异丙酚诱导GAD_(67)-GFP基因敲入小鼠意识消失过程中GABA能神经元的活化

探讨在系统性给予谷氨酸脱羧酶67-绿色荧光蛋白(GAD67-GFP)基因敲入小鼠异丙酚后诱导的意识消失作用中的GA-BA能神经元的活化情况。GAD67-GFP阳性小鼠20只,腹腔注射异丙酚130mg/kg(对照组腹腔注射相同体积的生理盐水)。分别在注射后5min,30min,1h进行行为学评分,随后立即处死并取脑,应用免疫组织化学观察神经元活化标记物Fos在全脑的表达分布并用免疫荧光双标的方法观察Fos与GABA能神经元的共存情况。行为学结果表明在给予异丙酚后5min和30min均能达到适度或深度麻醉效果,而1h时则处于过渡状态,行为学评分为5min时13分,30min时14分,1h时为9分。与对照组相比,Fos在海马CA1区、杏仁核、丘脑室旁核、下丘脑室旁核、梨状核、下丘脑腹内侧核、中脑导水管周围灰质的表达在三个时间点都有明显增加(P<0.05),在嗅球外丛状层有表达但与对照组相比无明显差异(P>0.05)。注射后5min、30min和1h下丘脑腹内侧核有Fos与GABA共存,有共存的细胞占该区域Fos阳性神经元的80.3%、89.7%和91.6%。下丘脑腹内侧核GABA能神经元活化是异丙酚诱导意识消失的可能机制之一。     

GABAergic circuitry in the opossum retina: a GABA release induced by l-aspartate

Glutamate and γ-amino butyric acid (GABA) are the major excitatory and inhibitory neurotransmitters, respectively, in the central nervous system (CNS), including the retina. Although in a number of studies the retinal source of GABA was identified, in several species, as horizontal, amacrine cells and cells in the ganglion cell layer, nothing was described for the opossum retina. Thus, the first goal of this study was to determine the pattern of GABAergic cell expression in the South America opossum retina by using an immunohistochemical approach for GABA and for its synthetic enzyme, glutamic acid decarboxylase (GAD). GABA and GAD immunoreactivity showed a similar cellular pattern by appearing in a few faint horizontal cells, topic and displaced amacrine cells. In an effort to extend the knowledge of the opossum retinal circuitry, the possible influence of glutamatergic inputs in GABAergic cells was also studied. Retinas were stimulated with different glutamatergic agonists and aspartate (Asp), and the GABA remaining in the tissue was detected by immunohistochemical procedures. The exposure of retinas to NMDA and kainate resulted the reduction of the number of GABA immunoreactive topic and displaced amacrine cells. The Asp treatment also resulted in reduction of the number of GABA immunoreactive amacrine cells but, in contrast, the displaced amacrine cells were not affected. Finally, the Asp effect was totally blocked by MK-801. This result suggests that Asp could be indeed a putative neurotransmitter in this non-placental animal by acting on an amacrine cell sub-population of GABA-positive NMDA-sensitive cells.     

GAD isoforms exhibit distinct spatiotemporal expression patterns in the developing mouse lens: correlation with Dlx2 and Dlx5.

Gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter of the adult nervous system and its biosynthetic enzyme glutamic acid decarboxylase (GAD) are abundantly expressed in the embryonic nervous system and are involved in the modulation of cell proliferation, migration, and differentiation. Here we describe for the first time the expression of GABA and embryonic and adult GAD isoforms in the developing mouse lens. We show that the GAD isoforms are sequentially induced with specific spatiotemporal profiles: GAD65 and embryonic GAD isoforms prevail in primary fibers, while GAD67 is the predominant GAD expressed in the postnatal secondary fibers. This pattern correlates well with the expression of Dlx2 and Dlx5, known as upstream regulators of GAD. GABA and GAD are most abundant at the tips of elongating fibers and are absent from organelle-free cells, suggesting their involvement is primarily in shaping of the cytoskeleton during fiber elongation stages.     

