Physiological and induced neuronal death are not affected in NSE-bax transgenic mice

The intracortical organization of the noradrenaline (NA) and vasoactive intestinal polypeptide (VIP) systems provides ample opportunity for functional convergence, and accumulated evidence indicates that NA and VIP share certain cellular actions upon both neuronal and nonneuronal cortical elements. In the present study, a double immunolabeling method was combined with a silver-gold intensification procedure to examine the ultrastructural relationships of the NA coeruleocortical afferents and the intrinsic VIP neurons with three main constituents of the cortex: neurons, astrocytes, and blood vessels. Electron microscopy of singly or doubly labeled material indicated that NA and VIP boutons are engaged in a variety of anatomical relationships with both neuronal and nonneuronal elements. Dendritic shafts and perikarya of nonpyramidal neurons, some of which are VIP positive, receive combined NA and VIP synapses. A significant number of cortical microvessels are in intimate contact with NA or VIP profiles. NA axons often form perivascular loops, and VIP dendritic shafts of large diameter are frequently observed to bend around the vessel circumference. Serial section examination demonstrates that some NA boutons are directly apposed to the capillary wall at sites of glial end-feet discontinuities, whereas VIP boutons contact astrocytic sleeves of capillaries but never cross the perivascular astroglial barrier. Some VIP dendrites containing coated vesicles make intimate contact with the capillary basal lamina. Astrocytic perikarya, mainly in the supragranular layers, are also directly apposed to NA and/or VIP elements. These complex anatomical relationships provide a structural basis for the known interactions between NA and VIP in the control of cortical metabolism and function.     

Area-specific laminar distribution of cortical feedback neurons projecting to cat area 17: quantitative analysis in the adult and during ontogeny

Corticocortical pathways can be classified as feedback and feedforward, in part according to the laminar distribution of the parent cell bodies. Here, we have developed exhaustive sampling procedures to determine unambiguously this laminar distribution. This shows that individual extrastriate areas in the adult cat have highly stereotyped proportions of supragranular layer neurons with respect to the total population of neurons back-projecting to area 17. During development, these adult laminar patterns emerge from an initially uniform radial distribution through a process of selective reorganization, which is highly specific to each area. Injections of fluorescent retrograde tracers were made in area 17. In areas 19, 20, posteromedial lateral suprasylvian area, and anteromedial lateral suprasylvian area, we defined a projection zone as the region containing retrogradely labeled neurons. In the neonate, counts of labeled neurons throughout the projection zones show constant percentages of 40% in the supragranular layers. During development, there is an area-specific reduction in the percentage of supragranular labeled neurons generating the laminar distributions characteristic of each area. Numbers of labeled neurons were estimated at different eccentricities of the projection zone. This finding indicates that during development there is a relative decrease in the numbers of labeled neurons of the periphery of the projection zone in the supragranular layers but not in the infragranular layers. This decrease is accompanied by a relative decrease in the dimensions of the supragranular projection zone with respect to the infragranular projection zone. These findings suggest that each extrastriate area precisely adjusts the proportions of supragranular layer neurons back-projecting to striate cortex in part by developmental changes in the divergence-convergence values of individual neurons. This shaping of corticocortical connectivity occurs relatively late in postnatal development and could, therefore, be under epigenetic control.     

Laminar differences in bicuculline methiodide's effects on cortical neurons in the rat whisker/barrel system

Extracellular unit recordings were made at various depths within SmI barrel cortex of immobilized, sedated rats, in the presence and absence of titrated amounts of the GABA(A) receptor antagonist bicuculline methiodide (BMI). Principal and adjacent whiskers were moved singly, or in paired combination in a condition-test paradigm, to assess excitatory and inhibitory receptive field (RF) characteristics. Neurons were classified as regular- or fast-spike units, and divided into three laminar groups: supragranular, granular (barrel), and infragranular. BMI increased response magnitude and duration, but did not affect response latencies. The excitatory RFs of barrel units, which are the most tightly focused on the principal whisker, were the most greatly defocused by BMI; infragranular units were least affected. All three layers had approximately equal amounts of adjacent whisker-evoked, surround inhibition, but BMI counteracted this inhibition substantially in barrel units and less so in infragranular units. The effects of BMI were most consistent in the barrel; more heterogeneity was found in the non-granular layers. These lamina-dependent effects of BMI are consistent with the idea that between-whisker inhibition is generated mostly within individual layer IV barrels as a result of the rapid engagement of strong, local inhibitory circuitry, and is subsequently embedded in layer IV's output to non-layer IV neurons. The latter's surround inhibition is thus relatively resistant to antagonism by locally applied BMI. The greater heterogeneity of non-granular units in terms of RF properties and the effects of BMI is consistent with other findings demonstrating that neighboring neurons in these layers may participate in different local circuits.     

