colchicine. Perikarya immunoreactive to DBH were found throughout the VLM extending from approximately the spinomedullary junction to the level of the superior olivary nucleus. In the caudal VLM DBH neurons were found primarily in the region immediately dorsal to the lateral reticular nucleus (LRN), although a few scattered DBH neurons were also found near the ventral surface of the medulla in and around the parvicellular division of the LRN. These DBH neurons in the caudal VLM were generally fusiform, fusiform‐bipolar, or multipolar, with a mean somal area of 422 ± 32 μm2, and with two to four branching processes. In the rostral VLM DBH neurons formed three distinct groups: one group was found in the nucleus paragigantocellularis lateralis in the region just ventromedial to the retrofacial nucleus (RFN) near the ventrolateral surface of the medulla; the second group was found in the region dorsomedial to the rostral aspects of the nucleus ambiguus and the RFN, and the third group was found in the region along the lateral aspect of the superior olivary nucleus.

Perikarya immunoreactive to the adrenaline‐synthesizing enzyme PNMT were localized to a more restricted region of the VLM that extended from approximately the rostral aspect of the caudal third of the inferior olivary complex (level of the obex) to the caudal pole of the facial nucleus. These PNMT neurons were fusiform or multipolar with a mean somal area of 273 ± 21 μm2, and with two to five branching processes. The location, size, shape, and numbers of PNMT‐immunoreactive neurons corresponded closely to the rostral groups of DBH neurons, with the exception of the group found along the lateral aspect of the superior olivary nucleus. These data indicate that noradrenaline‐synthesizing neurons are primarily found in the caudal VLM and in the region near the superior olivary nucleus, whereas catecholamine neurons in the rostral VLM between these two noradrenergic cell groups synthesize adrenaline. As the VLM has previously been shown to have direct connections with spinal cord, brainstem, and hypothalamic areas implicated in cardiovascular and neuroendocrine regulation, this suggests that DBH‐ and PNMT‐synthesizing neurons are components of neuronal circuits involved in these homeostatic mechanisms.
Cholinergic neurons of the laterodorsal tegmental nucleus: Efferent and afferent connections
Authors: Satoh K. , Fibiger H. C.
Published: January 2005

The ascending projections of cholinergic neurons in the laterodorsal tegmental nucleus (TLD) were investigated in the rat by using Phaseolus vulgaris leucoagglutinin (PHA‐L) and wheat germ agglutinin‐conjugated horseradish peroxidase (WGA‐HRP) anterograde tracing techniques. Two ascending pathways were identified after iontophoretic injections of PHA‐L into the TLD. A long projection system courses through the dorsomedial tegmentum, caudal diencephalon, medial forebrain bundle, and diagonal band. Different branches of this system innervate the midbrain (superior colliculus, interstitial magnocellular nucleus of the posterior commissure, and anterior pretectal nucleus), the diencephalon (lateral habenular nucleus, parafascicular, anteroventral, anterodorsal, mediodorsal, and intralaminar thalamic nuclei), and the telencephalon (lateral septum and medial prefrontal cortex). The second system is shorter and more diffuse and innervates the median raphe, interpeduncular, and lateral mammillary nuclei. Retrograde tracing with WGA‐HRP, combined with choline acetyltransferase immunohistochemistry, revealed that most of the TLD projections to the tectum, pretectum, thalamus, lateral septum, and medial prefrontal cortex are cholinergic.

Afferents to the TLD were studied by anterograde and retrograde tracing techniques. Injection of tracers into the TLD retrogradely labelled neurons bilaterally in the midbrain reticular formation, the periaqueductal gray, the medial preoptic nucleus, the anterior hypothalamic nucleus, and the perifornical and lateral hypothalamic areas. Retrogradely labelled cells were also located bilaterally in the premammillary nucleus, paraventricular hypothalamic nucleus, zona incerta, and lateral habenular nucleus. In the telencephalon, the nucleus of the diagonal band and the medial prefrontal cortex contained retrogradely labelled neurons ipsilateral to the TLD injection site. The projections of the medial prefrontal cortex, the bed nucleus of the stria terminalis, and the lateral habenular nucleus to the TLD were confirmed in anterograde tracing studies.

