bluuebunny/crossref_metadata_2025 huggingface dataset:
Type I corticosteroid receptor‐like immunoreactivity in the rat CNS: Distribution and regulation by corticosteroids
Authors: Ahima Rexford , Krozowski Zygmunt , Harlan Richard E.
Published: January 2005

Previous maps of Type I corticosteroid receptor binding in the rat central nervous system (CNS) revealed a restricted distribution of the receptor in limbic regions, hypothalamus, and circumventricular organs. More recent studies have shown a more widespread expression of the receptor, with high levels of Type I receptor mRNA in limbic, motor, and sensory systems. We have used two antisera against peptide sequences derived from the cDNA of the human Type I corticosteroid receptor to map the regional distribution and corticosteroid regulation of the intracellular location of Type I corticosteroid receptor‐like immunoreactivity (Type I‐ir) in the rat CNS.

Neurons showing Type I‐ir were observed at all levels of the CNS. Highest densities of immunoreactive neurons were observed in limbic regions, isocortex, and some thalamic nuclei. Motor, sensory, and visceral systems often showed moderate densities of immunoreactive neurons. Type I‐ir glia were observed in some fiber systems, e.g., corpus callosum, medial lemniscus, cerebral peduncles, spinal trigeminal tract, and funiculi of the spinal cord. In the majority of neurons and in glia, Type I‐ir showed a diffusely nuclear and cytoplasmic location, Long‐term adrenalectomy reduced immunoreactivity in most neurons and glia. Neuronal Type I‐ir was localized mainly in the cytoplasm after long‐term adrenalectomy. Nuclear immunoreactivity was retained in some neurons in the globus pallidus, motor trigeminal nucleus, and laminae 8 and 9 of the spinal cord. Acute treatment with corticosterone or aldosterone restored neuronal and glial Type I‐ir to densities below that seen in intact rats.
Hypothalamic paraventricular nucleus: A quantitative analysis of cytoarchitectonic subdivisions in the rat
Authors: Kiss Jozsef Zoltan , Martos Janos , Palkovits Miklos
Published: January 2005

The boundaries of subnuclei of the hypothalamic paraventricular nucleus (PVN) were outlined on the basis of a step by step computer‐assisted image analysis of coronal, serial sections of the hypothalamus in rats. The cell size‐frequency histogram, cell packing density, and the cell number were determined for each PVN subdivision. Three principal cell types were distinguished: small, short diameter (d) = 6–10 μm; medium‐sized, d = 10–13 μm; and large, d = 13–19 μm. None of these cell types occur exclusively in any PVN subdivision. According to the predominant cell type, the PVN can be divided into magnocellular, mediocellular and parvicellular subnuclei. Large cells appear to form one subdivision in which the cell packing density is relatively stable. Although the cell sizes showed a relatively large variation, no definitive subgroups (parts) could be distinguished. On the basis of cell packing density, the parvicellular and mediocellular subnuclei can be further divided. The mediocellular cell group can be divided into a dorsal and a posterior subdivision. The parvicellular zone is subdivided into a periventricular and a large medial subdivision. Based on inhomogeneities in cell packing density, the medial subdivision can be further divided into anterior, dorso‐lateral, ventro‐medial and caudal parts.

The estimated total cell number in the PVN (in both sides of the brain) is about 21,500. On average, 19% of this population, i.e., 4,200 neurons, was calculated in the magnocellular (neurosecretory) division. Out of this, only 66%, about 2,700 cells, falls into the category of large cells. There are approximately 5,700 neurons in the posterior and dorsal mediocellular, and about 11,600 in the periventricular and medial parvicellular subdivisions.
A PHA‐L analysis of ascending projections of the dorsal raphe nucleus in the rat
Authors: Vertes Robert P.
Published: January 2005

Ascending projections from the dorsal raphe nucleus (DR) were examined in the rat by using the anterograde anatomical tracer, Phaseolus vulgaris leucoagglutinin (PHA‐L). The majority of labeled fibers from the DR ascended through the forebrain within the medial forebrain bundle. DR fibers were found to terminate heavily in several subcortical as well as cortical sites.

The following subcortical nuclei receive dense projections from the DR: ventral regions of the midbrain central gray including the ‘supraoculomotor central gray’ region, the ventral tegmental area, the substantia nigra‐pars compacta, midline and intralaminar nuclei of the thalamus including the posterior paraventricular, the parafascicular, reuniens, rhomboid, intermediodorsal/mediodorsal, and central medial thalamic nuclei, the central, lateral and basolateral nuclei of the amygdala, posteromedial regions of the striatum, the bed nucleus of the stria terminalis, the lateral septal nucleus, the lateral preoptic area, the substantia innominata, the magnocellular preoptic nucleus, the endopiriform nucleus, and the ventral pallidum. The following subcortical nuclei receive moderately dense projections from the DR: the median raphe nucleus, the midbrain reticular formation, the cuneiform/pedunculopontine tegmental area, the retrorubral nucleus, the supramammillary nucleus, the lateral hypothalamus, the paracentral and central lateral intralaminar nuclei of the thalamus, the globus pallidus, the medial preoptic area, the vertical and horizontal limbs of the diagonal band nuclei, the claustrum, the nucleus accumbens, and the olfactory tubercle.

