Glucose transporter plasticity during memory processing

Various types of learning, including operant conditioning, induce an increase in cellular activation concomitant with an increase in local cerebral glucose utilization (LCGU). This increase is mediated by increased cerebral blood flow or changes in brain capillary density and diameter. Because glucose transporters are ultimately responsible for glucose uptake, we examined their plastic expression in response to cellular activation. In vitro and in vivo studies have demonstrated that cerebral glucose transporter 1 (GLUT1) expression consistently parallels changes in LCGU. The present study is the first to investigate the effect of memory processing on glucose transporters expression. Changes in GLUT expression produced by training in an operant conditioning task were measured in the brain of CD1 mice. Using semi-quantitative immunohistochemistry, Western blot and real time RT-PCR the cerebral GLUT1 and GLUT3 expression was quantified immediately, 220 min and 24 h following training. Relative to sham-trained and naive controls, operant conditioning training induced an immediate increase in GLUT1 immunoreactivity level in the hippocampus CA1 pyramidal cells as well as in the sensorimotor cortex. At longer post-learning delays, GLUT1 immunoreactivity decreased in the sensorimotor cortex and putamen. Parallel to the changes in protein levels, hippocampus GLUT1 mRNA level also increased immediately following learning. No effect of learning was found on hippocampal GLUT3 protein or mRNA expression. Measures of changes in glucose transporters expression present a link between cellular activation and glucose metabolism. The learning-induced localized increases in GLUT1 protein as well as mRNA levels observed in the present study confirm the previous findings that GLUT1 expression is plastic and respond to changes in cellular metabolic demands.

Trigeminal uptake and clearance of inhaled manganese chloride in rats and mice

Inhaled manganese (Mn) can enter the olfactory bulbs via the olfactory epithelium, and can then be further transported trans-synaptically to deeper brain structures. In addition to olfactory neurons, the nasal cavity is innervated by the maxillary division of the trigeminal nerve that projects to the spinal trigeminal nucleus. Direct uptake and transport of inhaled metal particles in the trigeminal system has not been investigated previously. We studied the uptake, deposition, and clearance of soluble Mn in the trigeminal system following nose-only inhalation of environmentally relevant concentrations. Rats and mice were exposed for 10-days (6 h/day, 5 days/week) to air or MnCl2 aerosols containing 2.3 +/- 1.3 mg/m3 Mn with mass median aerodynamic diameter (MMAD) of 3.1 +/- 1.4 microm for rats and 2.0 +/- 0.09 mg/m3 Mn MnCl2 with MMAD of 1.98 +/- 0.12 microm for mice. Mn concentrations in the trigeminal ganglia and spinal trigeminal nucleus were measured 2 h (0-day), 7-, 14-, or 30-days post-exposure using proton induced X-ray emission (PIXE). Manganese-exposed rats and mice showed statistically elevated levels of Mn in trigeminal ganglia 0-, 7- and 14-days after the 10-days exposure period when compared to control animals. The Mn concentration gradually decreased over time with a clearance rate (t1/2) of 7-8-days. Rats and mice were similar in both average accumulated Mn levels in trigeminal ganglia and in rates of clearance. We also found a small but significant elevation of Mn in the spinal trigeminal nucleus of mice 7-days post-exposure and in rats 0- and 7-days post-exposure. Our data demonstrate that the trigeminal nerve can serve as a pathway for entry of inhaled Mn to the brain in rodents following nose-only exposure and raise the question of whether entry of toxicants via this pathway may contribute to development of neurodegenerative diseases.

Dynamics of volume transmission in the brain. Focus on catecholamine and opioid peptide communication and the role of uncoupling protein 2

This review focuses on transmitter-receptor mismatches in the brain, which is one of the hallmarks of the Volume Transmission (VT) concept, and how this phenomenon may be related to local temperature gradients created by brain uncoupling protein 2 (UCP2), which uncouples oxidative phosphorylation from ATP synthesis, hereby generating heat. Recent studies on transmitter-receptor mismatches have revealed dopamine and opioid peptide receptor mismatches in the intercalated islands of the amygdala, which are GABAergic cell clusters regulating amygdaloid output. Such mismatches have also been found in regions belonging to the extended amygdala and the nucleus accumbens shell. Now substantial UCP2 immunoreactivity has been found within the above transmitter-receptor mismatch regions, suggesting that UCP2 may enhance diffusion and convection of DA and opioid peptides in such regions by generation of local temperature gradients, thereby contributing to a dynamic regulation of VT.

