Synaptic organization and neurotransmitters in the rat accessory olfactory bulb

The accessory olfactory bulb (AOB) is the first relay station in the vomeronasal system and may play a critical role in processing pheromone signals. The AOB shows similar but less distinct lamination compared with the main olfactory bulb (MOB). In this study, synaptic organization of the AOB was analyzed in slice preparations from adult rats by using both field potential and patch-clamp recordings. Stimulation of the vomeronasal nerve (VN) evoked field potentials that showed characteristic patterns in different layers of the AOB. Current source density (CSD) analysis of the field potentials revealed spatiotemporally separated loci of inward current (sinks) that represented sequential activation of different neuronal components: VN activity (period I), synaptic excitation of mitral cell apical dendrites (period II), and activation of granule cells by mitral cell basal dendrites (period III). Stimulation of the lateral olfactory tract also evoked field potentials in the AOB, which indicated antidromic activation of the mitral cells (period I and II) followed by activation of granule cells (period III). Whole cell patch recordings from mitral and granule cells of the AOB supported that mitral cells are excited by VN terminals and subsequently activate granule cells through dendrodendritic synapses. Both CSD analysis and patch recordings provided evidence that glutamate is the neurotransmitter at the vomeronasal receptor neuron; mitral cell synapses and both NMDA and non-NMDA receptors are involved. We also demonstrated electrophysiologically that reciprocal interaction between mitral and granule cells in the AOB is through the dendrodendritic reciprocal synapses. The neurotransmitter at the mitral-to-granule synapses is glutamate and at the granule-to-mitral synapse is gamma-aminobutyric acid. The synaptic interactions among receptor cell terminals, mitral cells, and granule cells in the AOB are therefore similar to those in the MOB, suggesting that processing of chemosensory information in the AOB shares similarities with that in the MOB.     

The neuronal marker protein gene product 9.5 (PGP 9.5) is phenotypically expressed in human breast epithelium, in milk, and in benign and malignant breast tumors

The aim of this study was to examine the expression of the well-established neuronal marker protein gene product 9.5 (PGP 9.5) in nonneuroendocrine tissues of the human breast. Using antibodies directed against PGP 9.5 in an immunohistological technique, a positive staining of nerves and, surprisingly, a positive cytoplasmic reaction were obtained in normal breast epithelium, in all cases of fibroadenomata (n = 7) and in carcinoma cells in 5 out of 16 cases of breast cancers. In screening several human breast cancer cell lines, a positive immunoreaction was observed in 4 out of 6 of the cell lines. To exclude the possibility that this immunoreactivity was false, positive lysates from the same cell lines and preparations from human breast milk were subjected to NaDodSO4-polyacrylamide gel electrophoresis and Western blotting. This study confirmed the presence of PGP 9.5 in both milk and breast cancer cell lines. Because any contamination with nerve fibers can be excluded having used cell culture material or milk, it can be concluded that the presence of PGP 9.5 in the normal epithelium and in breast cancer cells is genuine. PGP 9.5 expression is, therefore, a feature of normal breast epithelia and breast cancer cells and cannot be regarded as 'neuron' specific.     

Neurocalcin immunoreactivity in the rat main olfactory bulb

The morphological characteristics and distribution of neurocalcin (NC)-immunoreactive elements were studied in the rat main olfactory bulb (OB) using a polyclonal antibody and the avidin-biotin immunoperoxidase method. NC-positive elements were abundant in the glomerular layer (GL), where numerous immunostained external tufted cells and periglomerular cells were detected. Other less abundant NC-immunolabeled populations included middle and internal tufted cells, Van Gehuchten cells, horizontal cells, vertical cells of Cajal, deep short-axon cells and granule cells. This study demonstrates the presence of NC immunoreactivity in subsets of different neuronal types in the rat main OB. This calcium-binding protein has been found in interneurons, and no evidence of immunoreactivity to NC is detected in projecting neurons. Despite the large population of labeled external tufted cells, most of them belong according to morphological criteria to the local circuit group and some others to those with interbulbar and/or intrabulbar connections. The identification of neuronal subpopulations expressing NC provides a further characterization and shows the existence of biochemical differences within morphologically identical neurons. Thus, this marker may be a useful tool in unravelling the circuitries of the rodent OB in both normal and experimental conditions. The exact physiological function of NC in the olfactory system remains unknown. On the basis of similarities to recoverin, it could be involved in mechanisms responsible for sensory adaptation. Additionally, its calcium-binding abilities may contribute to improve the temporal precision of stimuli transmission, or be concerned with general calcium-related events occurring in specific interneuronal groups.     