Intrinsic inhibitory pathways in mouse barrel cortex

The organization of intrinsic connections in the mouse somatosensory cortex was studied by combining tract-tracing and immunocytochemical techniques. Injections of HRP or fluorescent beads were made into the supragranular or infragranular layers of the posteriomedial barrel subfield. Numerous cells were retrogradely labeled within a vertical column centered on each injection site. Retrogradely labeled cells were also found > 3 mm horizontal to the injection. Dual-label immunocytochemistry identified the population of inhibitory, GABAergic cells forming intrinsic horizontal connections. Double-labeled cells were found predominantly within a 200 microns radius horizontal to an injection site. These findings indicate that intrinsic inhibitory pathways in the barrel cortex do not provide a substrate for direct GABAergic interactions among barrel columns, and that inter-columnar interactions are primarily excitatory.     

Induction, identification or folie à deux? Psychodynamics and genesis of Munchausen syndromes by proxy and false allegations of sexual abuse in adolescents

The substantia nigra (SN) has long been known as an important source of afferents to the pedunculopontine tegmental nucleus (PPN). However, it has not been established which of the chemospecific cell populations receive this synaptic input. We sought to address this issue by a correlative light and electron microscopic approach that combines anterograde tracing of nigral efferents with pre-embedding choline acetyltransferase (ChAT) and/or glutamate (Glu) immunohistochemistry. Following large bilateral injections of Phaseolus vulgaris-leucoagglutinin (PHA-L) in the SN, the labeled nigrotegmental fibers were concentrated in a small area of the mesopontine tegmentum which contained very few ChAT-immunoreactive (ChAT-ir) cell bodies. However, strands of fine varicose fibers penetrated to adjacent regions of the PPN which harbored numerous cholinergic perikarya. The anterogradely labeled boutons were often seen in the proximity of ChAT-ir perikarya and dendrites, but the majority (82-93%) established symmetric synaptic junctions with noncholinergic profiles. In the pars dissipata of the PPN (PPNd), one-third of the labeled terminals synapsed onto noncholinergic perikarya and primary dendrites, while in the pars compacta of the PPN (PPNc) axosomatic synapses were rare. The possibility that the perikarya receiving a rich synaptic input from the SN are glutamatergic was tested in experiments combining anterograde transport of biotinylated tracers biocytin and dextran-amine (BDA) with glutamate immunohistochemistry. In double-labeled sections, Glu-ir perikarya within the terminal plexus of nigrotegmental fibers were surrounded by synaptic terminals. The PPNd also contained retrogradely BDA-labeled neurons which were contacted by anterogradely labeled terminals. These results indicate that although a small subpopulation of cholinergic neurons in the mesopontine tegmentum receive direct synaptic input from the SN, the primary target of nigrotegmental fibers are glutamatergic cells in the PPNd. Our results also provide ultrastructural evidence that some nigrotegmental fibers innervate pedunculonigral neurons.     

Visual latencies in areas V1 and V2 of the macaque monkey

Latencies to small flashing spots of light were measured in different layers of areas V1 and V2 in anesthetized and paralyzed macaque monkeys. The shortest latencies were found in layers 4C alpha and 4B of area V1. Latencies in layer 4C beta were on average 20 ms longer than those in 4C alpha and 4B. The shortest latencies in area V2 were observed in the infragranular layers and they did not differ significantly from those found in the infragranular layers in V1. Similarly, latencies in the supragranular layers of V2 were not significantly different from those measured in the supragranular layers of V1. These results show that, in area V1, neurons of the magnocellular pathway are activated on average 20 ms earlier than those of the parvocellular pathway. Our data also suggest that much processing begins simultaneously in areas V1 and V2.     

