Effect of .GAMMA.-aminobutyric acid on excitability of tubero-infundibular neurons in rat hypothalamic slices.

Nishihara, Masugi; Kimura, Fukuko; Kawakami, Michiyuki

doi:10.1507/endocrj1954.30.311

Cited by 7 publications

(2 citation statements)

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“…We believe that the method, reported here, for estimation of in vitro activity of TIDA neurons is a useful means for studying the regulatory mechanisms of neurosecretory activity of TIDA neurons. Furthermore, it would become possible to compare and correlate changes in the neurosecretory activity of TIDA neurons with those in the neuronal excitability [32] using in vitro hypothalamic slices.…”

Section: Discussionmentioning

confidence: 99%

Estimation of in vitro Activity of Tuberoinfundibular Dopaminergic Neurons by Measurement of DOPA Synthesis in the Median Eminence of Hypothalamic Slices

Ai¹,

Kimura²

1984

Neuroendocrinology

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A new method for estimation of in vitro neurosecretory activity of tuberoinfundibular dopaminergic (TIDA) neurons was developed by measuring the rate of synthesis of dihydroxyphenylalanine (DOPA) in the median eminence of hypothalamic slices. Sagittal hypothalamic slices of ovariectomized rats were incubated in a medium containing 3-hydroxybenzylhydrazine (NSD 1015), an inhibitor of DOPA decarboxylase. DOPA accumulated in the median eminence following incubation with NSD 1015 was determined by high-performance liquid chromatography with electrochemical detection. The amount of DOPA accumulated in vitro in the median eminence was maximal in a medium containing 10 mM NSD 1015 and linear up to 120 min at 37°C. Increasing the concentration of tyrosinein medium stimulated the synthesis of DOPA in the median eminence. The synthesis of DOPA was blocked by 1 mM α-methyltyrosine, an inhibitor of tyrosine hydroxylase. The rate of in vitro synthesis of DOPA in the median eminence was 33% of that of in vivo synthesis. Incubation in a medium containing 50 mM K⁺ to depolarize neurons caused a 2.4-fold increase in DOPA synthesis in the median eminence. The high K⁺-induced increase in DOPA synthesis was blocked by omission of Ca²⁺ and addition of 1 mM EGTA into the medium, suggesting Ca²⁺ dependency of depolarization-activated DOPA synthesis. These results indicate that this in vitro assay is a useful means to study the regulatory mechanisms of TIDA neurons.

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Section: Discussionmentioning

confidence: 99%

Estimation of in vitro Activity of Tuberoinfundibular Dopaminergic Neurons by Measurement of DOPA Synthesis in the Median Eminence of Hypothalamic Slices

Ai¹,

Kimura²

1984

Neuroendocrinology

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“…The effects of estrogen treatments on the responsiveness of ARC neurons to these agents were also examined, since it has been shown that electrical activity of ARC neurons is affected by estrogen (MAGI, 1973) and that estronge implantation in the ARC causes a change in hormone secretion from the anterior pituitary (AKEMA et al, 1983). A preliminary report of a portion of this study has already been presented (NISHIHARA et al, 1983).…”

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confidence: 99%

Responses of arcuate neurons to some putative neurotransmitters in perfused rat hypothalamic slices : Effects of in vivo and in vitro estrogen treatments.