These findings indicate that the TLD gives rise to several ascending cholinergic projections that innervate diverse regions of the forebrain. Afferents to the TLD arise in hypothalamic and limbic forebrain regions, some of which appear to have reciprocal connections with the TLD. The latter include the lateral habenular nucleus and medial prefrontal cortex.
Organization of atriopeptin‐like immunoreactive neurons in the central nervous system of the rat
Authors: Standaert David G. , Needleman Philip , Saper Clifford B.
Published: January 2005

The atrial natriuretic peptide, atriopeptin, is a circulating hormone that plays an important role in the regulation of fluid and electrolyte homeostasis. Several recent studies have shown that atriopeptin‐like immunoreactivity is present within the central nervous system as well as peripheral tissues. In the present report, we describe in detail the organization of atriopeptin‐like immunoreactive (APir) perikarya and fibers in the central nervous system of the rat. The most prominent collection of APir perikarya was found in the hypothalamus, adjacent to the anteroventral tip of the third ventricle. Additional groups of APir perikarya were observed along the wall of the third ventricle and in the paraventricular and arcuate nuclei. Separate, smaller groups with distinctive morphology were seen in the lateral hypothalamic area, in the supra‐mammillary, medial, and lateral mammillary nuclei, medial habenular nucleus, bed nucleus of the stria terminalis, and the central nucleus of the amygdala. In the pons and brainstem, APir neurons were observed in the pedunculopontine and laterodorsal tegmental nuclei, as well as in the ventral tegmental area, Barrington's nucleus, the parabranchial nucleus, and the nucleus of the solitary tract. The densest terminal fields of APir fibers were found in the paraventricular nucleus of the hypothalamus, the bed nucleus of the stria terminalis, the median eminence, and the interpeduncular nucleus.

The presence of atriopeptin immunoreactivity within the central nervous system suggests that atriopeptin may function as a central neuromediator. Potential functions of this candidate neuromediator deduced from its anatomical distribution are discussed, including the possibility that atriopeptin may function as both a central neuromediator and a systemic hormone in the regulation of the cardiovascular system.
Quantitative cytoarchitectonics of the posterior cingulate cortex in primates
Authors: Zilles Karl , Armstrong Este , Schlaug Gottfried , Schleicher Axel
Published: January 2005

The cytoarchitecture of four cortical areas within the posterior cingulate region and the differences among them are quantitatively analyzed in 17 primate species. The transition from allocortex (area 29) to isocortex (areas 30, 23, and 31) is characterized by shifts in laminar proportions and cellular densities. The molecular layer and inner main lamina (layers V and VI) occupy a smaller proportion of the cortex in iso‐ than in allocortex, while conversely, the outer main lamina (layers II and III) makes up a larger proportion of the cortex in iso‐ than in allocortex. Layer IV is relatively larger in area 31 than in area 23. The packing densities of cell bodies were determined by gray‐level index values. These values show that the isocortex has lower cell densities in the outer main lamina, but higher cell densities in the inner main layers. Furthermore, the granular layer of area 31 is more densely packed than it is in area 23. These results are discussed as structural correlates of a relative increase in the receptive and processing capacities of the isocortex over the adjacent allcortex.
Laminar and synaptic organization of the projection from the thalamic nucleus centralis to primary visual cortex in the cat
Authors: Cunningham Emmett T. , Levay Simon
Published: January 2005

The projection from the nucleus centralis (an intralaminar thalamic nucleus) to the primary visual cortex was examined with anterograde and retrograde tracing techniques. After large injections of horseradish peroxidase into areas 17 and 18 almost one‐half of the neurons in the nucleus centralis were retrogradely labeled. An injection of 3H‐proline into the nucleus centralis led to sparse anterograde labeling in layers 5 and 6 of areas 17 and 18. Large injections of peroxidase‐conjugated wheat germ agglutinin (WGA) into the nucleus centralis led to similar anterograde labeling of layers 5 and 6 and, in addition, to a band in layer 1. No retrogradely labeled cells were seen in areas 17 or 18. The WGA‐labeled terminals in area 17 were examined in the electron microscope: they formed type 1 (asymmetric) synapses on dendritic spines. These observations suggest that the afferents from the nucleus centralis primarily contact pyramidal cells that project to subcortical targets. The findings are consistent with physiological studies suggesting that the nucleus centralis is involved in the modulation of cortical outflow with varying levels of arousal.
Localization of γ‐aminobutyric acid (GABA) in type 3 cells and demonstration of their source to f2 terminals in the cat lateral geniculate nucleus: A golgi‐electron‐microscopic GABA‐immunocytochemical study
Authors: Montero V. M.
Published: January 2005