A prospective study of the usefulness of clinical and laboratory parameters for predicting percentage of dehydration in children

The lateral geniculate nucleus of the rat was injected with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) to see if geniculo-cortical axons terminate on vasoactive intestinal polypeptide immunoreactive (VIP-IR) neurons of the primary visual cortex. PHA-L-labelled boutons attached to VIP-IR perikarya and dendrites were identified as presynaptic parts of asymmetrical synapses. This geniculo-cortical projection to VIP-IR cells in the visual cortex and comparable findings in the somatosensory cortex suggest that sensory input from specific thalamic nuclei may influence local circuit inhibition and the metabolic state within the cortical domain via VIP-IR neurons.     

Zinc-positive afferents to the rat septum originate from distinct subpopulations of zinc-containing neurons in the hippocampal areas and layers. A combined fluoro-gold tracing and histochemical study

The purpose of the present study was to examine whether zinc-positive and zinc-negative hippocampal neurons in rats differed with respect to their projections to the septum. By combining retrograde axonal transport of the fluorescent tracer Fluoro-Gold with histochemical demonstration of zinc selenide complexes in zinc-containing neurons after intraperitoneal injection of sodium selenite, we were able to visualize the distribution of retrogradely Fluoro-Gold labeled neurons and zinc-containing neurons in the same sections. After unilateral injection of Fluoro-Gold into the rat septum a few retrogradely labeled cells were observed in layer IV of the ipsilateral medial entorhinal area, and numerous labeled cells were observed mainly in the superficial layers of the ipsilateral subicular areas and throughout the CA1 and CA3 pyramidal cell layers, as well as in the contralateral CA3 pyramidal cell layer. Zinc-containing neurons were observed in layers IV-VI of the medial entorhinal area, layers II and III of the parasubiculum, layers II, III and V of presubiculum, and in the superficial CA1 and deep CA3 pyramidal cell layers. Cells double-labeled with Fluoro-Gold and zinc selenide complexes were primarily located in distal (relative to the area dentata) parts of the superficial CA1 pyramidal cell layer and distal parts of the deep CA3 pyramidal cell layer and in layers II and III of presubiculum. Only a very few double-labeled cells were seen in the contralateral CA3. The result demonstrates that the hippocampo-septal projection of rats is a mixture of zinc-positive and zinc-negative fibers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Postnatal development of calcium-binding proteins calbindin and parvalbumin in human visual cortex

In adult primate visual cortex, the calcium-binding proteins calbindin (CB) and parvalbumin (PV) are localized in different subsets of GABAergic neurons with a characteristic laminar distribution. However, the emergence and development of CB and PV in relation to the periods of functional maturation of the human visual cortex are not known. Therefore, we examined (i) postnatal changes in the distribution of immunoreactivity (ir) for CB and PV in the visual cortex; (ii) the pattern of changes in immunoreactivity in relation to the synaptic maturation; and (iii) differences in the maturation of CB and PV immunoreactivity between areas 17 and 18. We found a consistently high expression of CB in neonatal visual cortex, particularly in layer IV and infragranular layers. However, despite an early appearance of PV, its peak in development occurred only after 2 months of age, characterized by a transient overexpression in the thalamo-recipient layer IV and a continuous inside-out maturation in supragranular layers. The neonatal pattern of high CB-ir in layers IV-VI was transformed during infancy and childhood into an adult pattern of high CB-ir in layer II, but low CB-ir in layer IV and infragranular layers. There was no difference in pattern and tempo of maturation of calcium-binding proteins between area 17 and 18, indicating simultaneous development of cortical inhibitory circuits among cytoarchitectonically and functionally distinct cortical areas. In addition, the reorganization of CB/PV expression temporally and spatially coincides with the course of cortical synaptogenesis, and delineates the major stages of maturation of the human visual cortex.     

