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M Tappaz

Publications and source records attributed to M Tappaz.

48 records · Page 3Linked to original sources
PubMed1986

Endocrine modulation of gamma-aminobutyric acidergic innervation in the rat fallopian tube.

The present study investigates the effect of different endocrine manipulations on the gamma-aminobutyric acid (GABA)-ergic system in the rat fallopian tube. Either hypophysectomy or ovariectomy induced a significant decrease of glutamic acid decarboxylase (GAD) activity and of GABA levels in in situ tubes. This effect was completely reversed by either gonadotropins or combined estrogen-progesterone administration, respectively. Estrogen or progesterone alone proved less effective than the administration of both steroids in counteracting the effect of ovariectomy on GAD activity. The in vitro incubation of ovariectomized rat fallopian tubes with estrogen-progesterone for 1 h failed to counteract the reduction of the GAd activity induced by surgical manipulation. The in vivo effect of estrogen-progesterone administration on the GABA-ergic system seems to be specific since steroid treatment induced the synthesis of an enzyme which was immunologically identical to the GAD present in the fallopian tube and brain of normal diestrous rat. Autotransplantation of the fallopian tube under the skin brought about a decrease of GAD activity similar to that obtained after ovariectomy. In this situation, however, estrogen-progesterone administration did not counteract the decrease of GAD activity induced by fallopian tube deafferentation. The present results demonstrate that an interaction between the GABA-ergic system and the hypothalamo-pituitary-gonadal axis seems to be operative at the level of the rat fallopian tube. However, the physiological meaning of this interrelationship between the endocrine and the peripheral nervous systems remains to be clarified.

Animals↗
PubMed1985

Opposite effects of monosodium glutamate on the dopaminergic and GABAergic innervations of the median eminence and the intermediate lobe in the mouse.

In the mouse, monosodium glutamate (MSG) administered neonatally provokes the necrosis of most dopaminergic perikarya in the arcuate nucleus, as classically described, but also stimulates surviving neurons as shown by their increase in both size and immunoreactivity for tyrosine hydroxylase (TH). In the treated animals, TH-immunoreactive axons rarefy in the median eminence (ME) external zone, but postnatal dopaminergic innervation of the intermediate lobe (IL) normally develops and even, due to enlarged axonal varicosities, is more conspicuous than in the control littermate IL at same stages. gamma-Aminobutyric acid-ergic (GABAergic) projections in the ME and the IL, revealed with a glutamic acid decarboxylase antiserum, have the same distribution as TH-immunoreactive axons and present the same modifications in the MSG-treated animals. No clearcut differences in dopaminergic and GABAergic innervation patterns can be observed in the IL in treated and control adult mice.

Animals↗
PubMed1984

Catecholaminergic and GABAergic anatomical relationship in the rat substantia nigra, locus coeruleus, and hypothalamic median eminence: immunocytochemical visualization of biosynthetic enzymes on serial semithin plastic-embedded sections.

The visualization of protein antigens has been performed on semithin sections embedded in Araldite. After partial removal of the resin and a light proteolytic treatment of the tissue we were able to localize several biosynthetic enzymes: tyrosine hydroxylase (TH), phenylethanolamine N-methyltransferase (PNMT), and glutamic acid decarboxylase (GAD), which are, respectively, markers of catecholaminergic, adrenergic, gamma-aminobutyric acid (GABA)ergic systems. This technique afforded a high resolution of light microscopy details and immunostaining of TH, GAD, and PNMT on serial sections enabled us to compare with great precision GABAergic and adrenergic innervations in the rat locus coeruleus. In addition, it allows us to study the possible relationship between these terminals and the noradrenergic neurons. We also compared the general pattern of distribution of TH- and GAD-positive endings in the hypothalamic median eminence. The preliminary results obtained with this technique revealed some interesting facts previously unseen when preparations with lower histological resolution were used.

Animals↗
PubMed1980

Evidence for the presence of melatonin in the human brain.

Melatonin was measured by radioimmunoassay in human brain and pineal gland. Levels were 50 times lower in brain than in pineal. The distribution appeared uneven between the various areas studied. No measurable hydroxyindol-O-methyltransferase activity could be shown. These findings suggest that what appears to be melatonin in the human brain is unlikely to be synthesized in situ.

Acetylserotonin O-Methyltransferase↗
PubMed1980

Autoradiography of GABA in the rat hypothalamic median eminence.