Receptor heteromerization in adenosine A2A receptor signaling: relevance for striatal function and Parkinson's disease

Recently evidence has been presented that adenosine A2A and dopamine D2 receptors form functional heteromeric receptor complexes as demonstrated in human neuroblastoma cells and mouse fibroblast Ltk- cells. These A2A/D2 heteromeric receptor complexes undergo coaggregation, cointernalization, and codesensitization on D2 or A2A receptor agonist treatments and especially after combined agonist treatment. It is hypothesized that the A2A/D2 receptor heteromer represents the molecular basis for the antagonistic A2A/D2 receptor interactions demonstrated at the biochemical and behavioral levels. Functional heteromeric complexes between A2A and metabotropic glutamate 5 receptors (mGluR5) have also recently been demonstrated in HEK-293 cells and rat striatal membrane preparations. The A2A/mGluR5 receptor heteromer may account for the synergism found after combined agonist treatments demonstrated in different in vitro and in vivo models. D2, A2A, and mGluR5 receptors are found together in the dendritic spines of the striatopallidal GABA neurons. Therefore, possible D2/A2A/mGluR5 multimeric receptor complexes and the receptor interactions within them may have a major role in controlling the dorsal and ventral striatopallidal GABA neurons involved in Parkinson's disease and in schizophrenia and drug addiction, respectively.

Interactions among adenosine deaminase, adenosine A(1) receptors and dopamine D(1) receptors in stably cotransfected fibroblast cells and neurons

The role of adenosine deaminase in the interactions between adenosine A(1) and dopamine D(1) receptors was studied in a mouse fibroblast cell line stably cotransfected with human D(1) receptor and A(1) receptor cDNAs (A(1)D(1) cells). Confocal laser microscopy analysis showed a high degree of adenosine deaminase immunoreactivity on the membrane of the A(1)D(1) cells but not of the D(1) cells (only cotransfected with human D(1) receptor cDNAs). In double immunolabelling experiments in A(1)D(1) cells and cortical neurons a marked overlap in the distribution of the A(1) receptor and adenosine deaminase immunoreactivities and of the D(1) receptor and adenosine deaminase immunoreactivities was found. Quantitative analysis of A(1)D(1) cells showed that adenosine deaminase immunoreactivity to a large extent colocalizes with A(1) and D(1) receptor immunoreactivity, respectively. The A(1) receptor agonist caused in A(1)D(1) cells and in cortical neurons coaggregation of A(1) receptors and adenosine deaminase, and of D(1) receptors and adenosine deaminase. The A(1) receptor agonist-induced aggregation was blocked by R-deoxycoformycin, an irreversible adenosine deaminase inhibitor. The competitive binding experiments with the D(1) receptor antagonist [(3)H]SCH-23390 showed that the D(1) receptors had a better fit for two binding sites for dopamine, and treatment with the A(1) receptor agonist produced a disappearance of the high-affinity site for dopamine at the D(1) receptor. R-Deoxycoformycin treatment, which has previously been shown to block the interaction between adenosine deaminase and A(1) receptors, and which is crucial for the high-affinity state of the A(1) receptor, also blocked the A(1) receptor agonist-induced loss of high-affinity D(1) receptor binding. The conclusion of the present studies is that the high-affinity state of the A(1) receptor is essential for the A(1) receptor-mediated antagonistic modulation of D(1) receptors and for the A(1) receptor-induced coaggregates of A(1) and adenosine deaminase, and of D(1) and adenosine deaminase. Thus, the confocal experiments indicate that both A(1) and D(1) receptors form agonist-regulated clusters with adenosine deaminase, where the presence of a structurally intact adenosine deaminase bound to A(1) receptors is important for the A(1)-D(1) receptor-receptor interaction at the level of the D(1) receptor recognition.

Immunohistochemical localization and quantification of glucose transporters in the mouse brain

A family of seven facilitative glucose transporters (Glut1-5, 7 and 8) mediates the cellular uptake of glucose. In the brain, Glut2, Glut5 and Glut8 are found at relatively low levels whereas Glut1, Glut3 and Glut4 were reported in abundance in several brain regions. Using immunofluorescence, this study investigated, compared and quantified the localization of the brain major glucose transporters, Glut1, Glut3 and Glut4, in the different cerebral areas of CD1 mice. Most of the staining of Glut1, Glut3 and Glut4 in the mouse brain coincides with observations made in rats. The results confirm the cortical neuropil distribution of Glut3, the prominence of this transporter in the mossy fiber field of the hippocampus and the Glut3 and Glut4 immunostaining of the hippocampal pyramidal cell layer. The present study also reports novel localizations of the transporters such as the presence of Glut3 in neuronal perikarya, Glut4-labeled neurons in the CA3 of the hippocampus and the subiculum. In the cerebellum, Glut3 shows subcellular localization to the base of the Purkinje cell bodies near the axon hillock. Furthermore, an important population of Golgi cells was found to be strongly immunostained for Glut4 in the granular cell layer of the cerebellum. The quantification results suggest that the relative abundance of Glut1 in the frontal and motor cortices coincides well with the high-energy demands of these brain regions. However, the Glut4-selective abundance in cerebral motor areas supports its suggested role in providing the energy needed for the control of the motor activity. The reported neuropil distribution of Glut3 seems to uphold its suggested role in synaptic energy provision and neurotransmitter synthesis. We conclude that the cellular and regional distributions of the glucose transporters in the rodent brain seem to be relevant to their corresponding functions.