Growth of callosal terminal arbors in primary visual areas of the cat

In kittens ranging in age between postnatal day (P) 5 and P150, callosal axons originating near the 17/18 border were anterogradely labelled with biocytin and reconstructed from serial sections. At the end of the first postnatal week most of the axons begin to invade the cortex near the 17/18 border with multiple branches; some axons already span the grey matter up to layer 1. Branches tend to grow into the grey matter in loose bundles 相似文献   

Projections from the presubiculum and the parasubiculum to morphologically characterized entorhinal-hippocampal projection neurons in the rat

The relations between the inputs from the presubiculum and the parasubiculum and the cells in the entorhinal cortex that give rise to the perforant pathway have been studied in the rat at the light microscopical level. Projections from the presubiculum and the parasubiculum were labeled anterogradely, and, in the same animal, cells in the entorhinal cortex that project to the hippocampal formation were labeled by retrograde tracing and subsequent intracellular filling with Lucifer Yellow. The distribution and the number of appositions between the afferent fibers and hippocampal-projection neurons in the various layers of the entorhinal cortex were analyzed. The results show that layers I-IV of the entorhinal cortex contain neurons that give rise to projections to the hippocampal formation. The morphology of these projection neurons is highly variable and afferents from the presubiculum and the parasubiculum do not show a preference for any specific morphological cell type. Both inputs preferentially innervate the dendrites of their target cells. However, presubicular and parasubicular projections differ with respect to the layer of entorhinal cortex they project to. The number of appositions of presubicular afferents with cells that have their cell bodies in layer III of the entorhinal cortex is 2-3 times higher than with cells in layer II. In contrast, afferents from the parasubiculum form at least 2-3 times as many synapses on the dendrites of cells located in layer II than on neurons that have their cell bodies in layer III. Cells in layers I and IV of the entorhinal cortex receive weak inputs from the presubiculum and parasubiculum. Not only is the presubiculum different from the parasubiculum with respect to the distribution of projections to the entorhinal cortex, they also differ in their afferent and efferent connections. In turn, cells in layer II of the entorhinal cortex differ in their electrophysiological characteristics from those in layer III. Moreover, layer II neurons give rise to the projections to the dentate gyrus and field CA3/CA2 of the hippocampus proper, and cells in layer III project to field CA1 and the subiculum. Therefore, we propose that the interactions of the entorhinal-hippocampal network with the presubiculum are different from those with the parasubiculum.     

Neurons and synaptic patterns in the deep layers of the superior colliculus of the cat. A Golgi and electron microscopic study

Golgi and electron microscopic observations were made on the neurons in the deep layers (below the stratum opticum) of the cat superior colliculus. Large neurons, 35-60 micrometers in somal diameter, occur mainly in the lateral two-thirds of the colliculus. They have numerous somatic and dendritic spines and receive a large number of axon terminals (bouton covering ratio: more than 70%). The medium-sized neurons (20-30 micrometer), with a moderate number of dendritic spines, show a lower bouton covering ratio (25-30%). The ratio for small neurons (8-15 micrometers), with very few dendritic spines, is less than 10%. The medium-sized and small neurons are distributed throughout the colliculus and show marked variability in the dendritic arrangement. Seven different types of axon terminals were distinguished: types I, II, V, and VII form asymmetrical and types III, IV, and VI symmetrical synapses. Type I terminals represent small boutons containing predominantly spherical vesicles, and are in contact mainly with small dendritic profiles. Type II terminals are medium-sized and slender, contain a mixture of spherical and slightly oval vesicles, and make synaptic contacts with small to medium-sized dendrites and somatic spines. This type of terminal is occasionally presynaptic to vesicle-containing dendrites (type VIII). Type III terminals are small, contain flattened vesicles predominantly, and are presynaptic to a wide variety of neuronal elements in the deep layers of the superior colliculus. Type IV terminals are represented by medium to large-sized boutons that contain pleomorphic vesicles and make synaptic contacts chiefly with the large neurons. Type V and VI terminals exhibit a quite dense axoplasmic matrix and mainly contact the large neurons. Type VII terminals are often in the form of boutons en passant and contain numerous large granular vesicles. Pleomorphic vesicle-containing dendrites (type VIII terminals) are also observed to participate in the axodendrodendritic serial synapses.     