GABAergic interneurons and neuropil of the intralaminar thalamus: an immunohistochemical study in the rat and the cat,with notes in the monkey

Summary Immunohistochemistry using antibodies to glutamic acid decarboxylase (GAD) was used to investigate the intralaminar nuclei of the thalamus in rat, cat and monkey. Antibodies to gamma aminobutyric acid (GABA) were also used in the cat. Intralaminar immunoreactive cell bodies were not detected in the rat, but were clearly present in cat and monkey. In the latter species, GABA- or GAD-immunopositive perikarya were distributed throughout the anterior intralaminar nuclei, whereas in the posterior intralaminar complex they prevailed in the lateral part of the centre median nucleus and around the fasciculus retrofiexus. Measurements of the area of immunostained intralaminar cell bodies in cat and monkey indicated that they are represented by small neurons. Experiments in the cat, based on retrograde tracers injections involving large sectors of the frontal and parietal cortices and the head of the caudate nucleus, revealed that the GABA- or GAD-immunoreactive cells and the retrogradely labeled projection neurons represented two separate intralaminar cell populations, although the latter also included small cells. Considerable differences were observed in the immunoreactive GABAergic neuropil of the anterior and posterior intralaminar nuclei. Clusters of densely packed bouton-like immunoreactive elements were detected in the former structures in the rat, cat and monkey, and were especially evident in the central lateral nucleus; immunopositive varicose fibers and puncta were diffusely distributed in the posterior intralaminar structures. Taken together with data from the literature, the present findings indicate that in cat and monkey local circuit inhibitory cells regulate not only the activity of principal thalamic nuclei which project densely upon restricted cortical fields, but also of the intralaminar structures which are widely connected with the cerebral cortex and the striatum. Regional variations in the distribution of GABAergic fibers and terminals suggest major differences in the organization of inhibitory circuits and synaptic arrangements of the anterior and posterior intralaminar thalamus.Abbreviations CeM central medial nucleus - CL central lateral nucleus - CM-Pf centre median-parafascicular complex - fr fasciculus retrofiexus - Hb habenular complex - LD laterodorsal nucleus - LP lateroposterior nucleus - MD mediodorsal nucleus - Pc paracentral nucleus - PO thalamic posterior complex - PvA anterior paraventricular nucleus - Sm stria medullaris - VL ventral lateral nucleus - VP ventroposterior complex     

Neurotrophin receptors expression in the developing mouse retina: an immunohistochemical study

 Neurotrophins and their receptors (p75 and Trk family of receptors) play an important role in the survival of different populations of neurons in the central and peripheral nervous system. Expression of p75, TrkA, TrkB and TrkC was examined in mouse retinas by means immunohistochemistry in the postnatal development of normal and rd/rd mice (C57BL/6J). The rd/rd mice suffer a degeneration that causes a massive lost of photoreceptor cells. Results showed immunoreactivity to all three Trk proteins in both normal and rd/rd mice during the first 21 postnatal days, but some variations in intensity and localization were found. p75 immunoreaction was only present in rd/rd mice at the end of the degeneration process. These results could indicate a role of neurotrophins and their receptors in both the postnatal development of mouse retina and the degeneration process of rd/rd mice. Accepted: 30 October 1996     

Ultrastructural identification of somata and neural processes immunoreactive to antibodies against glutamic acid decarboxylase (GAD) in the dorsal lateral geniculate nucleus of the cat

Summary The cat dorsal lateral geniculate nucleus (LGN) was examined at the light- and electron-microscopic level after immunocytochemistry for GAD (the synthesizing enzyme of the inhibitory neurotransmitter GABA), to identify cells and processes with GAD-like immunoreactivity. GAD-positive perikarya were distributed throughout the A and C laminae, constituting a moderate proportion of cells in the LGN. Labeled cells were characterized by small size, scant cytoplasm, relatively large nuclei with common indentations, small mitochondria, few organelles and few strands of rough endoplasmic reticulum. Unlabeled cells were of large, medium and small size. GAD-positive terminals were identified as F1 and F2 types (Guillery's nomenclature) on the basis of their synaptic relations and ultrastructure. Labeled F2 terminals were postsynaptic to retinal (RLP) boutons and presynaptic to unlabeled dendrites in synaptic glomeruli. Labeled F1 terminals made synapses on unlabeled somata and dendrites, and on labeled dendrites and F2 terminals. Presumably, most labeled F1 terminals originate from GABAergic perigeniculate axons. Retinal (RLP) and cortico-geniculate (RSD) boutons remained unlabeled in the reative zone. These terminals made synapses with labeled and unlabeled dendrites and with labeled F2 boutons. In conjunction with previous studies on GAD-positive cells in the perigeniculate nucleus, these results provide immunocytochemical and morphological evidence suggesting that the GABAergic intrinsic and extrinsic (perigeniculate) interneurons mediate the different inhibitory phenomena which occur in relay cells of the cat LGN. The ultrastructural features and synaptic relations of GABAergic cells and processes in the cat LGN are similar to those of equivalent neural elements in the LGN of rat and monkey, suggesting general principles of organization and morphology for GABAergic neurons in the thalamus of different mammals.Supported in part by grants EY 02877 and HD 03352 from the National Institutes of Health     