Time-dependent sensitization of corticotropin-releasing hormone, arginine vasopressin and c-fos immunoreactivity within the mouse brain in response to tumor necrosis factor-alpha

Stressor or cytokine treatments, such as interleukin-1beta, promote time-dependent alterations of hypothalamic-pituitary-adrenal functioning, including increased arginine vasopressin stores within corticotropin-releasing hormone (CRH) terminals in the external zone of the median eminence. Likewise, we have previously shown that the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), provoked a time-dependent sensitization of neuroendocrine and brain monoamine activity. To further explore the protracted consequences of TNF-alpha, the present investigation determined whether the cytokine sensitized activity of neuroendocrine regulatory brain regions, as assessed by c-fos expression, and had protracted consequences on amygdaloid CRH, as well as hypothalamic corticotropin secretagogues. Indeed, immunoreactivity for arginine vasopressin and corticotropin-releasing hormone, and their colocalization within cell terminals of the median eminence, varied over time following an initial 4.0-microg tumor necrosis factor-alpha treatment, peaking after 7 days and normalizing within 28 days. Within the central amygdala, a sensitization effect was evident as reflected by increased CRH immunoreactivity, but this effect required re-exposure to the cytokine, unlike the median eminence changes that simply evolved with the passage of time. As well, tumor necrosis factor-alpha provoked a marked sensitization of c-fos staining within the paraventricular nucleus of the hypothalamus, supraoptic nucleus and the central amygdala. From these data we suggest that tumor necrosis factor-alpha influences responsivity of stressor-reactive brain regions and has protracted effects on central neuropeptide expression within the hypothalamus and central amygdala, although the time course for the effects vary across brain regions. Evidently, exposure to tumor necrosis factor-alpha may promote neuroplasticity of brain circuits involved in mediating neuroendocrine, sickness or inflammatory responses. It is suggested that such a sensitization may influence the response to immunological and traumatic insults and may thus be relevant to behavioral pathology.

Neurochemical characterization and distribution of enteric GABAergic neurons and nerve fibres in the human colon

GABA, somatostatin and enkephalin are neurotransmitters of enteric interneurons and comprise part of the intrinsic neural circuits regulating peristalsis. Within the relaxation phase of reflex peristalsis, nitric oxide (NO) is released by inhibitory motor neurons and perhaps enteric interneurons as well. Previously, we identified by GABA transaminase (GABA-T) immunohistochemistry, a subpopulation of GABAergic interneurons in the human colon which also contain NO synthase activity and hence produce NO. In this study, we have examined further the capacity for cotransmission within the GABAergic innervation in human colon. The expression of two important neuropeptides within GABAergic neurons was determined by combined double-labelled immunocytochemistry using antibodies for GABA-T, enkephalin and somatostatin, together with the demonstration of NO synthase-related NADPH diaphorase staining in cryosectioned colon. Both neuropeptides were found in GABAergic neurons of the colon. The evidence presented herein confirms the colocalization of NO synthase activity and GABA-T immunoreactivity in subpopulations of enteric neurons and further allows the neurochemical classification of GABAergic neurons of the human colon into three subsets: (i) neurons colocalizing somatostatin-like immunoreactivity representing about 40% of the GABAergic neurons, (ii) neurons colocalizing enkephalin-like immunoreactivity, about 9% of the GABAergic neurons and (iii) neurons colocalizing NO synthase activity, about 23% of the GABAergic neurons. This division of GABAergic interneurons into distinct subpopulations of neuropeptide or NO synthase containing cells is consistent with and provides an anatomical correlate for the pharmacology of these transmitters and the pattern of transmitter release during reflex peristalsis.

Regional distribution of neural cell adhesion molecule immunoreactivity in the adult rat telencephalon and diencephalon. Partial colocalization with heparan sulfate proteoglycan immunoreactivity