The piriform, insular and frontal cortices receive dense projections from the DR; the occipital, entorhinal, perirhinal, frontal orbital, anterior cingulate, and infralimbic cortices, as well as the hippocampal formation, receive moderately dense projections from the DR.

Some notable differences were observed in projections from the caudal DR and the rostral DR. For example, the hippocampal formation receives moderately dense projections from the caudal DR and essentially none from the rostral DR. On the other hand, virtually all neocortical regions receive significantly denser projections from the rostral than from the caudal DR.

The present results demonstrate that dorsal raphe fibers project significantly throughout widespread regions of the midbrain and forebrain.
GABAergic interneurons containing calbindin D28K or somatostatin are major targets of GABAergic basal forebrain afferents in the rat neocortex
Authors: Freund Tamás F. , Gulyás A. I.
Published: January 2005

The arborization pattern and postsynaptic targets of the GABAergic component of the basal forebrain projection to neo‐ and mesocortical areas have been studied by the combination of anterograde tracing and pre‐ and postembedding immunocytochemistry. Phaseolus vulgaris leucoagglutinin (PHAL) was iontophoretically delivered into the region of the diagonal band of Broca, with some spread of the tracer into the substantia innominata and ventral pallidum. A large number of anterogradely labelled varicose fibres were visualized in the cingulate and retrosplenial cortices, and a relatively sparse innervation was observed in frontal and occipital cortical areas. Most of the labelled axons were studded with large en passant varicosities (Type 1), whereas the others (Type 2) had smaller boutons often of the drumstick type. Type 1 axons were distributed in all layers of the mesocortex with slightly lower frequency in layers 1 and 4. In the neocortex, layer 4, and to a smaller extent upper layer 5 and layer 6 contained the largest number of labelled fibres, whereas only a few fibres were seen in the supragranular layers. Characteristic type 2 axons were very sparse but could be found in all layers.

Most if not all boutons of PHAL‐labelled type 1 axons were shown to be GABA‐immunoreactive by immunogold staining for GABA, Altogether 73 boutons were serially sectioned and found to make symmetrical synaptic contacts mostly with dendritic shafts (66, 90% of total targets), cell bodies (6, 8.2% of total), and with one spine. All postsynaptic cell bodies, and the majority of the dendritic shafts (44, 60.3% of total targets) were immunoreactive for GABA. Thus at least 68.5% of the total targets were GABA‐positive, but the majority of the dendrites not characterized immunocytochemically for technical reasons (15.1%) also showed the fine structural characteristics of nonpyramidal neurons.

The target interneurons included some of the somatostatin‐ and calbindin‐containing subpopulations, and a small number of parvalbumin‐containing neurons, as shown by double immunostaining for PHAL and calcium‐binding proteins or neuropeptides.

We suggest that the innervation of inhibitory interneurons having extensive local axon arborizations may be a mechanism by which basal forebrain neurons–most notably those containing GABA–have a powerful global effect on the majority of principal cells in the entire cortical mantle.
Central projections of auditory nerve fibers in the barn owl
Authors: Carr C. E. , Boudreau R. E.
Published: January 2005

The central projections of the auditory nerve were examined in the barn owl. Each auditory nerve fiber enters the brain and divides to terminate in both the cochlear nucleus angularis and the cochlear nucleus magnocellularis. This division parallels a functional division into intensity and time coding in the auditory system. The lateral branch of the auditory nerve innervates the nucleus angularis and gives rise to a major and a minor terminal field. The terminals range in size and shape from small boutons to large irregular boutons with thorn‐like appendages. The medial branch of the auditory nerve conveys phase information to the cells of the nucleus magnocellularis via large axosomatic endings or end bulbs of Held. Each medial branch divides to form 3–6 end bulbs along the rostrocaudal orientation of a single tonotopic band, and each magnocellular neuron receives 1–4 end bulbs. The end bulb envelops the postsynaptic cell body and forms large numbers of synapses. The auditory nerve profiles contain round clear vesicles and form punctate asymmetric synapses on both somatic spines and the cell body.
Synaptic inputs to physiologically identified retinal X‐cells in the cat
Authors: Weber A. J. , McCall M. A. , Stanford L. R.
Published: January 2005

The cat retina contains a number of different classes of ganglion cells, each of which has a unique set of receptive field properties. The mechanisms that underlie the functional differences among classes, however, are not well understood. All of the afferent input to retinal ganglion cells are from bipolar and amacrine cell terminals in the inner plexiform layer, suggesting that the physiological differences among cat retinal ganglion cells might be due to differences in the proportion of input that they receive from these cell types.

In this study, we have combined in vivo intracellular recording and labeling with subsequent ultrastructural analysis to determine directly the patterns of synaptic input to physiologically identified X‐cells in the cat retina. Our primary aim in these analyses was to determine whether retinal X‐cells receive a characteristic pattern of bipolar and amacrine cell input, and further, whether the functional properties of this cell type can be related to identifiable patterns of synaptic input in the inner plexiform layer. We reconstructed the entire dendritic arbor of an OFF‐center X‐cell and greater than 75% of the dendritic tree of an ON‐center X‐cell and found that (1) both ON‐ and OFF‐center X‐cells are contacted with approximately the same frequency by bipolar and amacrine cell terminals, (2) each of these input types is distributed widely over their dendritic fields, and (3) there is no significant difference in the pattern of distribution of bipolar and amacrine cell synapses onto the dendrites of either cell type. Comparisons of the inputs to the ON‐ and the OFF‐center cell, however, did reveal differences in the complexity of the synaptic arrangements found in association with the two neurons; a number of complex synaptic arrangements, including serial amacrine cell synapses, were found exclusively in association with the dendrites of the OFF‐center X‐cell.