Postembedding immunocytochemistry with a γ‐aminobutyric acid (GABA) antiserum was done on semithin sections of cat lateral geniculate nucleus (LGN) previously processed with the rapid‐Golgi and gold‐toning procedures, to determine which of the three main morphological types (1,2,3) of neurons in the A‐laminae show immunoreactivity and are, therefore, presumably GABAergic. Only type 3 cells were found to be GABA positive. These cells were characterized by small somata and few, scarcely branched dendrites bearing almost exclusively appendages with long slender stalks. Some of these cells have extensive filiform “axonlike” processes originating from different regions of dendrites and having appendages similar to those originating directly from dendrites. Many of these Golgi gold‐toned impregnated dendritic appendages of type 3 cells were analyzed in the electron microscope and were identified as typical F2 terminals by (1) their content of pleomorphic synaptic vesicles; (2) by being postsynaptic to retinal (RLP), cortical (RSD), and perigeniculate (F1) terminals; and (3) by being presynaptic to dendrites. In addition, since it was previously demonstrated that glutamic acid decarboxylase (GAD) and GABA‐positive cells are not retrogradely labeled with horseradish peroxidase (HRP) from the visual cortex, the present results, by showing that GABA‐positive cells have type 3 morphology, provide supporting evidence for the interneuronal nature of type 3 cells in cat LGN.
Ultrastructural features and hormone‐dependent sex differences of mormyrid electric organs
Authors: Bass Andrew H. , Denizot Jean‐Pierre , Marchaterre Margaret A.
Published: January 2005

The electric organ of mormyrid fishes is composed of action potentialgenerating cells called electrocytes that together produce a species‐typical electric organ discharge (EOD). The electrocytes of mormyrids are discshaped cells with distinct anterior and posterior faces, and a series of evaginations of one face that form a stalklike structure that is the site of innervation by spinal electromotoneurons (Bass: J. Comp. Neurol. 244:313–330, '86a). Here, we describe the major ultrastructural features of mormyrid electrocytes, which include surface invaginations along each face, myonuclei, myofilaments, and neuromuscularlike junctions formed by the axons of spinal electromotoneurons. The degree of surface invaginations along the anterior face is the most dramatic interspecific variable and is usually greater for species with the longer duration EODs. Among species with sexually dimorphic EODs, natural males, or females trated with gonadal steroid hormones, have longer‐duration EODs and thicker electrocytes with more surface invaginations along the anterior face. The results are discussed in relation to the action potential‐generating properties of the electrocyte's membranes.
Membrane area and dendritic structure in type‐identified triceps surae alpha motoneurons
Authors: Cullheim S. , Fleshman J. W. , Glenn L. L. , Burke R. E.
Published: January 2005

The size and branching structure of the dendritic tree were studied in nine type‐identified triceps surae α‐motoneurons that were labeled intracellularly with horseradish peroxidase and reconstructed from serial sections in the light microscope. The average total membrane area (AN) for motoneurons of type S (slow‐twitch) motor units was about 22% smaller than AN for cells of type F units (including both FF and FR motor unit types in this category) (480.1 × 103μml;m2 vs. 617.7 ×103 μm2, respectively). Systematic correlations were found between stem dendrite diameter and three measures of dendritic size: dendrite membrane area, combined dendritic length, and number of terminations. All of these correlations were significantly different for the dendrites of F and S montoneurons. Power‐function relations between stem diameter and dendritic membrane area were used to estimate AN for a sample of 79 type‐identified motoneurons. Mean estimated AN values were significantly different for the F and S motoneuron groups, despite a large overlap in AN values between these groups.

The branching structure of dendrites of F and S motoneurons also showed clear differences. Type S motoneuron dendrites showed less‐profuse branching and a more‐even radial distribution of branch points than found in type F cells. Examination of two forms of the “3/2 power rule” for the relation between the diameters of parent and daughter dendritic branches at branch points showed that the dendrites of type S motoneurons conform less well with the anatomical constraints necessary to represent binary branching trees as equivalent cylinders than do dendrites of type F cells. There was no systematic difference between F and S motoneuron dendrites in the degree of asymmetry of first‐order daughter trees. The results overall indicate that the dendrites of F and S motoneuron groups are structurally different, giving rise to a systematic difference in AN between these groups. Such structural differences suggest that the F and S groups of α‐motoneurons can be viewed as intrinsically distinct cell types and not just large vs. small variants of the same cell species.
Three‐Dimensional architecture of dendritic trees in type‐identified α‐motoneurons
Authors: Cullheim S. , Fleshman J. W. , Glenn L. L. , Burke R. E.
Published: January 2005