In the present paper immunocytochemical analysis at the fluorescence microscopical level has been performed of neural cell adhesion. molecule (NCAM) immunoreactivity in the adult rat tel- and diencephalon in order to further substantiate the highly selective neuronal localization of NCAM immunoreactivity, using an affinity purified rabbit antiserum recognizing homologous NCAM proteins from rat brain. Also, double immunolabelling experiments were performed with monoclonal antibodies specific for heparan sulfate related epitopes or gamma-aminobutyric acid (GABA) to establish in which cell populations a colocalization existed with immunoreactive heparan sulfate proteoglycans of GABA. Within the neocortex NCAM immunoreactivity was exclusively localized to the area of the cell membrane of soma and proximal dendrites of subsets of large pyramidal nerve cells of the layer 5 of the frontoparietal cortex. Within the dorsal hippocampus, the NCAM immunoreactivity was exclusively located to the cell surface area of the pyramidal cell bodies of area CA2. Two colour immunofluorescence procedures demonstrated a colocalization of NCAM and 3G10 but not 10E4 immunoreactivities in the cell surface area of many of the NCAM-positive nerve cell bodies of these two regions. Within the thalamus, strong NCAM immunoreactivity was exclusively demonstrated at all rostrocaudal levels of the reticular thalamic nucleus. The horizontal band of NCAM immunoreactivity was not continuous, but split up into patches of NCAM immunoreactivity within groups of nerve cell bodies. When analysing the number of cells per unitary square in the rostrocaudal direction, a significant increase of positive cells was found in the rostral and middle thirds versus the caudal third of the reticular thalamic nucleus. Many of the cell bodies with NCAM immunoreactivity in their cell surface are showed cytoplasmic GABA immunoreactivity. In the three regions shown to contain NCAM immunoreactivity, proteins of the NCAM type may play a special role for the maintenance of the synaptic structure. The findings also suggest that the sulfated proteoglycans and NCAM can interact in the regulation of cell-cell interaction via adhesion. In the reticular thalamic nucleus NCAM molecules may be part of a set of cell-adhesion molecules involved in a structural organization of the nucleus, which allows it to play a key role in relating cortical maps to thalamic maps.

Differentiating neuroblastoma of pituitary gland: neuroblastic transformation of epithelial adenoma cells. Case report

The authors report the case of a 40-year-old woman with a 12-year history of irregular menses, amenorrhea, infertility, galactorrhea, a slightly elevated prolactin level, and a slowly growing pituitary adenoma. She developed recent onset of visual symptoms, prompting craniotomy for removal of an intrasellar tumor. Following surgery, her vision and prolactin levels returned to normal. Light microscopic and immunohistochemical examination of the tumor revealed it to be a neuroblastoma, which was immunohistochemically positive for synaptophysin, S-100 protein, and oxytocin. The neoplasm contained prolactin-positive neuroblastic and pituitary epithelial cells. No other pituitary hormones were found. Electron microscopy demonstrated two cell types: one with frequent neuritic processes containing neurosecretory granules and showing synaptic specialization, and another one compatible with epithelial adenohypophyseal cells. A few cells had ultrastructural features that were transitional between neuronal cells and granulated epithelial cells. Agranular folliculostellate cells were also identified. Immunoelectron microscopy demonstrated prolactin granules in the cytoplasm of the epithelial cells, in a few transitional cells, and in scattered neuritic processes. Ultrastructural and immunohistochemical features of the tumor suggested a transformation of pituitary epithelium to neuroblastic cells. Hyperprolactinemia and associated clinical symptoms may in part be attributed to selective prolactin secretion by neoplastic cells that were differentiating into adenomatous pituitary cells and, to a lesser extent, to cells differentiating into a neuroblastic line. Compression of pituitary stalk might also have been a contributory factor to the increased prolactin levels. Moreover, the oxytocin produced by the neuroblastic cells was considered an additional stimulus for prolactin secretion by neoplastic cells or by the normal pituitary.

Localization of GABAA receptor immunoreactivity in NO synthase positive myenteric neurones

GABAA receptors were localized within laminar preparations of the rat distal colon myenteric plexus using a monoclonal antibody (mAb 62-3G1) to the affinity purified GABAA receptor/benzodiazepine receptor/Cl- channel complex. The immunofluorescence procedure showed that approximately half of the myenteric ganglion cells displayed extensive GABAA receptor labelling of their soma. This population was further characterised by treating some GABAA-receptor-labelled laminar preparations for the histochemical demonstration of nitric oxide (NO) synthase-related NADPH-dependent diaphorase activity. A subpopulation of the GABAA-receptor-immunoreactive cells (35%) were also found to display intense NO-synthase-related activity. These findings extend our understanding of the GABAA-receptor-related innervation of the rat gut wall herein referred to as 'A-GABAergic' and provides an anatomical basis for the pharmacologically-identified GABA-nitrergic pathway in the mammalian gut.

Immunopositive GABAergic neural sites display nitric oxide synthase-related NADPH diaphorase activity in the human colon

In the enteric nervous system, gamma-aminobutyric acid (GABA) is a transmitter of interneurons which are proposed to innervate excitatory and inhibitory motor neurons. Nitric oxide (NO) is a putative transmitter of enteric inhibitory motor nerves targeted by GABA. In addition, NO is synthesized by a variety of enteric nerves throughout the gut wall indicative of its potential to be a transmitter of other nerve types, including interneurons. We sought to determine if some populations of nitrergic neurons are interneurons in human infant colon. As enteric neural GABA is exclusive to interneurons, colocalization with NO synthase-related NADPH diaphorase was examined. GABA-transaminase (GABA-T) immunohistochemistry was used to identify GABAergic neurons and a histochemical protocol was used as a marker of neuronal NO synthase-related NADPH diaphorase activity in enteric layers. GABA-T immunoreactive neurons were seen in the ganglionated nerve networks of the myenteric and submucosal layers. GABA-T immunoreactive fibres were also present in the longitudinal and circular muscle layers. A subpopulation of GABA-T immunoreactive neurons within both the myenteric and submucosal ganglia express NO synthase-related activity. This colocalization extends further to a subpopulation of fibers within the muscle layers. These findings strongly suggest that in addition to its role in inhibitory motor neurons, NO may also be a transmitter of enteric interneurons.