Most models of retinal X‐cell receptive fields, because their visual responses share a number of features with those of bipolar cells, have attributed X‐cell receptive field properties to their bipolar cell inputs. The data presented here, the first obtained from analyzing the inputs to the entire dendritic arbors of retinal X‐cells, demonstrate that these retinal ganglion cells receive nearly one‐half of their input from amacrine cells. These results clearly indicate that further data concerning the functional consequences of amacrine cell input are needed to understand more fully visual processing in the X‐cell pathway.
The distribution of neuropeptides in the dorsomedial telencephalon of the pigeon (Columba livia): A basis for regional subdivisions
Authors: Erichsen Jonathan T. , Bingman Verner P. , Krebs John R.
Published: January 2005

The distribution of six neuropeptides [substance P (SP), leucine (leu5‐) enkephalin (LANK), vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), neuropeptide Y (NPY), and somatostatin (SS)] in the dorsormedial telencephalon (hippocampal region) of the pigeon was studied by immunohistochemistry.

All six peptides were found in fibers passing through the septo‐hippocampal junction and along the medial wall of the hippocampal region. NPY‐, SS‐, and VIP‐like staining of fibers was seen in the hippocampal commissure. NPY and SS had similar distributions within the hippocampal region, both being most conspicuous in cell bodies, terminals, and fibers of the medial hippocampal region. VIP‐positive cells were found in an area dorsal to the SS/NPY cell region. CCK‐like immunoreactivity was found in terminal baskets surrounding large cells of a v‐shaped structure in the ventromedial hippocampal region. SP‐ and LENK‐like immunoreactivity was found in neuropils in a lateral‐dorsal region, the two substances showing similar distributions. This region is thought to lie lateral to the limit of the hippocampal region.

Parallels with the distribution of immunoreactivity in the mammalian hippocampus are used to suggest possible equivalent subdivisions of the avian and mammalian hippocampal regions.
Selective localization of polyribosomes beneath developing synapses: A quantitative analysis of the relationships between polyribosomes and developing synapses in the hippocampus and dentate gyrus
Authors: Steward Oswald , Falk Paula M.
Published: January 2005

Previous studies have revealed that polyribosomes are selectively localized beneath post‐synaptic sites on central nervous system (CNS) neurons, and are particularly prominent during periods of synapse growth. The present study evaluates whether polyribosomes are most prominent at a consistent time in the developmental history of the synapse, or instead at a consistent time in the life of the organism regardless of the state of synaptic maturation (suggesting a globally acting factor). We compare the time course of synaptogenesis and the association between polyribosomes and developing synapses in three regions that develop at different rates: the external and internal blades of the dentate gyrus, and the CA1 region of the hippocampus proper. Each region was examined electron microscopically at 1, 4, 7, 10, 15, 20, 28 and over 120 days of age, evaluating: (1) synapse density (the number of synaptic profiles/ area of neuropil), (2) the width of the neuropil layers, (3) the proportion of synapses with underlying polyribosomes, and (4) the number of polyribosome‐containing synapses/area of neuropil.

As anticipated on the basis of the differences in cytogenesis, the time course of synaptogenesis was different in the three regions. In the external blade of the dentate gyrus, synapse density increased in a nearly linear fashion between birth and 15 days of age, and then continued to increase at a somewhat slower rate until 28 days of age. Synapse development in the internal blade was delayed by several days in comparison to the external blade. In CA1, synapse density increased slowly between 1 and 7 days, and then at a rapid rate between 7 and 28 days of age. In all three regions, the proportion of synapses with underlying polyribosomes was highest between 1 and 7 days of age, and then decreased as synapse density increased. However, the peak in the number of polyribosome‐containing synapses/unit area of neuropil occurred at different times in the three regions (4–7 days of age in the external blade of the dentate gyrus and in CA1, and 20 days of age in the internal blade). In addition to further defining the relationship between polyribosomes and developing synapses, the present study provides a data base on the time course of synapse development in the hippocampus and dentate gyrus, which will be useful for comparisons with other measures.
Synaptic organization of globular bushy cells in the ventral cochlear nucleus of the cat: A quantitative study
Authors: Ostapoff E.‐Michael , Morest D. Kent
Published: January 2005

The synaptic organization of globular bushy cells of the anteroventral cochlear nucleus was quantitatively analyzed in order to understand better their functional attributes. A method was devised to estimate the concentrations and relative proportions of synapses on the entire postsynaptic surface of Golgi‐impregnated neurons, by sampling with limited series of sections for electron microscopy. This provided a characteristic synaptic profile which was homogeneous for the population measured.