Neural elements containing glutamic acid decarboxylase (GAD) in the dorsal lateral geniculate nucleus of the rat; immunohistochemical studies by light and electron microscopy

Immunoreactive constituents of the dorsal lateral geniculate nucleus of adult albino rats were examined by light- and electron-microscopy, using the unlabelled antibody enzyme method, following treatment of brain slices with a purified antibody to glutamic acid decarboxylase. The neuropil of the dorsal lateral geniculate nucleus displayed a conspicuous granular immunoreactivity. In addition, the antibody was bound to a class of small neurons of characteristic morphology. These cells possessed few (commonly 2-4) sparsely branched, long dendrites from some of which immunoreactive appendages were traced. Many cells were bipolar in form, and the dendrites of some appeared to be preferentially orientated. The immunoreactive cells closely resembled intrinsic interneurons characterized in previous Golgi studies of this nucleus. By electron-microscopy, immunoreactive presynaptic elements were present both in the extraglomerular neuropil and in the synaptic glomeruli. The former were axon terminals containing flattened synaptic vesicles and making Gray type II axo-dendritic synaptic contact; they appeared to correspond to axon terminals whose origin in the thalamic reticular nucleus has been established in previous studies, but it is possible that some were axon terminals of intrinsic interneurons. The immunoreactive glomerular components also contained flattened vesicles, were presynaptic to presumptive projection cell dendrites, postsynaptic to retinal axon terminals, and participated in triplet (triadic) and other complex synaptic arrangements. They corresponded in all respects to the synaptic portions of the complex dendritic appendages of intrinsic interneurons, identified and characterized in previous studies. The finding that there are high levels of glutamic acid decarboxylase in the cell bodies, dendritic shafts and dendritic appendages of intrinsic interneurons in the dorsal lateral geniculate nucleus of the rat, and in the axon terminals of fibres projecting to this site from the thalamic reticular nucleus, allows us to conclude that the inhibitory inputs to the geniculo-cortical projection cells from both of these sources are probably mediated by gamma-aminobutyric acid.     

Chromogranin A in gastric neuroendocrine tumours: an immunohistochemical and biochemical study with region-specific antibodies

The aim of the present study was to investigate ECLomas and enterochromaffin-like (ECL) cell hyperplasia in gastric human mucosa regarding the immunohistochemical expression of chromogranin A (CgA) epitopes and to measure the same CgA epitopes in plasma samples. Eight gastric biopsies from ECLomas, seven of type I and one of type III, and biopsies from one patient showing only ECL cell hyperplasia were included in the study. Our results revealed a varying expression of region-specific CgA epitopes in the ECLomas regarding both the frequency of immunoreactive cells and intensity of immunoreactivity. CgA284–301 (pancreastatin) was not revealed in any neoplasm, whereas CgA361–372 (catestatin) was expressed in all ECLomas. However, the number of immunoreactive cells to vesicular monoamino transporter 2 (VMAT 2) or the commercial monoclonal CgA (CgA250–284) antibodies were generally higher. The plasma concentrations of the region-specific CgA radioimmunoassays differed considerably, with highest concentrations of CgA1–17 and CgA116–130 epitopes and the lowest with the CgA17–37, CgA63–76, CgA238–247 and CgA441–424 epitopes. No relationship was found between tissue expression and plasma concentration of CgA epitopes. In conclusion, this study shows that VMAT 2 and the commercial CgA antibodies seem more useful for histopathological diagnosis of ECLomas than the antibodies to the other CgA regions.     