Calretinin- and parvalbumin-immunoreactive neurons in the rat main olfactory bulb do not express NADPH-diaphorase activity

The presence of nitric oxide synthase (NOS) in neuronal elements expressing the calcium-binding proteins calretinin (CR) and parvalbumin (PV) was studied in the rat main olfactory bulb. CR and PV were detected by using immunocytochemistry and the nitric oxide (NO) -synthesizing cells were identified by means of the reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase) direct histochemical method. The possible coexistence of NADPH-diaphorase and each calcium-binding protein marker was determined by sequential histochemical-immunohistochemical double-labeling of the same sections. Specific neuronal populations were positive for these three markers. A subpopulation of olfactory fibers and olfactory glomeruli were positive for either NADPH-diaphorase or CR. In the most superficial layers, groups of juxtaglomerular cells, superficial short-axon cells and Van Gehuchten cells demonstrated staining for all three markers. In the deep regions, abundant granule cells were NADPH-diaphorase- and CR-positive and a few were PV-immunoreactive. Scarce deep short-axon cells demonstrated either CR-, PV-, or NADPH-diaphorase staining. Among all these labeled elements, no neuron expressing CR or PV colocalized NADPH-diaphorase staining. The present data contribute to a more detailed classification of the chemically- and morphologically-defined neuronal types in the rodent olfactory bulb. The neurochemical differences support the existence of physiologically distinct groups within morphologically homogeneous populations. Each of these groups would be involved in different modulatory mechanisms of the olfactory information. In addition, the absence of CR and PV in neuronal groups displaying NADPH-diaphorase, which moreover are calmodulin-negative, indicate that the regulation of NOS activity in calmodulin-negative neurons of the rat olfactory bulb is not mediated by CR or PV.     

A quantitative assessment of innervation in the conduction system of the calf heart

BACKGROUND: The aim of the present investigation was to determine the relative distribution of autonomic and sensory nerves in the cardiac conduction tissues of calves. METHODS: A quantitative immunohistochemical and histochemical technique was adopted. RESULTS: Immunoreactivity to the general neuronal marker protein gene product 9.5 (PGP 9.5) demonstrated that all regions of the conduction system possessed a higher relative density of total nerves when compared with the surrounding myocardial tissues. Unlike myocardial innervation, the conduction system did not display an atrial-to-ventricular gradient in nerve density. PGP 9.5-immunoreactive nerve trunks and varicose nerve fibres were more numerous in the transitional atrioventricular node and the penetrating atrioventricular bundle than in either the sinus node, compact atrioventricular node, or bundle branches. The Purkinje network of the ventricular conduction tissues possessed a rich supply of PGP 9.5-immunoreactive nerve trunks and varicose nerve fibres. Acetylcholinesterase (AChE)-positive nerves were the main subtype identified in the sinus and atrioventricular nodes and in the ventricular conduction tissues, representing 50-80% of the area occupied by PGP 9.5-immunoreactive nerves. The compact atrioventricular node possessed AChE-positive and tyrosine hydroxylase (TH)-immunoreactive nerves in similar proportions (45%), although, in general, TH-immunoreactive nerves had a lower relative nerve density than AChE-positive nerves. Neuropeptide Y (NPY)-immunoreactive nerves represented the main peptide-containing subpopulation and occurred throughout the conduction system, displaying a similar pattern of distribution and relative density to those demonstrating TH immunoreactivity. Nerve fibres immunoreactive for somatostatin, vasoactive intestinal polypeptide, substance P, and calcitonin gene-related peptide formed relatively minor subpopulations. CONCLUSIONS: The general innervation of the bovine conduction tissues exhibits significant regional variation. Throughout all regions of the conduction system, AChE-positive nerve represented the dominant subtype when compared with TH- and NPY-immunoreactive nerves. The distribution and relative density of nerve subtypes in the tissues of the bovine conduction system are similar to those observed in man, whereas differences were observed in other regions, such as the atrioventricular bundle and bundle branches. This finding must be considered by those making interspecies comparisons.     