The total concentration of synaptic endings decreases with distance from the soma. The cochlear, presumably glutamatergic and excitatory, endings with large spherical vesicles (LS) account for most of this decrease. Of the noncochlear inputs, the putative glycinergic endings with flattened vesicles (FL) decrease slightly, and the presumed GABAergic terminals with pleomorphic vesicles (PL) maintain a relatively constant concentration, while endings with small spherical vesicles (SS) increase on the distal dendrites. LS endings have the largest proportion of synapses near the soma, while FL synapses maintain a constant proportion in all cell regions, and PL and SS proportions increase on higher‐order dendrites. Excitatory and inhibitory synapses have significant inputs to the axon hillock and initial segment, as well as to the distal dendrites, where dual synapses may provide a way to sample the activity of surrounding neurons.

These features must be considered in explanations of physiological properties, such as the synaptic security, level of spontaneous activity, and well‐timed, rapid onset responses, as well as their potential for normalizing and synchronizing an important inhibitory pathway involved in binaural signal processing. Synaptic profile analysis should be useful for experimental studies and for developing realistic computational models.
Hair cell differentiation in the developing chick cochlea and in embryonic Cochlear organ culture
Authors: Stone Jennifer S. , Cotanche Douglas A.
Published: January 2005

We have defined a method for growing chick embryonic cochleae in organ culture that preserves many aspects of hair cell differentiation. Cochlear ducts were isolated from embryonic day 8 chicks, placed in organ culture, and incubated for 48 hours (to a point equivalent to embryonic day 10). The cultured ducts were then fixed and processed for scanning electron microscopy. As controls, cochlear ducts at embryonic days 8 and 10 were dissected and immediately fixed and processed for scanning electron microscopy. We chose this period to culture cochleae because at the corresponding time in vivo hair cells undergo a dynamic phase of differentation. During this time, the number of stereocilia in the stereociliary bundle increases, and two to three rows of stereocilia nearest the kinocilium elongate, initiating the staircase pattern of the bundle. Also, the orientation of many hair cells shifts from nonpolarized at embryonic day 8 to polarized toward the inferior edge cf the basilar papilla at embryonic day 10. Many of these aspects of hair cell differentiation proceed normally in organ culture. The appropriate distal‐to‐proximal gradients of hair cell density, apical surface area, and stereociliary number are preserved. Elongation of the 1–2 stereociliary rows next to the kinocilium continues, and more stereociliary bundles are oriented toward the inferior edge in cultured cochleae than in embryonic day 8 chicks. It appears that cochlear organ culture can serve as an effective method with which to study how hair cell differentation is regulated.
Classification of the principal cells of the medial nucleus of the trapezoid body
Authors: Kuwabara N. , Zook J. M.
Published: January 2005

Cells in the medial nucleus of the trapezoid body were intracellularly labeled in brainstem tissue slices of two bat and two rodent species. The main cell type found in this nucleus, the principal cell, is an important link in the relay of ascending projections from the contralateral cochlear nucleus to the lateral superior olive, completing an essential pathway for sound localization. Principal cells are often viewed as a highly homogeneous group with a consistent morphology as well as a common function.

Intracellular labeling has revealed a number of new axonal and dendritic features of principal cells. Some of these features vary widely from cell to cell, suggesting that the population of principal cells contains several morphologically distinct subgroups. Similar subsets of principal cells were recognized in all species examined.

Five subgroups were distinguished on the basis of the position of dendritic fields. Although the dendrites of most labeled cells were confined to the medial nucleus of the trapezoid body, some principal cells had dendrites that spread outside the nucleus to one of several adjacent periolivary cell groups. Cells were also found that had dendrites that spread medially across the midline and into the contralateral medial nucleus of the trapezoid body.

Axonal projections were used to distinguish two additional subgroups of principal cells. All principal cells project to the lateral superior olive and virtually all have one or more secondary projections. There are two subgroups with unusual collateral projections: one with collaterals that extended to the lateral lemniscus and one with recurrent collateral axons.
Glial cells of the parietal eye: Structural and biochemical similarities to retinal Müller cells
Authors: Engbretson Gustav A. , Linser Paul J.
Published: January 2005

The parietal eye of lizards is a relatively simple yet highly structured visual organ. Cone‐like photoreceptors synapse directly onto ganglion cells that project to the brain. Golgi staining confirmed the existence of glial cells spanning the sensory epithelium in a manner analogous to the Müller cells of the vertebrate lateral eye retina. These parietal eye glial cells bear expanded end feet at the basal border of the eye. Electron microscopic examination revealed some ultrastructural similarity to Müller cells. Mitochondria, osmiophilic and transparent vesicles, and the Golgi apparatus are found in the apical end of the parietal eye glial cell. Junctional complexes join adjacent parietal eye glial cells and their neighboring photoreceptor cells. Bundles of filaments are found in the basal end of the cell and the plasma membranes of adjacent cells often intertwine tightly in this region. The parietal eye glial cells are immunoreactive to antibodies against glutamine synthetase, also characteristic of Müller cells. Some differences between parietal eye glial cells and Müller cells also are evident. The parietal eye glial cells are not immunoreactive to antibodies against another Müller cell marker, carbonic anhydrase II, and many of them contain melanin granules, while Müller cells are not pigmented. In addition, we have found that the lens cells of the parietal eye and the Müller cells of the lateral eye retina of lizards are immunoreactive to antibodies against both glutamine synthetase and carbonic anhydrase II.
Organization of medullary adrenergic and noradrenergic projections to the periaqueductal gray matter in the rat
Authors: Herbert Horst , Saper Clifford B.
Published: January 2005

