Presynaptic actions of GABA and baclofen in CA1 region of the guinea-pig hippocampusin vitro

Morishita, Wade; Sastry, B.R.

doi:10.1016/0306-4522(94)90425-1

Cited by 7 publications

(1 citation statement)

References 39 publications

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“…However, a substantial sup pression of the field response was consistently elicited at higher doses. These electrophysiologic observations are consistent with previous reports of complex effects of GABAB receptor activation on neuronal responses (Dav ies et aI., 1990;Steffensen and Henriksen, 1991;Otis and Mody, 1992;Morishita and Sastry, 1994).…”

Section: Resultssupporting

confidence: 82%

GABAergic Regulation of Cerebral Microvascular Tone in the Rat

Fergus

Lee

1997

J Cereb Blood Flow Metab

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Summary:The role of GABA in regulating cerebral mi crovessels was examined in the parenchyma of the hippocam pus and the surface of the neocortex. Microvessels were moni tored in in vitro slices using computer-assisted videomicros copy, and synaptically evoked field responses were simultaneously recorded. ,/-Aminobutyric acid (GAB A) and the GABAA receptor agonist, muscimol, elicited vasodilation in hippocampal microvessels, whereas the GABAB receptor agonist, badofen, elicited constriction. The muscimol-induced dilation persisted in the presence of the nitric oxide synthase inhibitor, N-nitro-L-arginine, indicating that this response is not mediated by nitric oxide. Inhibition of neuronal discharge ac tivity with tetrodotoxin did not alter this dilation, but it fully blocked the constrictor response to baclofen. These data sug gest that GABAB-mediated, but not GABAA-mediated, re sponses are dependent on action potential generation. The GABAA receptor antagonists, bicuculline and picrotoxin, elicConverging lines of evidence suggest that local neu rons are major participants in the regulation of regional cerebral blood flow (CBF). At rest, regional CBF is di rectly correlated with the level of local neuronal activity (Lou et aI., 1987). Furthermore, CBF increases in a spa tially and temporally precise manner during enhanced neuronal activity (Fox and Raichle, 1986). This vascular response frequently is dissociated from changes in re gional cerebral metabolism, suggesting that these blood flow changes are not necessarily a consequence of meta bolic alterations (Lenniger-Follert and Lubbers, 1976; Nakai et a!., 1983; Fox and Raichle, 1986; Lou et aI., 992ited constriction, suggesting a tonic dilatory influence by en dogenous GABA. Bicuculline-induced constriction was not at tenuated by tetrodotoxin. In contrast, these vessels were unre sponsive to the GABAB receptor antagonist, 2-hydroxysac lofen. Hippocampal microvessels dilated in response to mod erate hypoxia, and this response persisted in the presence of bicuculline, indicating that the hypoxia-induced dilation is not mediated by an action at GABAA receptors. In arterioles lo cated on the surface of the neocortex (i.e., not embedded in the parenchyma of the brain), muscimol elicited vasodilation, whereas bicuculline was ineffective. These results suggest that although these vessels are responsive to GABA, the local con centration of endogenous GABA is insufficient to elicit a tonic effect at rest. These findings raise the possibility that GABA plays a role in local neurovascular signaling in the parenchyma of the brain.

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Section: Resultssupporting

confidence: 82%