Specific detection and quantification of palmitoyl-stearoyl-phosphatidylserine in human blood using normal-phase liquid chromatography coupled with electrospray mass spectrometry

We have made an immunohistochemical study of the vomeronasal (VN) complex of 12-day-old rats to characterize the innervation of its blood vessels. The VN complex can be subdivided into rostral, middle and caudal segments, each one with a particular vascularization pattern. Several small vessels were associated with the rostral segment, whereas a large venous sinus ran along the middle and caudal segments. Immunostaining for alpha-smooth muscle actin demonstrated that the muscular sheath was asymmetric, with more cells layers in its lateral than in its medial walls. Nerves were demonstrated with antisera against protein gene product 9.5 (PGP), and against several molecules associated with specific classes of nerve fibers: the C-terminal peptide of neuropeptide Y (CPON), calcitonin gene-related peptide (CGRP), substance P (SP), galanin (GAL), vasoactive intestinal peptide (VIP) and neuronal nitric oxide synthase (NOS). The latter, was also studied with NADPH-diaphorase. Vascular associated fibers exhibited NOS-, CPON-, GAL-, CGRP-, SP- and VIP-immunoreactivity. Only the vessels of the rostral segment showed VIP-immunoreactive fibers. Each wall of the venous sinus exhibited different types of nerve fibers. CPON-, GAL-, CGRP- and SP-immunoreactive fibers concentrated in the medial wall, whereas NOS-immunoreactive ones concentrated in the lateral wall. This distribution of vascular fibers, plus the presence of sensory fibers exhibiting CGRP-, SP- and GAL-immunoreactivity within the pseudostratified epithelium of the VN tube, would be relevant to understand the operation of the pumping mechanism regulating influx and efflux from the VN tube.     

Sex difference and testosterone modulation of pheromone-induced NeuronalFos in the Ferret's main olfactory bulb and hypothalamus

A carnivore, the ferret possesses a vomeronasal organ--accessory olfactory bulb (VNO-AOB) projection to the hypothalamus; however, little is known about its function. Pheromones in soiled bedding from estrous female ferrets or an artificial peppermint odor significantly augmented nuclear Fos protein immunoreactivity (Fos-IR), a marker of neural activation, in several main olfactory bulb (MOB) sites but not in the AOB of gonadectomized male and females. Testosterone propionate (TP) significantly augmented the MOB's neuronal Fos responses to estrous females' pheromones, but not to peppermint. Estrous odors, but not peppermint, also augmented neuronal Fos-IR in the medial preoptic area (mPOA) of female, but not male, subjects. Pheromones in soiled bedding from breeding male ferrets significantly augmented neuronal Fos-IR in the MOB and in the medial amygdala of gonadectomized, TP-treated male and female subjects. Again, male pheromones failed to influence neuronal Fos-IR in the AOB of either sex, and only females showed significant increases in neuronal Fos-IR in the lateral aspect of the ventromedial nucleus and mPOA. These results point to an essential role among higher mammals of the main olfactory epithelium-MOB projection to the hypothalamus in detecting and processing pheromones. Gonadectomized ferrets showed significant increases in sniffing behavior when placed on either female or male bedding. This occurred regardless of whether they had received TP or oil vehicle, suggesting that testosterone's facilitation of neuronal Fos responses to estrous females' odors in the MOB of both sexes cannot be attributed to increased scent gathering. Androgen receptor-IR was present in the MOB granule cell layer of male and female ferrets, raising the possibility that testosterone acts directly on these cells to augment their responsiveness to pheromones.     