The periaqueductal or midbrain central gray matter (CG) in the rat contains a dense network of adrenergic and noradrenergic fibers. We examined the origin of this innervation by using retrograde and anterograde axonal tracers combined with immunohistochemistry for the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), dopamine β‐hydroxylase (DBH), and phenylethanolamine N‐methyltransferase (PNMT). Following injections of the fluorescent tracers Fast Blue or Fluorogold into the CG, double‐labeled neurons in the medulla were identified mainly in the noradrenergic A1 group in the caudal ventrolateral medulla (VLM) and A2 group in the medial part of the nucleus of the solitary tract (NTS); and in the adrenergic C1 group in the rostral ventrolateral medulla and C3 group in the rostral dorsomedial medulla. Injections of Phaseolus vulgaris‐leucoagglutinin (PHA‐L) into these cell groups resulted in a distinct pattern of axonal labeling in various subdivisions of the CG. Anterogradely labeled fibers originating in the medial NTS were predominantly found in the lateral portion of the dorsal raphe nucleus and in the adjacent part of the lateroventral CG (CGlv). Following PHA‐L injections into the C3 region the anterogradely labeled fibers were diffusely distributed in the CGlv and the dorsal raphe nucleus at caudal levels, but rostrally tended to be located laterally in the CGlv. In contrast, ascending fibers from the caudal and rostral VLM terminated in the rostral dorsal part of the CGlv and in the dorsal nucleus of the CG, whereas ventral parts of the CG, including the dorsal raphe nucleus, contained few afferent fibers. Double‐label studies with antisera against DBH and PNMT confirmed that noradrenergic neurons in the A1 and A2 groups and adrenergic neurons in the C1 and C3 groups contributed to these innervation patterns in the CGlv. Noradrenergic and adrenergic projections from the medulla to the CG may play an important role in a variety of autonomic, sensory and behavioral processes.
Development of glutamic acid decarboxylase‐immunoreactive elements in the cerebellar cortex of normal and lurcher mutant mice
Authors: Heckroth John A.
Published: January 2005

The development of glutamic acid decarboxylase‐immunoreactivity (GAD‐IR) in cells, fibers, and varicosities of the cerebellar cortex has been examined by light microscopy in normal and lurcher mutant mice between postnatal day 3 and 30 (P3–P30). Purkinje cell morphology was demonstrated in adjacent sections by using an antiserum to the 28Kd vitamin D‐dependent calcium binding protein (CaBP). In early postnatal lurcher mice, but not in normal littermates, GAD‐IR fibers, presumably Purkinje cell pseudopodia, invade the external granular layer. The plexus of CaBP‐IR axons in the internal granular layer is much less complex in lurcher mice than in normal littermates, even before the onset of lurcher Purkinje cell degeneration at P8. In normal mice, GAD‐IR fibers encapsulate Purkinje cell somata by P15. Lurcher Purkinje cells, in contrast, receive scattered contacts by GAD‐IR puncta and possess a “cap” of such elements surrounding the primary dendrite and apical soma. Pinceau formations, visible as a knot of GAD‐IR puncta hanging from the base of Purkinje cells in normal P15 mice, are not present in lurcher littermates. “Empty baskets” or collapsed pinceau formations in regions devoid of Purkinje cells are not revealed by anti‐GAD immunohistochemistry in the P17–P30 lurcher cerebellar cortex.
Intrinsic circuitry in the cat superior colliculus: Projections from the superficial layers
Authors: Behan M. , Appell P. P.
Published: January 2005

The neuroanatomical tracer Phaseolus vulgaris leucoagglutinin (PHA‐L) was used to label the local projections of neurons whose cell bodies are located in the superficial layers of the cat superior colliculus. Small, localized groups of neurons in the superficial layers project to all regions of the ipsilateral colliculus, including the deep layers. Comparable distributions of labeled terminals are seen throughout the colliculus when the PHA‐L injection site is located in the rostral, middle, or caudal one‐third of the colliculus. In addition, there is some evidence of a topographic projection from superficial to deep layers. These results suggest that a complex anatomical substrate exists for communication between the superficial and deep layers of the colliculus. Connections such as these may underlie the transfer of visual information from neurons in the superficial layers to populations of neurons in the deep layers that respond prior to saccadic eye movements.
Development of the olfactory nerve in the clawed frog, Xenopus laevis: II. Effects of hypothyroidism
Authors: Burd Gail D.
Published: January 2005

Quantitative and morphological data were obtained on developing olfactory axons in normal and hypothyroid larvae of the African clawed frog Xenopus laevis. Hypothyroid larvae were produced by rearing the animals, beginning at stage 48, in a 0.01% solution of propylthiouracil (PTU), a treatment that blocks synthesis of thyroid hormone. These PTU‐treated larvae were compared to their age‐matched siblings when these siblings reached stage 52 (premetamorphic larvae; prior to synthesis of thyroid hormone), stage 57 (late prometamorphic larvae; after the onset of thyroid hormone synthesis), or stage 58 (larvae at the onset of metamorphic climax; thyroid hormone levels continue to rise). The number of olfactory axons did not differ between stage 52 control animals and the age‐matched, PTU‐treated animals, but there were only about half the number of axons in the PTU‐treated animals that were age‐matched to the stage 57 or 58 controls. Thus, PTU had no effect on olfactory axon number prior to the normal rise in thyroid hormone levels. But PTU significantly reduced the normal increase in olfactory axon number compared to stage 58 control larvae, whose thyroid hormone levels are high. While PTU also produced some changes in several other body measurements, the effect on the olfactory axons was the most consistent and prominent. The results presented here support our previous findings that thyroid hormone plays a significant role in the development of the olfactory system in Xenopus.
Functional and anatomical organization of cardiovascular pressor and depressor sites in the lateral hypothalamic area: I. descending projections
Authors: Allen Gary V. , Cechetto David F.
Published: January 2005