Light microscopy autoradiographs of the rat hypothalamic median eminence were prepared after injection of high specific activity tritiated GABA and GABA structural analogs. Following intracardiac injection of labeled GABA with short (15 min) survival time, a dense accumulation of silver grains was observed over the external layer of the median eminence. The silver grains appeared much less numerous and randomly scattered over the internal layer. No conspicuously labeled cells could be detected in the median eminence. A similar pattern of labeling was observed after 10 min in vitro incubation of the median eminence with a low concentration (2.5 x 10(-7) M) of labeled GABA. Clusters of silver grains were also visible over the external layer following intraventricular injection of labeled GABA. In this latter case, however, other sites of labeling were revealed over the internal and ependymal layers. The dense labeling over the external layer with tritiated GABA was partially reduced by a simultaneous intracardiac injection of a 50-fold excess of non-radioactive cis-aminocyclohexane carboxylic acid--a reported preferential substrate for GABA neuronal uptake--but it was not displaced by a 2000-fold excess of non-radioactive beta-alanine--a reported specific substrate for GABA glial uptake. Intracardiac injection of triated beta-alanine led to a faint and even labeling over the entire median eminence with no preferential accumulation of silver grains over the various layers. Following intraventricular injection of labeled beta-alanine the tanycytes and their processes as well as numerous glial cells appeared heavily labeled. These results suggested that there exist cell elements in the external layer of the hypothalamic median eminence which are capable of accumulating exogenous GABA according to its neuronal uptake characteristics. Although the exact nature of these cells is not readily apparent at this stage of our investigations, these findings led us to speculate that there might be a subpopulation of GABAergic nerve endings in the vicinity of the primary plexus capillaries.

Alanine↗
PubMed1979

GABA-accumulating neurons in the nucleus raphe dorsalis and periaqueductal gray in the rat: a biochemical and radioautographic study.

The possibility of a GABAergic innervation of the nucleus raphe dorsalis (NRD) has been investigated by using the following approaches: (i) the identification of the principal neuronal groups afferent to the NDR by using horseradish peroxidase retrograde transport, (ii) the determination of glutamate decarboxylase activity (GAD) in the NRD after lesioning these groups or their putative pathways, and (iii) the radioautographic identification of terminals axons and nerve cells accumulating intraventricularly injected [3H]GABA. The hypothesis of a local GABAergic network is supported by the failure to obtain important changes in GAD after lesions of NRD afferents and the presence in this nucleus of terminals, fibers and nerve cell bodies accumulating [3H]GABA. It appears that these GABA-accumulating neurons could represent a portion of aperiventricular GABAergic system in the periaqueductal gray and the pontine ventricular gray.

Afferent Pathways↗
PubMed1978

[Identification of GABA accumulating neurons in the dorsal raphe nucleus].

A possible GABAergic innervation of the nucleus raphe dorsalis (NRD) was investigated by measuring glutamate decarboxylase activity in the NRD after lesioning the afferents of this nucleus. The slight decrease found in the enzymatic activity suggests that these afferents have a minor participation in the GABA innervation of the NRD and implies the existence of an intrinsic GABAergic system in this nucleus. This local innervation was demonstrated by radio-autography and shows fibers, axonal varicosities and cell bodies which accumulate 3H GABA in the caudal part of this nucleus.

Animals↗
PubMed1976

Distribution of releasing factors, biogenic amines, and related enzymes in the bovine median eminence.

The bovine median eminence was dissected into eight different subdivisions: rostral, anterior internal, anterior external, middle external medial, middle external lateral, middle internal medial, middle internal lateral, and caudal. Thyrotropin-releasing hormone (TRH) was found in the highest concentrations in the middle external medial and lateral subdivisions; luteinizing hormone-releasing hormone (LHRH) was concentrated in the middle external lateral and anterior internal subdivisions. Among the various neurotransmitters and enzymes assayed, only dopamine and choline acetyltransferase were present in highest concentrations in the same subdivisions of the bovine median eminence found to be rich in TRH and LHRH. The distributions of norepinephrine, dopamine-beta-hydroxylase, serotonin, tryptophan hydroxylase, phenylethanolamine-N-methyltransferase, glutamic acid decarboxylase, and histamine appeared to correlate poorly with the major distributions of TRH and LHRH. These findings suggest that at the level of the median eminence, central neuroendocrine regulation of TRH and LHRH release may involve an interaction only with dopamine and acetylcholine.

Animals↗