The distribution of novel intermediate filament proteins defines subpopulations of myenteric neurons in rat intestine

BACKGROUND/AIMS: Recent studies with neurofilament antibodies as neuronal markers have shown subpopulations of myenteric neurons that do not contain neurofilament proteins. Novel neuronal intermediate filament proteins alpha-internexin, peripherin, and nestin have been identified. The aim of this study was to examine the distribution of these novel intermediate filaments in comparison with neurofilaments in myenteric plexus neurons. METHODS: Using indirect immunofluorescence techniques in whole-mount cryostat sections from neonate and adult rat small intestine and in primary cultures of myenteric neurons, the distribution of neurofilaments, alpha-internexin, peripherin, and nestin was studied in comparison with the neuronal marker protein gene product (PGP) 9.5 in myenteric neurons. RESULTS: Sixty-five percent of neurons contained neurofilament triplet proteins. alpha-Internexin and/or peripherin were found in the neurofilament-negative neurons. PGP 9.5 was present in 80% of the myenteric neurons. Of the neurons that were PGP negative, > 95% contained peripherin or alpha-internexin. Nestin was not found in either neonate or adult myenteric neurons but was seen in glial cells in culture. CONCLUSIONS: The results suggest that a subpopulation of myenteric neurons lacks neurofilament triplet proteins but contains either peripherin, alpha-internexin, or both. This selective distribution of intermediate filaments in subpopulations of enteric neurons may support differential roles in these structurally unique neurons.     

Antibiotic and prednisolone therapy of erysipelas: a randomized, double blind, placebo-controlled study

In the early eighties we found sex differences in the vomeronasal organ (VNO) and hypothesized that the vomeronasal system (VNS), a complex neural network involved in the control of reproductive behavior, might be sexually dimorphic. At that time sex differences had already been described for some structures that receive VNO input, such as the medial amygdala, the medial preoptic area, the ventromedial hypothalamic nucleus, and the ventral region of the premammillary nucleus. Since then, we have shown sex differences in the accessory olfactory bulb (AOB), the bed nucleus of the accessory olfactory tract (BAOT), and the bed nucleus of the stria terminalis (BST). When new VNS connections were found, all of them ended in nuclei that present sex differences. In general, sex differences in the olfactory system show two morphological patterns: one in which males present greater morphological measures than females, and just the opposite. To explain the morphometric measures of males in the latter, it has been hypothesized that androgens serve as inhibitors. Our work on the involvement of the GABA(A) receptor in the development of AOB and maternal behavior sex differences also suggests that neonatal changes in neuronal membrane permeability to the ion Cl- differences. This might be the first animal model to help us to understand the situation in which human genetic and gonadal sex do not agree with brain and behavioral sex. Finally, we stress that sex differences in the VNS constitute a neurofunctional model for understanding sex differences in reproductive behaviors.     

Morphological analysis of olfactory receptor cells using whole-mount preparations of the rat nasal mucosa

The distribution and entire shape of olfactory receptor cells were investigated by means of whole-mount preparations of the nasal mucosa. Whole mucosa isolated from the nasal septum of rats was processed, as "a free-floating section", and examined by the avidin-biotin complex (ABC) method using antisera against protein gene product 9.5 (PGP 9.5) and calbindin. Essentially all receptor cells were immunolabeled with the PGP 9.5 antiserum, but only half of PGP 9.5-immunoreactive cells were calbindin-immunoreactive. In the immunostaining of whole-mount preparations, pretreatment of tissues by freeze-thawing and dipping in ethanol and xylene greatly improved the permeability of antibodies. Overview of the nasal septum showed that the dorsal and ventral portions of the rostral olfactory area extended deeply into the respiratory area, making a "semi-lunar" shape. The boundary between the two areas was clearly demarcated, although several receptor cells were scattered in the respiratory area near the boundary. Observation at higher magnification clearly demonstrated that several axons derived from perikarya gathered to form nerve bundles showing a dendritic pattern. Proximal axons close to perikarya displayed beaded structures with intense immunoreactivity. They were electron-microscopically identified as swollen portions of axons which might be formed in association with the axonal flow. The present study showed that whole-mount preparation of the nasal mucosa for immunohistochemistry is a useful tool to analyze the morphology of olfactory receptor cells and axons.     

