Peripheral administration of picrotoxin and bicuculline stimulates in vivo somatostatin release from rat median eminence.
The gamma-Aminobutyric acid-A (GABAA) antagonist picrotoxin and bicuculline were administered to male rats to determine their effects on somatostatin (SRIF) release, measured in unanesthetized animals stereotaxically implanted with push-pull cannula in the median eminence (ME). I.p. injection (3 mg/kg) of picrotoxin (n = 5) or bicuculline (n = 6) significantly increased (35.4 +/- 10.8 vs 13.7 +/- 4.3 pg/15 min; P less than 0.03 and 38 +/- 3.5 vs 14 +/- 1.8 pg/15 min; P less than 0.001, respectively) SRIF release from the ME compared to baseline levels measured in the same animals. In contrast, with local perfusion of picrotoxin, (10(-4) to 10(-6) M) SRIF release from the ME was not affected. These data suggest a physiological endogenous inhibitory tone of GABA on SRIF release.
Arancibia
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S
Laboratory of Endocrinological Neurobiology, URA 1197 of CNRS, University of Montpellier II, France.
Briozzo
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P
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007274:Injections, Intraperitoneal; D008297:Male; D008473:Median Eminence / Q000187:drug effects / Q000378:metabolism*; D010852:Picrotoxin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000502:physiology*
D001640:Bicuculline; D010852:Picrotoxin; D013004:Somatostatin; D005680:gamma-Aminobutyric Acid