We have studied the spatial distribution of dendrites of type‐identified triceps surae α‐motoneurons, labeled intracellularly with HRP, using a variety of analytical approaches that were designed to quantify the ways in which dendrites occupy three‐dimensional space. All of the methods indicated a strong tendency for motoneuron dendrites to project radially. However, regions dorsal and ventral to the somata contained fewer dendritic elements, and less membrane area, than expected for complete radial symmetry. Individual dendrites projecting into these regions tended to be smaller than those projecting rostrocaudally or mediolaterally. Nevertheless, the center of mass of membrane area for five of six fully analyzed cells was within 100 μm of the soma and, in all six cells, was located in the same dorsoventral plane as the cell soma. Maps of the projection of dendritic branches onto concentric shells at various radial distances from the soma showed that some regions have high concentrations of branches, sometimes with considerable overlap between branches arising from different stem dendrites, while other regions have relatively few branches, or none at all. Each motoneuron exhibited a different pattern of projection and there were no systematic differences between fast‐twitch (type F, including both types FF and FR units) and slow‐twitch (type S) motoneurons evident in the patterns of dendritic concentration. Assessment of the three‐dimensional territories of individual dendrites showed that dendrites with larger numbers of terminal branches tended to have larger spatial territories. Despite considerable scatter, the results suggest that the density of branches tends to be approximately the same in large and small dendrites, and in F and S cell groups. The results are discussed in relation to the spatial location of synaptic input to motoneurons.
Distribution of luteinizing hormone‐releasing hormone in the nervus terminalis and brain of the mouse detected by immunocytochemistry
Authors: Schwanzel‐Fukuda Marlene , Garcia Maria Soledad , Morrell Joan I. , Pfaff Donald W.
Published: January 2005

Immunoreactive luteinizing hormone‐releasing hormone (LHRH) was localized in a relatively large number of ganglion cells and fibers of the nervus terminalis of neonatal and adult mice, indicating that this nerve is a substantial source of LHRH in the mouse brain.

Whole‐head specimens of neonatal mice, prior to calcification of the cranium, revealed an extensive distribution of LHRH neurons and fine fibers throughout the peripheral, intracranial, and central parts of the nervus terminalis. The most striking difference between the neonatal and adult animals, in the nervus terminalis, was the increase in immunoreactive axons that made up the fiber bundles of this nerve. In the adult mouse, the intracranial and central projections were composed of thick fascicles of immunoreactive axons, ensheathed by glial cells and accompanied by ganglia that contained both LHRH‐reactive and nonimmunoreactive neurons. LHRH‐immunoreactive cells and axons were seen in a branch of the nervus terminalis that coursed along the medial, posterodorsal aspect of the olfactory bulb and in branches of this nerve that accompany the vomeronasal nerves to the accessory olfactory bulb. A few LHRH neurons and many immunoreactive processes were seen in the accessory and main olfactory bulbs.

LHRH‐reactive neurons were seen in the hypothalamus and extrahypothalamic structures. Examination of adult mouse brains revealed a pattern of distribution and number of immunoreactive neurons similar to that seen in the neonate. However, many more LHRH‐reactive axons were seen in all areas of the brain of the mature animal.
Somatosensory nuclei in the brainstem of the rat: Independent projections to the thalamus and cerebellum
Authors: Mantle‐St. John Louise A. , Tracey David J.
Published: January 2005

The dorsal column nuclei and the sensory trigeminal nuclei project not only to the ventrobasal thalamus but also to the cerebellum. In this study the numbers and distribution of neurones projecting to these two regions were examined for the following nuclei: the rostral part of the main cuneate nucleus, the external cuneate nucleus, nucleus x, the principal sensory nucleus of the trigeminal nerve, and the oral, interpolar, and caudal subnuclei of the spinal nucleus of the trigeminal nerve.

A thalamic projection from nucleus x and from the external cuneate nucleus was confirmed, and a distinct group of neurones projecting to the ventroposteromedial thalamus was distinguished near the ventromedial aspect of the principal sensory nucleus.