GABAergic inhibition in the rat pontine nuclei is exclusively extrinsic: evidence from an in situ hybridization study for GAD67 mRNA

 As clearly indicated by our electrophysiological work, GABAergic inhibition plays a powerful role in the pontine nuclei (PN), the major link between cerebral cortex and the cerebellum. Using the technique of in situ hybridization for the mRNA encoding for the γ-aminobutyric acid (GABA)-synthesizing isoenzyme glutamic acid decarboxylase₆₇ (GAD₆₇), we demonstrate here the total absence of potentially GABAergic neurons from the rat PN. This negative finding supports the notion that GABAergic inhibition in the PN of rats, unlike that of higher mammals, is exclusively based on extrapontine GABAergic afferents. Received: 20 August 1998 / Accepted: 29 October 1998     

Differentiation and development of human female germ cells during prenatal gonadogenesis: an immunohistochemical study

BACKGROUND: In the development of the human ovary, the second trimester includes the transition from oogonial replication to primordial follicle formation. The present study was carried out to assess differentiation and proliferation of germ cells in a series of female gonads from 19 fetuses from the second and third trimester, and two neonates. METHODS: Using immunohistochemistry, the following markers were studied: placental/germ-like cell alkaline phosphatases (PLAP), the marker of pluripotency OCT3/4, the proliferation marker Ki-67, beta-catenin and E-cadherin, the stem cell factor receptor c-KIT, and VASA, a protein specific for the germ cell lineage. RESULTS: PLAP and OCT3/4 were seen during oogenesis, but not in germ cells engaged in folliculogenesis. A similar pattern was observed for Ki-67. Loss of pluripotency occurs once oocytes engage in follicle formation, suggesting a role of cell-cell interactions in the process of germ cell maturation. VASA, c-KIT, beta-catenin and E-cadherin were found in germ cells at all developmental stages of oogenesis and folliculogenesis. CONCLUSIONS: Immunohistochemically, two groups of germ cells can be distinguished. Germ cells that are predominantly found in the cortical region of the ovary before weeks 22-24 of gestation, showing an immature phenotype, are mitotically active, and express OCT3/4, a marker of pluripotency. On the other hand, germ cells undergoing folliculogenesis have lost their pluripotent potential and no longer proliferate.     

Tumour responding accessory cells in testicular seminoma: an immunohistochemical study

AIM: To investigate the role of accessory cells (and other chronic inflammatory cells) in the host immune response to testicular seminoma by defining their immunophenotypic characteristics and topographical arrangement. METHODS AND RESULTS: A panel of antibodies applicable to paraffin-embedded tissues was employed to characterize the host chronic inflammatory response in eight cases of classical testicular seminoma. The antibodies were directed against CD45RO, CD20, CD68, acid cysteine proteinase inhibitor (ACPI), MAC387, muramidase (MUR), S100 protein, Factor XIIIa, CD21 and HLA Class II. In all cases the majority of the inflammatory cells were T-lymphocytes situated mainly in areas of apparent tumour destruction. Large numbers of macrophages/dendritic cells which had not been evident by conventional light microscopy were also demonstrated. In particular, an immunophenotypically distinct population of accessory cells showing a specific pattern of distribution was revealed. It clearly rimmed islands of tumour and showed strong positive staining for CD68, MAC387 and HLA Class II. CONCLUSION: The study has identified an immunophenotypically distinct population of accessory cells showing a characteristic topographical arrangement. It is proposed that it represents a subpopulation of macrophages which are responding directly to the tumour and are likely to play a part in influencing tumour dynamics.     

Evidence for the presence of a histaminergic neuron system in the rat brain: an immunohistochemical analysis

The binding of calcium antagonists in the rat hippocampal formation was studied using autoradiography. Hippocampal slices were labeled in vitro with [3H]PN 200-110. High densities of binding sites for calcium antagonists were found in the molecular layer of the dentate gyrus and in the CA3 subfield of the hippocampus. After ablation of the granule cells by local injection of colchicine a marked decrease in the number of [3H]PN 200-110 binding sites density was observed on these areas, while binding to other parts of the hippocampal formation and brain was spared. These results strongly suggest the localization of high densities of calcium channels to the granule cells of the dentate gyrus.     