Neural sites of the human colon colocalize nitric oxide synthase-related NADPH diaphorase activity and neuropeptide Y

BACKGROUND/AIMS

Nitric oxide and neuropeptide Y (NPY) exert similar biological actions in the mammalian intestine including modulation of food intake, blood flow, motility, and secretion. In addition, these substances coexist in submucosal secretomotor neurons of the rodent intestine. The aim of this study was to determine the relative disposition of elements displaying NPY immunoreactivity and NO synthase-related nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity in the nerve networks of the human infant colon.

METHODS

Transverse and longitudinal sections, treated for immunohistofluorescent detection of NPY and then processed for NO synthase-related NADPH diaphorase histochemistry, were examined.

RESULTS

Neural elements containing NPY immunoreactivity and NO synthase-related activity were identified in the external muscle layers, myenteric plexus, and all nerve layers of the submucosa, including Henle's plexus, the intermediate nerve layer, and Meissner's plexus. Perivascular NPY-immunoreactive nerve fibers did not contain NO synthase activity. There were no nitrergic perivascular nerve fibers. NPY-immunoreactive endocrine cells in the mucosa did not display NO synthase-related activity.

CONCLUSIONS

These findings provide anatomical data indicating that NPY immunoreactivity and NO synthase-related activity are extensively colocalized in all layers of the human infant gut wall.

Generalized presence of a PEC-60-like peptide in catecholamine neurones

PEC-60, a 60-residue intestinal peptide structurally related to the pancreatic secretory type of trypsin inhibitor, has been isolated, characterized and molecularly cloned. It shows biological activity as a hormone in both the gastrointestinal tract and in the immune system. We now report immunohistochemical evidence suggesting its neural localization exclusively within central and peripheral catecholamine (CA) neurones. PEC-60-like immunoreactivity was present in cell bodies, dendrites and nerve terminals of virtually all catecholamine neurones examined and including the noradrenergic gland cells of the adrenal medulla. PEC-60-like immunoreactivity was not seen, however, within the tyrosine hydroxylase-positive but CA-negative arcuate neurones producing growth hormone releasing hormone. The findings open up the possibility that a PEC-60-like peptide may represent a generalized co-transmitter in the peripheral and central CA neurones.

Distribution of nitric oxide synthase activity in arterioles and venules of rat and human intestine

NO is produced within peripheral blood vessels through the action of the differentially distributed constitutive and inducible NO synthase isoforms in the vessel wall. As in other sites in the periphery, NO exerts local vasodilatory actions in the gastrointestinal microvasculature and is proposed to play a role in enteric vasomotor regulation. Using NO synthase histochemistry and endothelial cell immunohistochemistry, we provide the first anatomic evidence of NO synthesis in both endothelial and smooth muscle cells of submucosal blood vessels in the rat and human intestine. The findings of this study indicate that 1) as in the periphery, both the endothelial and vascular smooth muscle cells of the microvessels irrigating the rat and human intestinal wall possess NO synthesis potential, 2) NO synthase activity is predominantly localized to discrete subcellular patches, and 3) the source of NO within the vascular wall, either intimal or medial, should be a consideration in future studies in terms of the relative contribution of these sources of vasomotor tone in the rat and human gut wall.

Demonstration of benzodiazepine receptors in submucosal neurons of the gastrointestinal tract

Benzodiazepine (BZ) receptors were visualized in laminar preparations of the rat colon submucosa, using a fluorescent derivative of the benzodiazepine receptor ligand desdiethyl fluorazepam, Bodipy RO-1986 (50 nM). Collateral confirmation of the results obtained were sought through immunohistochemistry, using a monoclonal antibody (62-3GI) for benzodiazepine cell receptors. Both procedures showed that a large proportion of ganglia in the colon submucosa displayed cells with extensive labelling of their soma. Nerve fibres and processes, blood vessels and vascular nerve bundles were not labelled. Fluorescent ligand-labelling could be reduced, using the BZ receptor ligand diazepam (5 microM). These findings provide an anatomical basis for the previously described neuropharmacology of BZ in the gut.