Nishihara¹,

Matsukawa

Kimura³

1986

Jpn.J.Physiol

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The responses of neurons in the arcuate nucleus (ARC) to yaminobutyric acid (GABA), glycine, serotonin (5-HT), norepinephrine (NE), and dopamine (DA) were examined in hypothalamic slices from ovariectomized rats either treated or untreated with estrogen. In estrogenuntreated preparations, spontaneous unit activity of the majority of neurons identified antidromically by the median eminence (ME) stimulation was depressed by GABA and glycine. When effective, 5-HT was predominantly excitatory and DA was predominantly inhibitory, while NE evoked both excitatory and inhibitory responses. The IS-SD block in evoked spikes was also occasionally observed following GABA and glycine perfusion. The responsiveness of unidentified neurons, which were not activated by the ME stimulation, to agents other than 5-HT did not differ from that of antidromically identified neurons. Responses of unidentified neurons to 5-HT were predominantly inhibitory. Subcutaneous injection of 20,ug of 17/3-estradiol-benzoate 2 days prior to the experiments did not significantly affect the responsiveness of both identified and unidentified neurons to GABA, 5-HT, DA, and NE. Contrarily, preincubation of slices in 17/3-estradiol-containing medium (10 nM) for 1 h significantly increased the responsiveness of unidentified, but not identified, neurons to the inhibitory action of NE. These results suggest that GABA, glycine, 5-HT, NE, and DA play some functional roles in controlling the excitability of tuberoinfundibular (TI) neurons in the ARC. It is also suggested that the negative feedback effect of estrogen is mediated, at least in part, by increased responsiveness of ARC neurons other than TI neurons to the inhibitory action of NE.

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Dimorphic distribution of the two main GABAA binding sites in cortical and limbic areas of a rodent living in natural environmental conditions

1997

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Labeling of the two more important gamma-aminobutyric acidA (GABA(A)) supramolecular sites with [3H] muscimol (GABA(A)) and [3H] flunitrazepam (benzodiazepine) provided saturable, stable, and dimorphic binding activities in cortical and limbic regions of the wood mouse Apodemus sylvaticus. Of the cortical layers, which contained the highest [3H] muscimol binding levels, only the female lamina V supplied a greater (51%; P <0.01) receptor density than in the male. Areas of the limbic system instead proved to be the more favorable targets for differential GABA(A) binding levels. The highest (P <0.001) and higher levels were found in the oriens-pyramidalis CA1 layer of the hippocampus (65%) and in the vertical limb diagonal band-medial septal nucleus (48%), basolateral amygdala nucleus (45%), and ventromedial hypothalamic nucleus (43%), respectively, of the female. A similar pattern was obtained for [3H]flunitrazepam binding activity, especially in the presence of GABA. The highest and higher binding activities were obtained in the female central amygdala nucleus (78%) and in the ventromedial hypothalamic nucleus (52%), basolateral amygdala nucleus (48%), and oriens-pyramidalis CA1 layer of the hippocampus (47%), respectively, whereas higher levels were observed only in the male vertical limb diagonal band-medial septal nucleus (56%). Even in the cortical regions, the female exhibited higher (42%; cortex lamina V) and moderately higher (38%; cortex lamina VI) levels, with binding differences in the latter site plus in the basolateral amygdala nucleus occurring in a GABA-nondependent manner. From the saturation binding analyses it was possible to reveal that both maximal number of binding sites (Bmax) and mean dissociation constant (K(D)) modifications were responsible for receptor differences of the two GABAergic sites. These findings tend to suggest that dimorphic variations of the GABA(A) supramolecular sites, in some cortical and limbic regions, are strongly involved in sex-specific aggressive and reproductive activities of rodents living in their natural habitats.

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Effect of .GAMMA.-aminobutyric acid on excitability of tubero-infundibular neurons in rat hypothalamic slices.

Abstract: The effect of ƒÁ

Cited by 7 publications

References 30 publications

Estimation of in vitro Activity of Tuberoinfundibular Dopaminergic Neurons by Measurement of DOPA Synthesis in the Median Eminence of Hypothalamic Slices

Estimation of in vitro Activity of Tuberoinfundibular Dopaminergic Neurons by Measurement of DOPA Synthesis in the Median Eminence of Hypothalamic Slices

Responses of arcuate neurons to some putative neurotransmitters in perfused rat hypothalamic slices : Effects of in vivo and in vitro estrogen treatments.

Dimorphic distribution of the two main GABAA binding sites in cortical and limbic areas of a rodent living in natural environmental conditions

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