Colocalization of NADPH-diaphorase staining and VIP immunoreactivity in neurons in opossum internal anal sphincter

Nitric oxide and vasoactive intestinal polypeptide (VIP) are important inhibitory neurotransmitters mediating relaxation of the internal anal sphincter. The location and coexistence of these two neurotransmitters in the internal anal sphincter has not been examined. We performed a double-labeling study to examine the coexistence of nitric oxide synthase and VIP in the opossum internal anal sphincter using the NADPH-diaphorase technique which is a histochemical stain for nitric oxide synthase. In perfusion-fixed, frozen-sectioned tissue, VIP-immunoreactive neurons were labeled using immunofluorescence histochemistry. After photographing the VIP-immunoreactive neurons, nitric oxide synthase was labeled using the NADPH-diaphorase technique. Ganglia containing neuronal cell bodies were present in the myenteric plexus for the entire extent of the internal anal sphincter. VIP-immunoreactive and NADPH-diaphorase-positive neurons were present in ganglia in the myenteric as well as the submucosal plexuses. Most of the VIP-immunoreactive neurons were also NADPH-diaphorase positive. VIP and nitric oxide synthase are present and frequently coexist in neurons in the internal anal sphincter of the opossum. These neurons may be an important source of inhibitory innervation mediating the rectoanal reflex-induced relaxation of the sphincter. The demonstration of the coexistence of these two neurotransmitters will be of fundamental importance in unraveling their relationship and interaction in the internal anal sphincter as well as other systems.     

Cat intraamygdaloid inhibitory network: ultrastructural organization of parvalbumin-immunoreactive elements

Projection neurons of the basolateral (BL) amygdaloid complex are regulated by an intrinsic inhibitory network. To improve our understanding of this inhibitory circuit, we studied the synaptology of parvalbumin-immunopositive (PV+) elements as this calcium-binding protein is localized in a subpopulation of gamma-aminobutyric acid (GABA)-ergic interneurons. Two populations of PV+ cells were identified on the basis of soma shape (ovoid, type A vs. polygonal, type B). In the lateral and BL nuclei, the majority of boutons in contact with PV+ cells formed asymmetric synapses (types 1-3; 94%), whereas a minority (type 4, 6%) established symmetric synaptic contacts and resembled GABAergic terminals. In both nuclei, type B PV+ perikarya were more densely innervated than were type A neurons. However, the pattern of synaptic innervation of type B PV+ neurons differed in the two nuclei: in the lateral nucleus, they were almost exclusively innervated by a population of small, presumed excitatory terminals (type 1), whereas the four categories of terminals contributed more equally to their innervation in the BL nucleus. PV+ boutons belonged to a single category of terminals that was enriched with GABA and formed symmetric synapses mostly with the proximal part of PV neurons. The proportion of axosomatic synapses was significantly higher in the lateral nucleus than in the BL nucleus (33% vs. 18%). The reverse was true for the contacts with proximal dendrites (33% in the lateral nucleus vs. 46% in the BL nucleus). The remaining terminals formed synapses with distal dendrites (23-28%) and spines (8-12%). These results indicate that PV+ interneurons receive massive excitatory inputs and that PV+ terminals are strategically located to exert a powerful inhibitory control of amygdala neurons.     

Pallidal afferent territory of the Macaca mulatta thalamus: neuronal and synaptic organization of the VAdc

Ventral anterior thalamic nucleus pars densicellularis (VAdc) as delineated earlier (Ilinsky and Kultas-Ilinsky [1987] J. Comp. Neurol. 262:331-364) was analyzed by using qualitative and quantitative neuroanatomical techniques. Projection neurons (PN), retrogradely labeled with wheat germ agglutinin conjugated horseradish peroxidase from the cortex, were small to medium in size (mean area, 312 microm2) with numerous primary dendrites displaying a tufted branching pattern. Local circuit neurons (LCN), immunoreactive for gamma-aminobutyric acid (GABA) and glutamic acid decarboxylase, were small (mean area, 110 microm2), and gave off few dendrites. Two subpopulations of GABA positive boutons (F1 type) were distinguished: large (mean area, 2.6 microm2) terminals with symmetric synapses containing few pleomorphic vesicles and numerous mitochondria densely covered proximal PN sites; smaller F1 boutons with a slightly different morphology contacted mostly distal PN dendrites. Two subpopulations of terminals containing round vesicles and forming asymmetric synapses were distinguished by bouton size (mean areas, 0.4 microm2 and 1.6 microm2, respectively). These targeted mainly distal PN dendrites, but some synapsed proximally next to large F1 boutons. On distal dendrites, representatives of both types were labeled from the cortex. The density of boutons with symmetric and asymmetric synapses (the number of boutons per 100 microm of PN membrane length) was 3.3:0.2 on primary, 2.5:1.2 on secondary, and 0.8:12 on distal dendrites. The numerical density of synapses formed by presynaptic LCN dendrites on all PN levels was 20 to 40 times less than that of axon terminals at the same sites. Afferent input to LCN from boutons of all types, including that from 50% of labeled cortical boutons, mainly targeted distal dendrites. Overall, the findings suggest that PN in VAdc receive massive inhibitory input proximally intermingled with some presumably excitatory input, and that LCN contribution to PN inhibition is modest.     