Nitric oxide synthase distribution in the rat intestine: a histochemical analysis

BACKGROUND

Nitric oxide is an inhibitory transmitter of nonadrenergic, noncholinergic neurons and is purported to be an endothelium-derived relaxant-type factor in the mammalian gut. This study aimed to provide a complete report on the distribution of NO synthase in the rat small and large intestine.

METHODS

NO synthase was visualized histochemically through this enzyme's reduced nicotinamide adenine dinucleotide phosphate diaphorase activity and the distribution of staining within the gut wall.

RESULTS

The presence of NO synthase activity in myenteric neurons and their efferents to the circular muscle was confirmed. The largest proportion of stained cells per ganglion was found in the ileum, and the smallest proportion was in the colon. Stained neural elements were also found within the submucosa throughout the intestine. Stained cells within the myenteric and submucous nerve plexi displayed both type I and type II morphologies, with the latter being more numerous. In addition to neural staining, submucosal arterioles showed a regular pattern of small patches of staining unrelated to any perivascular innervation.

CONCLUSIONS

These findings indicate an extensive neural and vascular localization of NO generation potential throughout the wall of the rat intestine, thus providing a structural basis for the functional diversity of NO.

Histochemical localization of nitric oxide-synthesizing neurons and vascular sites in the guinea-pig intestine

Laminar preparations of fixed segments of the guinea-pig intestine were examined for nitric oxide synthase activity using reduced nicotinamide adenine dinucleotide phosphate and nitroblue tetrazolium salt as substrates. Under conditions specific for detecting nitric oxide synthase-related diaphorase activity, a subpopulation of neural elements in the myenteric plexus, deep muscular plexus and submucosa were intensely stained. Intensely stained nerve fibres were distributed throughout the meshworks of the myenteric plexus and its innervation of the circular muscle, and in the submucosa within Henle's plexus. Intensely stained nerve cells and their processes were evident in most myenteric ganglia but were rare in ganglia of Henle's plexus. Stained ganglion cells comprised types I, II and VI of the morphologically defined enteric nerve cells. Stained neural elements were increasingly prevalent within successively more caudal segments of the intestine. In addition to neuronal staining, arterioles of the submucosal vascular network displayed distinct, punctate patches of staining distributed over their surface. Perivascular nerve fibre staining was absent. These results show nitric oxide synthase activity to be present within neurons and fibres of the major enteric nerve layers and within submucosal blood vessels throughout the guinea-pig small and large intestine.

Immunoelectron microscopy of Rosenthal fibers

Seventeen intracerebral gliomas containing Rosenthal fibers (RF) were studied by an immunoperoxidase method for localization of ubiquitin (UB), glial fibrillary acidic protein (GFAP), desmin and vimentin (VIM). The majority of RF showed an immunohistochemically negative core surrounded by a ring of overlapping reactions for UB, GFAP and VIM. Many RF were entirely negative for UB and intermediate filaments (IF). Immunoelectron microscopic localization of UB and GFAP was performed on seven selected tumors. UB was found in all RF and on IF in the proximity of RF. GFAP reaction was localized on astrocytic IF, including those trapped within RF, and within the granular component of some RF. In contrast to the light microscopic studies, neither GFAP- nor UB-negative RF were found on immunoelectron microscopy. VIM reaction on IF and a few RF was demonstrated in one tumor processed at low temperature into Lowicryl; it was much weaker than that for GFAP. Many cells with RF contained lysosome-like inclusions with material displaying electron density similar to adjacent RF; few of these inclusions were reactive for UB. It is concluded that RF formation is associated with ubiquitination of astrocytic IF. GFAP- and VIM-immunoreactive IF and products of their disintegration contribute to RF material. It is also suggested that the lysosomal system of astrocytes partially degrades RF.

Demonstration and nature of endothelin-3-like immunoreactivity in somatostatin and choline acetyltransferase-immunoreactive nerve cells of the neostriatum of the rat

Using a rabbit endothelin-1 (ET-1) antiserum together with a goat-anticholineacetylase antiserum or a mouse anti-somatostatin antiserum it was possible by means of double immunolabelling procedures to demonstrate ET-like immunoreactivity in striatal nerve cell bodies of the rat, which were shown to contain either cholineacetylase or somatostatin immunoreactivity. Absorption studies with ET-3, ET-1 or big ET-1 indicated that the ET-like immunoreactivity was ET-3 like. In agreement the radioimmunoassay showed that ET-3-like immunoreactivity was present in higher concentrations than ET-1-like immunoreactivity in the neostriatum and other brain areas. Characterization by reversed phase HPLC revealed, however, that a major portion of the neostriatal ET-3-like immunoreactivity was not identical to ET-3. The nature of neuronal ET in the rat may thus be more complicated than hitherto assumed.