The present study describes the anatomical organization of projections from functionally defined cell groups of the lateral hypothalamic area. Cardiovascular pressor and depressor sites were identified following microinjection (5–50 nl) of 0.01–1.0 M L‐glutamate or D, L‐homocysteate into the anesthetized rat. Subsequent injections of Phaseolus vulgaris‐leucoagglutinin (PHA‐L) or wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP) were made into pressor or depressor sites and their connections with the brainstem and spinal cord were traced.

Decreases in blood pressure (10–45 mmHg) and heart rate (20–70 bpm) were elicited from tuberal (LHAt) and posterior (LHAp) regions of the lateral hypothalamic area (LHA). Depressor neurons in the LHAt have descending projections to the central gray, dorsal and median raphe nuclei, pedunculopontine tegmental nucleus, pontine reticular formation, medial and lateral parabrachial nuclei, laterodorsal tegmental region, and medullary reticular formation including the region of the lateral tegmental field, nucleus ambiguus, and rostrocaudal ventral lateral medulla. In contrast, descending projections from depressor neurons in the LHAp have dense terminal fields in the rostral, middle, and commissural portions of the nucleus of the solitary tract and the lateral tegmental field as well as the ventrolateral central gray, pedunculopontine tegmental nucleus, and medial and lateral parabrachial nuclei. Both the LHAt and LHAp have light projections to the intermediate region of the cervical and thoracic spinal cord.

Increases in blood pressure (10–40 mmHg) and heart rate (20–70 bpm) were elicited almost exclusively from neurons located medial to the LHAt and LHAp in a region surrounding the fornix, termed the perifornical area (PFA). Pressor cells in the PFA have descending projections to the central gray, dorsal and median raphe nuclei, laterodorsal tegmental nucleus, and Barrington's nucleus as well as a light projection to the commissural portion of the nucleus of the solitary tract and the intermediate region of the cervical and thoracic spinal cord. The retrograde labeling observed in the WGA‐HRP studies indicates that cells in most terminal fields have reciprocal projections to the pressor and depressor regions of the LHA. The results demonstrate that groups of neurons in the lateral hypothalamus with specific cardiovascular function have differential projections to the brain stem.
Converging GABA‐ and glutamate‐immunoreactive axons make synaptic contact with identified hypothalamic neurosecretory neurons
Authors: Decavel Chantal , van den Pol Anthony N.
Published: January 2005

To study the neurochemical identity of axons in synaptic contact with identified hypothalamic neurosecretory neurons in rats, we combined retrograde axonal transport of a marker molecule with postembedding immunogold staining for ammo acid neurotransmitters. After intravenous injections of horseradish peroxidase, neurosecretory neurons with axons in the median eminence or neurohypophysis transported the peroxidase retrogradely back to the cell body of origin. Serial ultrathin sections from the paraventricular and arcuate nuclei were immunostained with glutamate or GABA antisera. Peroxidase‐labeled neurons and their dendrites received synaptic contact from colloidal gold‐labeled axons immunoreactive for GABA or for glutamate. Axons which were highly immunoreactive for GABA and other axons immunoreactive for glutamate but not for GABA consistently made converging synaptic contact with the same peroxidase‐labeled cell. Some of the peroxidase‐labeled neurons from the arcuate nucleus which were postsynaptic to both GABA and glutamate axons were themselves identified as being GABA immunoreactive. Serial ultrathin sections revealed that multiple presynaptic axons immunoreactive for glutamate or GABA made repeated contacts with single neurons. These results suggest a widespread convergence of the major inhibitory and excitatory amino acid transmitter on the neurons which control both the anterior and posterior pituitary hormones.
Localization of corticotropin‐releasing factor‐like immunoreactivity in monkey olfactory bulb and secondary olfactory areas
Authors: Bassett J. L. , Shipley M. T. , Foote S. L.
Published: January 2005