Contributions of individual layer 2-5 spiny neurons to local circuits in macaque primary visual cortex

We studied excitatory local circuits in the macaque primary visual cortex (VI) to investigate their relationships to the magnocellular (M) and parvocellular (P) streams. Sixty-two intracellularly labeled spiny neurons in layers 2-5 were analyzed. We made detailed observations of the laminar and columnar specificity of axonal arbors and noted correlations with dendritic arbors. We find evidence for considerable mixing of M and P streams by the local circuitry in VI. Such mixing is provided by neurons in the primary geniculate recipient layer 4C, as well as by neurons in both the supragranular and infragranular layers. We were also interested in possible differences in the axonal projections of neurons with different dendritic morphologies. We found that layer 4B spiny stellate and pyramidal neurons have similar axonal arbors. However, we identified two types of layer 5 pyramidal neuron. The majority have a conventional pyramidal dendritic morphology, a dense axonal arbor in layers 2.4B, and do not project to the white matter. Layer 5 projection neurons have an unusual "backbranching" dendritic morphology (apical dendritic branches arc downward rather than upward) and weak or no axonal arborization in layers 2-4B, but have long horizontal axonal projections in layer 5B. We find no strong projection from layer 5 pyramidal neurons to layer 6. In macaque V1 there appears to be no single source of strong local input to layer 6; only a minority of cells in layers 2-5 have axonal branches in layer 6 and these are sparse. Our results suggest that local circuits in V1 mediate interactions between M and P input that are complex and not easily incorporated into a simple framework.     

Patchy and laminar terminations of medial geniculate axons in monkey auditory cortex

The object of this study was to identify the terminal distributions of thalamocortical axons arising in chemically characterized subdivisions of the medial geniculate complex. Large injections of wheat germ agglutinin-conjugated horseradish peroxidase or small injections of Phaseolus vulgaris leucoagglutinin were made in the medial geniculate complex of Macaca fuscata. The terminal distributions of labeled axons in the cortex were correlated with auditory cortical fields demonstrable by different intensities of immunoreactivity for parvalbumin. Fibers from the ventral nucleus terminated mainly in layer IV and deep portion of layer III (IIIB), with additional terminations in layers I-IIIA and in layer VI. In layers IIIB-IV, a major terminal plexus was formed by a small number of dense patches, 300-500 microns in diameter, surrounded by smaller satellite patches. The patches conformed to a similarly lobulated pattern of parvalbumin fiber immunoreactivity. Terminations of some individually labeled thalamocortical fibers were restricted to a single patch, whereas others innervated more than one patch by collateral branches. Fibers from the dorsal nuclei ending in areas of less dense parvalbumin immunoreactivity surrounding the primary auditory cortex formed much larger terminal patches centered largely in layer IIIB. Fibers from the magnocellular nucleus had relatively few terminal branches but innervated extremely wide areas by collaterals of single axons. Two types of axons arose from the magnocellular nucleus, one terminating preferentially in middle cortical layers and the other exclusively in layer I. These may arise respectively from parvalbumin- and calbindin-immunoreactive cell populations in the magnocellular nucleus.     