Dynamic changes in NADPH-diaphorase staining reflect activity of nitric oxide synthase: evidence for a dopaminergic regulation of striatal nitric oxide release

In fixed tissue, neuronal NADPH-diaphorase staining results from nitric oxide synthase (NOS) activity. Neuronal NOS only synthesizes nitric oxide once activated by the binding of Ca2+/calmodulin. We show here that neuronal NADPH-diaphorase staining is also dependent on Ca2+/calmodulin, implying that only activated NOS is detected. In addition, in bovine pulmonary endothelial cells, carbachol and bradykinin dramatically and rapidly increase the intensity of NADPH-diaphorase staining. Furthermore, administration of MK801, an NMDA antagonist, decreases neuronal NADPH-diaphorase staining. This suggests that the intensity of the NADPH-diaphorase staining is related to the level of enzyme activation at the moment of tissue fixation. The potential of exploiting this observation to detect cellular activation of NOS is illustrated by the observations that the intensity of NADPH-diaphorase staining in rat striatal neurones is decreased following systemic treatment with the D1-like dopamine receptor antagonist SCH23390, and increased by the D2-like antagonist eticlopride. These results therefore provide strong evidence that the NADPH-diaphorase reaction can be used to monitor NOS activity at a cellular level of resolution, and reveal a dopaminergic regulation of NOS activity in the striatum mediated by D1-like and D2-like dopamine receptors.     

DNA image cytometry on sections as compared with image cytometry on smears and flow cytometry in melanoma

The distribution and morphology of neurocalcin-immunopositive neurons have been studied in the rat accessory olfactory bulb. Different subsets of neurons displaying neurocalcin immunoreactivity were found in the glomerular layer, the external plexiform layer and the internal plexiform layer. The most abundant staining was detected in the glomerular layer where neurocalcin-immunoreactive periglomerular cells and external tufted cells were observed in the lateral glomeruli, whereas the central region of this layer was practically devoid of immunopositive neurons. In the external plexiform layer, medial tufted cells and Van Gehuchten cells displayed neurocalcin immunoreactivity. In the internal plexiform layer, interneurons classified as horizontal cells and vertical cells of Cajal were neurocalcin-immunoreactivity. In the internal plexiform layer, interneurons classified as horizontal cells and vertical cells of Cajal were neurocalcin-immunostained. The staining pattern for neurocalcin in the accessory olfactory bulb showed similarities with the immunostaining described in this brain region for another EF-hand calcium binding protein, calbindin D-28k. However, after double immunohistochemical labeling, colocalization of both proteins in the same neuron was not observed, reflecting a biochemical heterogeneity within morphologically homogeneous neuronal groups.     

The role of thrombocytes in allergic inflammation

Microencephalic rats were obtained through gestational (for the forebrain) or neonatal (for the cerebellum) administration of the DNA-alkylating agent methylazoxymethanol acetate (MAM), which selectively kills dividing cells during neurogenesis. In the microencephalic cerebellum the specific activity of calcium-dependent nitric oxide synthase (NOS) was decreased by 35-40% at 12, 28 and 70 days of age. Other neurochemical markers not related to granule cells (the neuronal population selectively compromised by neonatal MAM treatment), choline acetyltransferase (ChAT) and glutamate decarboxylase (GAD) were not decreased, but actually increased when determined as specific activity. In agreement with the decreased catalytic activity measured in the tube, the expression of neuronal NOS protein was attenuated as judged from immunohistochemistry and Western blotting. In the microencephalic forebrain, the specific calcium-dependent NOS activity measured in homogenates of the whole hemisphere was significantly increased as compared to normal animals. Accordingly, immunohistochemistry for neuronal NOS, as well as NADPH-diaphorase histochemistry revealed an apparent increase in the density of strongly reactive neurons in the underdeveloped cortex and striatum of microencephalic rats. The results reported here demonstrate that permanent alterations of neuronal NOS activity and expression occur when the development of the brain and its neuronal circuits are severely compromised. Furthermore, the permanent downregulation of neuronal NOS in the cerebellum of microencephalic rats may be exploited for the study of the role of NO in mechanisms of synaptic plasticity such as long term depression (LTD).     