Electrophysiological and anatomical observations suggest that terminals of olfactory bulb mitral cells ending in rat primary olfactory cortex exert certain postsynaptic effects via an excitatory amino acid neurotransmitter. Recent anatomical studies have shown that several peptides, most notably corticotropin‐releasing factor (CRF) (Imaki et al., '89) (Brain Res., 496:35–44), are also localized within rat olfactory bulb projection neurons, thus raising the possibility that there is a peptide cotransmitter in this system. In contrast to the availability of data for rodents, very little is known about the distribution of peptides and other putative transmitters in the olfactory systems of primate species. In the present study, sections through the olfactory bulb and its target areas were obtained from two monkey species (Saimiri sciureus and Macaca fascicularis) and processed for immunohistochemistry with a well‐characterized polyclonal antiserum directed against the human form of CRF. Virtually identical results were obtained in the two species. Within the olfactory bulb, nearly all mitral and many tufted cells contained CRF‐like immunoreactivity. CRF‐positive fibers were seen within the olfactory tract and olfactory stria, which contain the axons of mitral and tufted cells. Within the anterior olfactory nucleus and layer Ia of the olfactory tubercle and piriform cortex, immunoreactivity was seen within fine processes, as well as in coarse, varicose fibers and isolated puncta. CRF‐positive cells were seen within layer III of the olfactory tubercle and piriform cortex. Immunoreactive fibers and varicosities were also seen within olfactory‐recipient regions of the amygdala and entorhinal cortex. These observations suggest that CRF may act as a transmitter and/or neuromodulator in primate olfactory system.
Age‐related changes in capsaicin‐induced degeneration in rat brain
Authors: Ritter Sue , Dinh Thu T.
Published: January 2005

Previous results indicate that the pattern of capsaicin‐induced degeneration in the rat central nervous system is age‐related. Experiments utilizing capsaicin's selective neurodegenerative effects to study the function of central neural circuits will therefore require a detailed understanding of capsaicin's central neurotoxicity in rats of different ages. The goal of this experiment was to characterize the degeneration induced in the rat brain by systemic treatment with capsaicin at different ages (10, 15, 20, 25, 30 or 75 days, or 11 months), using a cupric silver stain to label degenerating neurons. Results revealed degenerating cell bodies in the ventromedial brainstem in capsaicin‐treated rats of all age groups, though they were more numerous in adult rats than in pups. In addition, many areas contained capsaicin‐induced nerve terminal degeneration both in rat pups and in adult rats. These areas were the substantia gelatinosa of the spinal cord dorsal horn; the solitary tract; the nucleus of the solitary tract, visceral portion; the area postrema; the trigeminal nerve and spinal trigeminal nucleus; the medial nucleus of the inferior olive; the rostral, dorsomedial and dorsolateral interpeduncular subnuclei and overlying interfascicular nucleus; the supramammillary area; the lateral septal nucleus; the bed nucleus of the stria terminalis, anterior medial portion; the optic nerve and tract; the suprachiasmatic nucleus, ventroposterolateral portion; the magnocellular subnucleus of the ventrolateral geniculate nucleus; the intergeniculate leaf; the medial pretectal nucleus and the olivary pretectal nucleus. In several, but not all of these areas, the apparent density of degenerating terminals was significantly less in adult rats than in pups. In other brain sites, capsaicin‐induced degeneration was observed only in rats younger than 30 days of age. These areas were the lateral habenula, medial part; the sphenoid nucleus; and the stria medullaris. Still other brain sites lost their sensitivity to capsaicin sometime between 30 and 75 days of age. These areas were the bed nucleus of the stria terminalis, medial posteromedial part; the medial preoptic nucleus, central part; the septohypothalamic nucleus; the ventral reuniens area; and the ventromedial hypothalamic nucleus. Adult rats 75 days and 11 months of age did not differ detectably in their response to capsaicin. Thus, loss or attenuation of capsaicin sensitivity is not progressive; throughout life. It does not occur in all capsaicin‐sensitive sites. Where it does occur, loss of sensitivity occurs prior to adulthood and follows a distinct and reproducible time course that may differ for different sites.
Immunohistochemical organization of the ventral lateral geniculate nucleus in the ground squirrel
Authors: Agarwala Seema , May Jack G. , Moore Jean K. , Petry Heywood M.
Published: January 2005

The ventral lateral geniculate nucleus (vLGN) of the thirteen‐lined ground squirrel (Citellus tridecemlineatus) is a highly differentiated nucleus that is divisible into five major subdivisions on the basis of retinal projections and cytoarchitecture. To pursue the likelihood that these subdivisions (the dorsal cap, intergeniculate leaflet, external magnocellular lamina, internal magnocellular lamina, and parvicellular segment) correlate with the functional diversity of this complex, the present study examined the neurochemical composition of the vLGN with regard to substances that have previously proved useful in distinguishing functionally distinct subregions within nuclei (i.e., neuropeptide Y (NPY), substance P (SP), leucine and methionine enkephalins, gamma‐aminobutyric acid (GABA), cytochrome oxidase (CO), acetylcholinesterase (AChE), and NADPH‐diaphorase).

The results showed a clear differential neurochemical distribution within the nucleus. Neuropeptide Y immunoreactive perikarya were found predominantly in the intergeniculate leaflet and external magnocellular lamina, with only a few present in the internal magnocellular lamina and dorsal cap, and none observed in the parvicellular segment. NPY+ fibers, however, were present in all divisions except the parvicellular segment. The highest concentration of SP immunoreactive cells was observed in the internal magnocellular lamina, and substantial numbers also were scattered in the external magnocellular lamina and parvicellular segment. SP+ fibers were seen predominantly in the intergeniculate leaflet and the magnocellular laminae. The heaviest concentration of enkephalinergic fibers occurred in the internal magnocellular lamina and dorsal cap, but fibers were also observed in the external magnocellular lamina and intergeniculate leaflet. GABA reactivity was widespread throughout the vLGN, with the dorsal cap and external magnocellular lamina most heavily labeled, followed by the intergeniculate leaflet and the internal magnocellular lamina. Cytochrome oxidase, AChE, and NADPH‐diaphorase histochemistry revealed rich reactivity within the dorsal cap, and external and internal magnocellular laminae and paler reactivity in the intergeniculate leaflet and parvicellular segment. The external magnocellular lamina was more reactive for CO and NADPH‐diaphorase than AChE, while the internal magnocellular lamina showed the opposite pattern of reactivity. In addition, NADPH‐diaphorase reactive cells were present in caudal intergeniculate leaflet and lateral external magnocellular lamina.