The distribution and cellular localization of glutamic acid decarboxylase-65 (GAD65) mRNA in the forebrain and midbrain of domestic chick

The distribution and cellular localization of GAD65 mRNA in the forebrain and midbrain of domestic chick were examined by in situ hybridization histochemistry with ³⁵[S]-UTP labeled cRNA probes, using film and emulsion autoradiography. Film autoradiograms showed intense GAD65 labeling in many structures of the basal telencephalon, such as the medial and lateral striatum, the septum, the olfactory tubercle, the lateral bed nucleus of the stria terminalis, and the intrapeduncular nucleus, while the pallial telencephalon showed only a low level of labeling. Emulsion-coated sections revealed that GAD65 mRNA-containing neurons were at least six times more abundant in striatum than pallium, with only a uniformly scattered subpopulation labeled in pallium, and that the vast majority of the large scattered projection neurons of globus pallidus were heavily labeled for GAD65. Prominent labeling was also evident in the nucleus taeniae and subpallial amygdala, but not in the arcopallium in film autoradiograms. Within the diencephalon, the hypothalamus was more GAD65-rich than the thalamus. Additional subtelencephalic cell groups showing prominent labeling included the thalamic reticular nucleus and ventral lateral geniculate nucleus of the diencephalon, the nucleus pretectalis, subpretectalis and spiriformis lateralis of the pretectum, and the magnocellular isthmic nucleus of the optic lobe. Tectal layers 9–10 were also rich in GAD65. These results further clarify GABAergic circuits of the avian forebrain and midbrain, and show them to closely resemble those in mammals.     

Immunocytochemical evidence suggests that taurine is colocalized with GABA in the Purkinje cell terminals,but that the stellate cell terminals predominantly contain GABA: a light- and electronmicroscopic study of the rat cerebellum

Summary The distributions of taurine-like and GABA-like immunoreactivities in the rat cerebellum were compared by analysis of consecutive semithin and ultrathin sections, postembedding labeled with the peroxidase-antiperoxidase technique or with an indirect immunogold procedure, respectively. Taurine-like immunoreactivity was selectively enriched in Purkinje cell bodies, dendrites and spines, and boutons in the cerebellar nuclei exhibiting ultrastructural features typical of Purkinje cell terminals. The stellate and basket cell bodies and terminals were very weakly labeled. A computer assisted quantitative assessment of the net immunogold labeling revealed that the mean gold particle density in the Purkinje cell terminals was about 70% higher than that in the Purkinje cell dendrites, and about 14 times higher than that in the stellate/basket cell terminals in the molecular layer. Stellate, basket and Purkinje cell terminals emerged as intensely immunoreactive in adjacent sections processed with an antiserum against conjugated GABA. These findings indicate, contrary to recent electrophysiological data, that GABA is a more likely transmitter candidate than taurine in the stellate cells. The apparent colocalization of GABA and taurine in the terminals of Purkinje cells raises the possibility that these terminals are capable of releasing two different inhibitory amino acids.     

Doublecortin expression continues into adulthood in horizontal cells in the rat retina

The doublecortin (DCX) protein is associated with microtubules, and is essential for neuronal migration, differentiation, and plasticity. In mammals, it is expressed in developing neurons and new immature neuroblasts in the adult brain, but not generally in mature neurons. In the retina, doublecortin is detectable as early as embryonic day 15 (E15), is highly expressed between E18 and E20, and is poorly expressed postnatally. In this study, we investigated immunohistochemically the expression and cellular localization of doublecortin in the adult rat retina. Doublecortin was expressed in the outer plexiform layer (OPL), and in cells in the outer border of the inner nuclear layer (INL). No other layers were labeled by anti-doublecortin antibodies. In double-labeling experiments, doublecortin expression co-localized with the expression of the marker for horizontal cells, calbindin D. By contrast, the marker for immature neuroblasts, polysialylated neural cell-adhesion molecule, was not expressed in horizontal cells. These results suggest that either horizontal cells have the capacity to continuously remodel their neurites or doublecortin has a different function in horizontal cells from the control of neuronal plasticity that it is known to modulate other neurites. In addition, doublecortin might be an alternative molecular marker for horizontal cells in the adult rat retina.     