An ethical responsibility for pain management

Recently, neuronal nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase has been elucidated to be the nitric oxide synthase (NOS) per se. In order to examine the existence and distribution of cerebrovascular nerve fibers containing these substances, NADPH-diaphorase histochemistry was applied to the cerebral blood vessels and the cranial ganglia known to innervate the cerebral vessels in the rat. Numerous nerve fibers with varicosities forming plexuses were observed in the circle of Willis and its branches. In addition, thick nerve bundles were seen to run along the wall of the internal ethmoidal artery. NADPH-diaphorase reaction was prominent in neurons of the sphenopalatine, otic and internal carotid ganglia. This study demonstrated, for the first time, the NADPH-diaphorase-containing nerve fibers in the cerebral vessels and ganglion cells in the parasympathetic and sensory ganglia known to innervate the cerebral vessels.     

Effects of some phenylethylamines in rhesus monkeys trained to discriminate (+)-amphetamine from saline

The distribution of intraepithelial nerve fibres and neuroendocrine cells within the surface and glandular epithelium of human nasal mucosa and larynx was examined using immunohistochemical techniques. Neuronal structures were immunostained for the general neuroendocrine marker protein gene-product (PGP) 9.5, and the two neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) using immunofluorescence and streptavidin-biotin-peroxidase complex (S-ABC) methods. Intraepithelial nerve fibres with free nerve endings contained PGP 9.5 and were found within the respiratory surface epithelium of the nasal mucosa and the squamous epithelium of the larynx. A subpopulation of these nerve fibres showed positive immunoreactivties with antibodies against SP and CGRP. Nerve fibres within the ductal epithelium of subepithelial excretory ducts passing the basal membrane and reaching the luminal part were detected. These nerve fibres showed CGRP-like immunoreactivity but not for SP. A dense network of nerve fibres within the squamous surface epithelium was detected in the subglottic and epiglottic region containing CGRP and SP in a small subpopulation of nerve fibres. Single intraepithelial taste buds in the epiglottic region and neuroendocrine cells within the subglottic epithelium expressed PGP 9.5.     

Characteristics of nitric oxide synthase type I of rat cerebellar astrocytes

We have previously reported that stimulation of astrocyte cultures by particular agonists and calcium ionophores induces cyclic GMP formation through activation of a constitutive nitric oxide synthase (NOS) and that astrocytes from cerebellum show the largest response. In the present work we have used rat cerebellar astrocyteenriched primary cultures to identify and characterise the isoform of NOS expressed in these cells. The specific NOS activity in astrocyte homogenates, determined by conversion of [3H]arginine to [3H]citrulline, was ten times lower than in homogenates from cerebellar granule neurons. Upon centrifugation at 100,000 g, the astroglial activity was recovered in the supernatant, whereas in neurons around 30% of the activity remained particulate. The cytosolic NOS activities of both astrocytes and granule neurons displayed the same Km for L-arginine, dependency of calcium, and sensitivity to NOS inhibitors. Expression of NOS-I in astrocyte cytosolic fractions was revealed by Western blot with a specific polyclonal antiserum against recombinant NOS-I. Double immunofluorescence labelling using anti-glial fibrillary acidic protein (GFAP) and anti-NOS-I antibodies revealed that a minor population of the GFAP-positive cells, usually in clusters, presented a strong NOS-I immunostaining that was predominantly located around the nuclei and had a granular appearance, indicating association with the endoplasmic reticulum-Golgi system. Astrocytes of stellate morphology also showed immunoreactivity in the processes. Similar staining was observed with the avidin-biotin-peroxidase complex using different anti-NOS-I antisera. With this method the majority of cells showed a weak NOS-I immunoreactivity around the nuclei and cytosol. A similar pattern was observed with the NADPH-diaphorase reaction. These results demonstrate that the NOS-I expressed in astrocytes presents the same biochemical characteristics as the predominant neuronal isoform but may differ in intracellular location.     