Immunocytochemical localization of vasoactive intestinal peptide and neuropeptide Y in the bovine ovary

The distribution of the neuropeptides vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) was studied immunocytochemically in bovine ovaries from 3 mo of gestation up to and including puberty, and from adult cows at three stages of the estrous cycle. The appearance of VIP and NPY immunoreactivity of 4.5-6 mo of gestation coincided with the onset of follicular development. In contrast to NPY, VIP was first found in the cortex. Both VIP and NPY immunoreactivity increased with age. From 9 mo of gestation onwards, VIP and NPY were found around blood vessels and non-vascular smooth muscle cells, in the stroma near preantral follicles, and in the theca externa of antral follicles. In addition, VIP-positive cells were observed exclusively in the granulosa layer of the preovulatory follicle at the time of the LH surge. The distribution of VIP- and NPY-immunoreactive fibers in the ovary may point to an effect of these neuropeptides on various physiological processes, including follicle development and ovarian blood flow. In addition, the presence of VIP-positive cells in the granulosa layer of the preovulatory follicle is indicative of a role for VIP in ovulation.     

Synaptic and axonal remodeling of mossy fibers in the hilus and supragranular region of the dentate gyrus in kainate-treated rats

Seizures evoked by kainic acid and a variety of experimental methods induce sprouting of the mossy fiber pathway in the dentate gyrus. In this study, the morphological features and spatial distribution of sprouted mossy fiber axons in the dorsal dentate gyrus of kainate-treated rats were directly shown in granule cells filled in vitro with biocytin and in vivo with the anterograde lectin tracer Phaseolus vulgaris leucoagglutinin (PHAL). Sprouted axon collaterals of biocytin-filled granule cells projected from the hilus of the dentate gyrus into the supragranular layer in both transverse and longitudinal directions in kainate-treated rats but were not observed in normal rats. The sprouted axon collaterals projected into the supragranular region for 600-700 microm along the septotemporal axis. Collaterals from granule cells in the infrapyramidal blade crossed the hilus and sprouted into the supragranular layer of the suprapyramidal blade. Sprouted axon segments in the supragranular layer had more terminal boutons per unit length than the axon segments in the hilus of both normal and kainate-treated rats but did not form giant boutons, which are characteristic of mossy fiber axons in the hilus and CA3. Mossy fiber axons in the hilus of kainate-treated rats had more small terminal boutons, fewer giant boutons, and there was a trend toward greater axon length compared with mossy fibers in the hilus of normal rats. With the additional length of supragranular sprouted collaterals, there was an overall increase in the length of mossy fiber axons in kainate-treated rats. The synaptic and axonal remodeling of the mossy fiber pathway could alter the functional properties of hippocampal circuitry by altering synaptic connectivity in local circuits within the hilus of the dentate gyrus and by increasing the divergence of the mossy fiber terminal field along the septotemporal axis.     

The development of parvalbumin and calbindin-D28k immunoreactive interneurons in kitten visual cortical areas

Calbindin-D and parvalbumin are calcium binding proteins which are found in non-overlapping subpopulations of GABA-ergic interneurons in mammalian neocortex. We studied the development of these calcium-binding proteins in interneurons of cat striate and extrastriate cortical areas which have differing patterns of connectivity and follow different developmental timetables. We examined primary visual areas 17 and 18, secondary visual area 19, medial lateral suprasylvian and lateral suprasylvian areas (MLS and LLS) and association areas 7 and the splenial visual area from the day of birth (P0) through P101. Parvalbumin-immunoreactive (ir) interneurons followed the inside-out pattern of maturation of cortical laminae. They were located only in infragranular layers at the earliest ages and were not observed in the overlying cortical plate. At 3 weeks of age, when cortical lamination is mature, parvalbumin stained cells were found in all cortical layers except layer I. The number of stained secondary and tertiary dendrites in the parvalbumin-ir interneuronal population decreased with age. This change was associated with a shift in the molecular weight of parvalbumin detected on Western blots. During the first postnatal week, the area 17/18 border contained more parvalbumin-ir neurons than other visual areas. The developmental pattern of calbindin staining differed considerably from the parvalbumin staining pattern. Very few calbindin-ir interneurons were seen in area 17 during the first 2 weeks of life. In lateral cortical areas, calbindin-ir neurons were located in cortical plate, infragranular layers of cortex and white matter/subplate. Calbindin-ir neurons increased in supragranular layers of secondary cortical areas by P7 and in area 17 by P20. In the mature cortex, the calbindin staining pattern was bilaminar, with a dense band of calbindin-ir cells in layer II and a second band in layers V-VI. There was no difference in the distribution of calbindin-ir neurons among visual areas at maturity.