Early development of chick embryo respiratory nervous system: an immunohistochemical study

The extrinsic and intrinsic respiratory nervous systems receive specific contributions from the vagal and sympathetic components. Using specific markers for vagal and sympathetic structures, we studied the distribution patterns of immunoreactivity to galanin (GAL), pituitary adenylate cyclase-activating polypeptide-27 (PACAP) and the tachykinin substance P in extrinsic and intrinsic nerve of chick embryo respiratory system, during development from the very early age to hatching. All peptides studied appeared in the intrinsic and extrinsic nervous systems early. We found substance P in both the vagal and sympathetic systems, PACAP in vagal components alone and GAL mainly in the sympathetic system. The intrinsic nervous system showed high immunoreactivity for all peptides studied. These data accord with the well known early trophic functions that peptides have on the development of nervous networks and modulatory activity on the intrinsic nervous system. The GAL again proves to be the main peptide in chick embryo sympathetic respiratory system.     

Regional density of monoamine-accumulating amacrine cells in the rabbit retina

The spatial distribution of noradrenaline (NA)- and indoleamine-accumulating (IA) amacrine cells was studied by fluorescence microscopy in flatmounts and tangential cryosections (15 μm thickness) of albino rabbit retinas. The two classes of cells were found to be distributed over the retinal field in a mixed and random fashion. The regional density (mean ± S.D. cells/mm²) of monoamine-accumulating cells was highest in the visual streak (NA cells, 88 ± 5; IA cells, 1507 ± 92), and lowest (41 ± 7; 625 ± 105, respectively) in the inferior periphery. The density ratio of NA:IA cells was 1:15 on average. Among cells located in the amacrine cell layer, NA and IA cells accounted for 0.3 and 3.9% of the total cell population, respectively. Monoamine-accumulating amacrine cells displaced into the ganglion cell layer were few; these displaced cells were only 2% and 0.6% of the cell number of normally situated cells in the amacrine cell layer for NA and IA cells, respectively.     

Light- and electron-microscopic immunocytochemistry of glutamic acid decarboxylase (GAD) in the basal hypothalamus: Morphological evidence for neuroendocrine γ -aminobutyrate (GABA)

GABAergic cells and axon terminals were localized in the basal hypothalamus of different species (rat, mouse and cat), by means of an immunocytochemical approach using a specific and well-characterized antiserum to the GABA biosynthetic enzyme, glutamate decarboxylase. Lightmicroscopic visualization was performed with an indirect immunofluorescence method and electron-microscopic observations were made on material with pre-embedding staining and use of the peroxidase-antiperoxidase procedure.At the light-microscopic level, a dense immunofluorescent plexus was observed over both the medial and lateral parts of the external layer of the median eminence. The labelling extended from the rostral part of the median eminence up to the pituitary stalk. Over the subependymal and internal layers only a few immunoreactive dots were visible, except around the blood vessels where they appeared more concentrated. Immunoreactive varicosities could be found following the outlines of the capillary loops and lining tanycyte processes, especially in the median eminance midportion.At the electron-microscopic level, the immunolabelling was exclusively found over neuronal profiles in the median eminence. The latter represented a small fraction of the total number of varicosities visible on the same section. Labelled profiles typically contained numerous small clear synaptic vesicles and only a few or no dense-core vesicles. In the subependymal and internal layers, rare labelled endings were found close to ependymal cells or among transversally cut fibers, respectively. In the palisadic zone, elongated positive boutons were visible intermingled with bundles of unlabelled axons and glial or ependymal processes. In the neurohemal contact zone, immunoreactive endings were observed among unlabelled neurosecretory endings in close vicinity to fenestrated capillary perivascular space.Small moderately intense immunofluorescent varicosities were observed all over the hypothalamus. The density of the glutamate decarboxylase-positive network was higher than in most diencephalic regions. Intraventricular or topical injection of colchicine allowed the visualization of small lightly immunoreactive cells in the diffusion area of colchicine. In the arcuate nucleus labelled axonal endings containing small pleomorphic synaptic vesicles and sometimes a few dense-core vesicles were observed at the electron-microscopic level. Typical synaptic junctions were commonly found between positive endings and unlabelled perikarya, or more frequently, unlabelled dendrites.These findings show that glutamate decarboxylase-containing endings are localized in several strategic sites for potential GABAergic neuroendocrine regulations. The GABAergic endings found among neurosecretory endings in the neurohemal contact zone may provide the morphological support for the release of γ -aminobutyrate into the portal blood flow as an hypothalamic hypophysiotropic hormone. Alternatively, neurosecretory cells might be under GABAergic control expressed either at their terminal level within the median eminence or the cell body level within the parvicellular hypothalamic nuclei.