Organization of inhibition in the rat olfactory bulb external plexiform layer

1. Intracellular recordings were made from the output neurons (mitral and tufted cells) of the rat olfactory bulb during electrical orthodromic stimulation of the olfactory nerve layer (ONL) and antidromic stimulation of the lateral olfactory tract and posterior piriform cortex (pPC) to test for physiological differences among the neuron types. Many of these neurons were identified by intracellular injections of biocytin, and others were identified by their pattern of antidromic activation. 2. Both marked and unmarked mitral cells showed large inhibitory postsynaptic potentials (IPSPs) in response to antidromic stimulation of the pPC, whereas tufted cells exhibited small IPSPs in response to pPC stimulation. Tufted cells, however, showed large IPSPs in response to ONL stimulation. In many cases, these tufted cell responses to ONL stimulation were larger than the mitral cell responses. The marked superficial tufted cells, those with basal dendrites in the superficial sublayer of the external plexiform layer (EPL), had the smallest IPSPs in response to pPC stimulation. These data support anatomic observations suggesting that the granule cell populations responsible for the IPSPs may be different for mitral and for superficial tufted cells. 3. The different types of output cells also showed differences in their responses to orthodromic stimulation. Type I mitral cells, which have basal dendrites confined to the deep sublayer of the EPL, were significantly less excitable by ONL stimulation than were the type II mitral cells, which have basal dendrites distributed within the intermediate sublayer of the EPL. Half of the type I mitral cells could not be excited at all by ONL stimulation. Superficial tufted cells showed even greater orthodromic excitability than type II mitral cells, usually responding to ONL stimulation with two or more spikes. 4. The ionic basis of the IPSPs in the superficial tufted cells appeared similar to those described for mitral cells. These IPSPs could be reversed by chloride injection and were associated with increased membrane conductance. 5. For both mitral and tufted cells, the number of ONL electrodes evoking IPSPs was greater than the number evoking spikes. These data suggest a kind of center-surround organization of inputs to these cells from the ONL, although this does not yet imply that the sensory receptive field of these output cells has a center-surround organization. 6. In conclusion, the properties of rat olfactory bulb output cells correlate with the sublayers of the EPL in which their basal dendrites lie.(ABSTRACT TRUNCATED AT 400 WORDS)     

MK-801 and male odours induce c-fos expression in the AOB of juvenile female mice

The odours of adult males, which accelerate the timing of puberty of female mice, activate c-fos in the accessory olfactory bulb (AOB). To test the hypothesis that NMDA receptors are involved in the male odour-induced increase in c-fos expression, we studied the effects of the non-competitive NMDA receptor agonist MK-801 on male odour-induced c-fos expression in the AOB of juvenile female mice. Surprisingly, MK-801 increased FOS-like immunoreactivity (FLI) within the AOB in the absence of male odour and had no effect on male odour-induced c-fos expression. We suggest that MK-801 increases AOB mitral cell activity by disinhibiting GABAergic granule cells, resulting in increased c-fos expression throughout the AOB.     

Neuroendocrine differentiation and nerves in human adrenal cortex and cortical lesions

Neuroendocrine differentiation and nerve distribution were studied in sections from human cortex (n=11) and cortical lesions (hyperplasias, n=9; adenomas, n=13; carcinomas, n=14) with four markers, namely chromogranin A(CgA), synaptophysin (SYN), neuron-specific enolase (NSE), protein gene product (PGP) 9.5 and small synaptic vesicle protein (SV)2. All but two cases expressed neuroendocrine differentiation. NSE was the most commonly occurring marker and the NSE immunoreactive cells were detected in normal cortex, mainly in zona glomerulosa, as well as in adenomas and carcinomas. SYN and PGP 9.5 immunoreactive cells were especially prominent in the carcinomas, while SV2 immunoreactive cells were seen mainly in normal cortex. The difference in distribution pattern of the neuroendocrine markers between adenomas and carcinomas was not so distinct that it can be used for histopathological diagnosis. The significance of neuroendocrine differentiation in cortex and cortical lesions is uncertain, but may reflect an involvement in special hormonal functions. No obvious relationship was found between the clinical syndromes and the degree of neuroendocrine differentiation. Three of the neuroendocrine markers also visualized nerve structures. PGP 9.5, which is regarded as the most 'general' nerve marker, visualized more nerve structures than did the other markers. Normal cortex contained most immunoreactive nerves, whereas they were less numerous in hyperplasias and sparse or even absent in the neoplasms. The nerves appeared among the parenchymal cells but were particularly prominent around vessels. The results suggest that the cortical nerves influence not only the regulation of the blood supply but also the hormonal regulation at the cellular level.