Central peptidergic neurons as targets for glucocorticoid action. Evidence for the presence of glucocorticoid receptor immunoreactivity in various types of classes of peptidergic neurons

By means of double immunolabeling procedures it has been possible to demonstrate glucocorticoid receptor (GR) immunoreactivity (IR) in large numbers of various peptidergic neurons of the brain including neurons containing gastrointestinal peptides, opioid peptides, and peptides with a hypothalamic hormone function. For each peptide system, however, marked heterogeneities exist among brain regions. Thus, in the neocortex and the hippocampal formation most of the brain peptide neurons lack GR IR, while the same types of peptide neurons in the arcuate and paraventricular nucleus [e.g. neuropeptide Y (NPY), somatostatin (SRIF) and the cholecystokinin (CCK) neurons] possess strong GR IR. Furthermore, in the arcuate, parvocellular part of the paraventricular nuclei and the central amygdaloid nucleus practically all the peptidergic neurons are strongly GR IR, while in the lateral hypothalamus, mainly the neurotensin (NT) and galanin (GAL) IR neurons are GR IR. These marked differences among areas probably reflect functional differences dependent upon their participation in stress regulated circuits. All the paraventricular NT, corticotropin-releasing factor (CRF), growth hormone-releasing factor (GRF), thyrotropin-releasing hormone (TRH) and SRIF IR neurons appear to contain GR IR, while the luteinizing hormone-releasing hormone (LHRH) IR neurons lack GR IR, underlying the importance of glucocorticoids (GC) in controlling endocrine function. Finally, the GC may influence pain and mood control mainly via effects on enkephalin (ENK) neurons especially in the basal ganglia (mood) and on all beta-endorphin (beta-END) neurons of the arcuate nucleus, while most of the dynorphin neurons are not directly controlled by GC.

Substance P and calcitonin gene-related peptide: immunohistochemical localisation and microvascular effects in rabbit skeletal muscle

1. The distribution and microvascular effects of substance P (SP) and calcitonin gene-related peptide (CGRP) were studied in the rabbit tenuissimus muscle using immunohistochemistry and intravital microscopy. 2. Individual fibers within nerve bundles and along blood vessels in the muscle were found to be immunoreactive (IR) for both SP and CGRP, thus showing an apparently complete coexistence for these peptides. In dorsal root ganglia most SP-positive cells were also CGRP-IR, but the latter cells were somewhat more numerous than SP-IR cells. 3. When applied topically to the muscle, both SP and CGRP increased blood flow in a dose-dependent manner, but CGRP was more potent and caused responses of longer duration. Both SP and CGRP dilated transverse arterioles, but they had little or no effect on the smaller terminal arterioles. This resulted in a redistribution of blood flow to the connective tissue adjacent to the muscle. 4. SP, but not CGRP, elicited vigorous vasomotion in larger arterioles and caused the formation of aggregates of platelets and leukocytes in the venules. Neither flow increase, nor vasomotion or aggregate formation were influenced by pretreatment of the animals with mepyramine, cimetidine or indomethacin. Capsaicin (1 microM) had a powerful effect on transverse arterioles resembling that of both SP and CGRP. 5. It is concluded that some of the vascular effects hitherto ascribed to SP on the basis of nerve stimulation and application of capsaicin might, at least in part, be due to release of CGRP.

Striato-nigral dynorphin and substance P pathways in the rat. I. Biochemical and immunohistochemical studies

The effect of striatal ibotenic acid lesions on dynorphin-, substance P- and enkephalin-like immunoreactivities in the substantia nigra has been studied with immunohistochemistry as well as biochemistry. A comparison was made with the effects produced by intranigral ibotenic acid lesion and by 6-hydroxy-dopamine injection into the medial forebrain bundle. In addition, the effect of the striatal lesions on nigral glutamic acid decarboxylase (GAD)-positive structures was analysed with immunohistochemistry. The effect of the lesions was analysed functionally in the Ungerstedt rotational model, in order to obtain a preliminary evaluation of the extent of the lesions. The striatal lesions produced a parallel depletion of dynorphin and substance P levels in the substantia nigra, pars reticulata, ipsilateral to the treated side, which was dependent upon the extent and location of the lesion. Ibotenic acid lesions into the tail and the corpus of the striatum produced stronger nigral-peptide depletion than lesions in the head and the corpus of the striatum. Comparison of placement of lesions and localization of depleted area in the substantia nigra revealed a topographical relationship. Furthermore, the nigral depletion patterns of dynorphin and substance P were similar. The immunohistochemical analysis revealed that also GAD-positive fibers in the pars reticulata to a large extent disappeared after striatal lesions, in parallel to the dynorphin- and substance P-positive fibers. However, the depletion was less pronounced for GAD than for the peptides, probably related to presence of local GABA neurons in the zona reticulata of the substantia nigra. These results indicate that with the types of lesion used in this study it is not possible to provide evidence for a differential localization within the striatum of dynorphin-, substance P- and GABA-positive cell bodies projecting to the substantia nigra. The radioimmunoassay showed that (Leu)- but not (Met)-enkephalin was affected to the same extent as the dynorphin peptides, supporting the view that (Leu)-enkephalin in the pars reticulata of the substantia nigra is derived from proenkephalin B and not from proenkephalin A. In the immunohistochemical analysis (Met)-enkephalin-like immunoreactivity could only be detected in the pars compacta of the substantia nigra and did not seem to be affected by any of the lesions. The striatal lesions produced a behavioural asymmetry, which could be disclosed by stimulating the rats with apomorphine, which produced ipsilateral rotation.(ABSTRACT TRUNCATED AT 400 WORDS)