These local differences in the neurochemical character of the vLGN support its parcellation into multiple subdivisions. Taken in conjunction with the differences in cytoarchitecture and retinal projections, these results suggest substantial function diversity within the ventral lateral geniculate complex.
Antennular projections to the midbrain of the spiny lobster. I. Sensory innervation of the lateral and medial antennular neuropils
Authors: Schmidt Manfred , Van Ekeris Leslie , Ache Barry W.
Published: January 2005

The organization of sensory afferents in the antennular nerve (AN) of the spiny lobster and the central arborization of the afferents in the lateral and medial antennular neuropils (LAN, MAN) were analyzed by backfilling the AN with biocytin. The MAN receives primarily thick afferents (diameter ≥ 10 μm) with a consistent pattern of arborization from the medial of the three major divisions of the AN. The LAN, in contrast, receives many thin to medium‐sized afferents (diameter ≤ 0.3–5 μm), in addition some with diameters ≥ 5 μm, from the lateral and dorsal divisions of the AN. In contrast to the consistent pattern of arborization in the MAN, afferents projecting to the LAN arborize in widely different patterns. Serially arranged, orthogonal side branches that are suggestive of topographical representation of the serially arranged sensilla on the antennule contribute to the stratification of the LAN. Together with existing electrophysiological data, these morphological findings are consistent with the idea that the MAN receives primarily mechanosensory (largely statocyst) input, as previously thought, but that the LAN receives chemosensory as well as mechanosensory input. The chemosensory input to the LAN would represent a novel pathway for processing chemosensory input from the antennule.
Light and electron immunocytochemical localization of AMPA‐selective glutamate receptors in the rat brain
Authors: Petralia Ronald S. , Wenthold Robert J.
Published: January 2005

Since four AMPA‐type excitatory amino acid receptor subunits have been cloned recently, it is now possible to localize these important molecules in the nervous system. A comprehensive study of AMPA receptor immunocytochemistry was carried out on vibratome sections of rat brain, which were immunolabeled with antibodies made against peptides corresponding to the C‐terminal portions of AMPA‐receptor subunits: GluR1, GluR2/3, and GluR4. Labeling was most prominent in forebrain structures such as the olfactory bulb and tubercle, septal nuclei, amygdaloid complex, hippocampus, induseum griseum, habenula, and interpeduncular nucleus, and in the cerebellum. Different patterns of immunolabeling were evident with the antibodies to the four subunits, with marked contrast between densely and lightly stained structures with antibody to GluR1, widespread dense staining with antibody to GluR2/3, and moderate staining with antibody to GluR4. In the parietal cortex, some non‐pyramidal neurons were more densely stained than pyramidal cells with antibodies to GluR1. Neurons of the main olfactory bulb, other than granule cells, were most densely stained with antibody to GluR1. In the cerebellum, Bergmann glia were densely stained with antibodies to GluR1 and 4, while neurons, other than granule cells, were most densely stained with antibody to GluR2/3. Immunolabeling patterns of all antibodies were consistent with that of previous in situ hybridization histochemistry studies and with the overall pattern of 3H‐AMPA binding. Electron microscopy of thin sections taken from immunolabeled vibratome sections of hippocampus and cerebral cortex showed staining which was restricted mainly to postsynaptic densities and adjacent dendritoplasm, and to neuron cell body cytoplasm. We saw no convincing examples of stained presynaptic terminals, and only limited evidence of glial staining, excepting Bergmann glia.
Lateral geniculate projections to the superficial layers of visual cortex in the tree shrew
Authors: Usrey W. Martin , Muly E. Christopher , Fitzpatrick David
Published: January 2005

Our recent studies of tree shrew striate cortex have focused on the organization of lateral geniculate projections to layer IV and the projections from IV to layer III. Although these pathways play an important role in determining the response properties of layer III neurons, there are additional pathways from the lateral geniculate nucleus (LGN) that terminate directly in layer III. Previous studies provided evidence that these projections originate from layers 6 and 3 of the LGN and terminate in different subdivisions of layer III. In this study we used injections of biocytin to examine the projections of layers 6 and 3 to the cortex in more detail.

Consistent with earlier work, we found that LGN layer 6 projects heavily to lower IIIc, while LGN layer 3 terminates densely in layer IIIb and sparsely throughout layers IIIa‐I. In addition, we found that neurons in layers 6 and 3 have collateral projections: neurons in LGN layer 6 project to the bottom of layer IVb and sparsely to I–IIIb; neurons in LGN layer 3 project sparsely to layers V and VI and to the middle of IV.

These patterns of projections are significant in the light of our studies of the connections from cortical layer IV to layer III. LGN projections to the superficial layers are organized into parallel pathways that exert selective influence over different populations of neurons in layers I–III and on the layer IV neurons that supply them. © 1992 Wiley‐Liss, Inc.