Of the 165,000 neurones examined, only one was found to be double labelled. It was concluded that the populations of neurones that project to the ventrobasal thalamus and to the cerebellum are separate, and that somatosensory neurones in the brainstem do not send axon collaterals to both regions.
A quantitative study of morphological reorganization following chronic optic deafferentation in the adult cat dorsal lateral geniculate nucleus
Authors: Somogyi J. , Eysel U. , Hamori J.
Published: January 2005

Neuronal and synaptic reorganization in the lateral geniculate nucleus (dLGN) of adult cats following chronic visual deafferentation has been investigated with the aid of GABA immunocytochemistry and quantitative electron microscopy. The main purpose of this study was to establish the morphological counterpart of the functional plasticity of dLGN relay cells after total visual deafferentation (Eysel: Brain Res. 166:259–271, '79). The results provide evidence that the regained excitability of relay cells is not the result of disinhibition (caused hypothetically by the selective loss of GABAergic cells) since the proportion of GABA‐positive and GABA‐negative cells as well as the inhibitory synaptic density did not change. The alternative suggestion that the enhanced excitability could be the result of compensatory axonal sprouting by corticothalamic fibers had also to be dropped: the absolute number of corticothalamic axons to the deafferented dLGN remains unchanged. Because of shrinkage of the dendritic trees of dLGN neurons, however, the density of cortical synaptic input at dLGN cells becomes elevated by almost 60%. It is suggested that the regained excitability of relay neurons is the consequence of the combined effects of (1) adaptive (structural) reduction in size (“atrophy”) of retinally denervated nerve cells, and, as a consequence, (2) increase of input resistance, (3) reduced shunting effects, and (4) relative increase in density of the excitatory cortical input per neuron.
Analysis of the habenulopetal enkephalinergic system in the rat brain: An immunohistochemical study
Authors: Shinoda Koh , Tohyama Masaya
Published: January 2005

The enkephalinergic afferent system in the rat habenula was examined by the indirect immunofluorescence method with antibodies against leucine‐enkephalin.

Leucine‐enkephalin‐like immunoreactive (L‐ENKI) fibers were observed in the dorsal portion of the medial habenular nucleus (MHb), the intermediate portion of the lateral habenular nucleus (LHb), and the border zone between the MHb and the LHb (BZHb).

Knife‐cut studies demonstrated that almost all the fibers were supplied via the stria medullaris. Also two discrete ENKergic afferents to the MHb and the LHb were found by several kinds of lesion studies: (1) the MHb was ipsilaterally innervated from L‐ENKI neurons in “septoperiventricular area,” which is the junctional area between the ventral supracommissural septum and the rostral thalamic periventricular region. (2) The LHb was ipsilaterally innervated from L‐ENKI neurons in the rostral portion of the lateral hypothalamus. Our findings also suggested that the L‐ENKI fibers in the BZHb are supplied via the stria medullaris with an ipsilateral predominance and that, at the most caudal level, they arise not only from the ipsilateral stria medullaris but also from the contralateral stria medullaris via the habenular commissure.
Immunocytochemical localization of GABA‐, cholecystokinin‐, vasoactive intestinal polypeptide‐, and somatostatin‐like immunoreactivity in the area dentata and hippocampus of the rat
Authors: Sloviter Robert S. , Nilaver Gajanan
Published: January 2005

Hippocampal neurons containing GABA‐, cholecystokinin(CCK)‐, vasoactive intestinal polypeptide(VIP)‐, or somatostatin(SS)‐like immunoreactivity (LI) were localized in sections of rat hippocampus. GABA‐, CCK‐, VIP, and SS‐LI are found exclusively in interneurons of the area dentata and hippocampus. In the area dentata, GABA‐LI occurs in cells of all strata but predominates in type 1 and 2 basket cells. CCK‐LI is present in a subset of these basket cells and some hilar cells. VIP‐LI is present in a distinct subset of dentate interneurons that, unlike the type 1 and 2 basket cells, do not contribute to the fiber plexus in the inner molecular layer. These VIP‐LI interneurons send their axons to nearby granule cells and form a plexus in the hilus. SS‐LI, although rare in cells of the molecular and granular layers, is present in a large population of hilar interneurons that do not exhibit GABA‐, CCK‐, or VIP‐LI. In area CA3 of the hippocampus, a variety of morphologically diverse interneurons containing GABA‐, CCK‐, VIP‐, or SS‐LI are present in all strata. In area CA1, SS‐LI is present mainly in cells of strata oriens and pyramidale. GABA‐CCK‐ and VIP‐LI interneurons are present in all strata of CA1 but, unlike the SS‐LI cells, are most numerous in strata pyramidale and radiatum. These findings in the area dentata, taken together with those of Kosaka et al. (J. Comp. Neurol. 239:967–969, '85), indicate that two main populations of interneurons can be discriminated on the basis of the substances they contain. One is a group of GABA‐LI cells, some of which also contain CCK‐ and/or VIP‐LI. These cells innervate the granule cells and the second group of interneurons, the SS‐LI hilar cells, which apparently form part of the dentate ipsilateral associational/commissural projections.