Striato-nigral dynorphin and substance P pathways in the rat. II. Functional analysis

In the present study the functional role of the striato-nigral dynorphin and substance P pathways in rat brain has been studied using the rotational behavioural model and an intracerebral dialysis technique complemented with brain lesions and immunohistochemical analysis. Attempts were made to evaluate whether these striato-nigral neurons have a feed-back modulatory action on the dopaminergic nigro-striatal system, or whether they represent an outflow pathway conveying motor information from the striatum. Unilateral injection of dynorphin A into the substantia nigra reticulata of naive rats induced contralateral rotational behaviour. This effect was dose-dependent and mimicked by the kappa-opioid receptor agonist, U50,488H. Intranigral injection of substance P, as well as substance K, also produced dose-dependent contralateral rotational behaviour. Unilateral injections of ibotenic acid into various sites of the striatum were used to destroy the striato-nigral pathways. The lesions produced a depletion of dynorphin- and substance P-like immunoreactivity in the pars reticulata of the substantia nigra ipsilateral to the lesion and markedly affected the behavioural responses to intranigral peptide injections. Dynorphin A more potently induced contralateral rotation in the lesioned compared to naive non-lesioned rats, suggesting development of supersensitivity for this peptide. Substance P on the other hand, was markedly less potent in inducing rotation in lesioned animals. The rotational responses to both dynorphin A and substance P were potentiated by injection of amphetamine 1 h later, suggesting that both peptides act via nigro-striatal dopamine neurons. However, in rats with unilateral nigro-striatal dopamine denervation, produced with 6-hydroxy-dopamine, dynorphin A retained its potency to induce rotational behaviour; substance P was again much less potent. Thus, both the ibotenic acid and 6-hydroxy-dopamine lesions differently affect the action of dynorphin A and substance P in the zona reticulata of the substantia nigra. The data suggests that substance P requires an intact dopamine pathway to produce the rotational response, while dynorphin A does not. Direct evidence that behavioural activation produced by dynorphin A is not dependent upon dopamine stimulation was obtained by intrastriatal dialysis experiments in which changes in striatal dopamine release were measured following intranigral injection of dynorphin A or substance P. Intranigral dynorphin A in fact reduced, while substance P increased the release of dopamine.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunohistochemical demonstration of choline acetyltransferase-immunoreactive preganglionic nerve fibers in guinea pig autonomic ganglia

The distribution of choline acetyltransferase (ChoAcTase)-like immunoreactivity in the superior cervical ganglion and the stellate ganglion was analyzed with immunohistochemistry. A dense network of ChoAcTase-immunoreactive nerve fibers was observed in both ganglia studied. The ChoAcTase-positive fibers were found in all parts of the ganglia but had a differential distribution, giving rise to a patchy staining pattern. After preganglionic denervation of the superior cervical ganglia, all ChoAcTase-positive fibers disappeared. For comparison, the distributions of enkephalin- and neuropeptide Y-like immunoreactivity were analyzed. In the stellate ganglion, the enkephalin-positive fibers had a marked regional distribution. Areas with the highest enkephalin-fiber density seemed to contain low numbers of ChoAcTase-positive fibers and vice versa. The findings give evidence for occurrence of acetylcholine synthesis in preganglionic fibers in paravertebral sympathetic ganglia.

Liquid-phase method for peptide synthesis utilizing photolytic cleavage from a new o-nitrobenzoyl polyethylene glycol support

Photolysis as a method for removal of a tert-butyloxycarbonyl-protected peptide possessing a free C-terminal carboxyl group from a polystyrene support in the solid-phase method of peptide synthesis was introduced by Rich, D. H. and Gurwara, S. K.((1975) J. Am. Chem. Soc. 97, 1575-1578). Using this basic concept we prepared a photosensitive 3-nitro-4-bromomethylbenzoyl polyethylene glycol support for use in the liquid-phase method of peptide synthesis. Photolytic cleavage of a protected tetrapeptide possessing a free C-terminal carboxyl group from the polyethylene glycol support resulted in a 98% yield compared with a 69% yield for the photolytic leavage from the polystyrene support. This application of photolysis as a cleavage method in liquid-phase peptide synthesis avoids the low yields and rather drastic conditons needed to remove a peptide attached directly to the poly-ethylene glycol support in the conventional liquid-phase method.