title: Two actions of gamma-aminobutyric acid on the responses of the isolated basilar artery from the rabbit.
abstract: 1 In the isolated basilar artery of the rabbit, gamma-aminobutyrate acid (GABA) (ED50 +/- s.e. mean, 2.4 +/- 1.1 x 10(-5) M) produced a relaxation, if the tone had been increased with 5-hydroxytryptamine (5-HT). 2 3-Aminoproprane sulphonic acid (3-APS) produced a similar, but smaller relaxation, while baclofen had no effect. The relaxation produced by GABA was inhibited by bicuculline. 3 Transmural electrical stimulation produced a reproducible contraction of the isolated basilar artery. In 9 out 14 preparations GABA (ED50 +/- s.e. mean, 5.6 +/- 2.1 x 10(-7) M) caused a reduction of the response, with a maximum of 49.2 +/- 4.3%. Bicuculline did not inhibit these responses to GABA. 4 Baclofen (ED50 +/- s.e. mean, 6.8 +/- 1.4 x 10(-7) M) produced a similar inhibition (47.4 +/- 3.2% maximum) but 3-APS had no effect. 5 GABA (10(-4) M) had no effect on the tone of isolated mesenteric or internal carotid arteries from the rabbit, whether or not the tone was increased with 5-HT. Similarly, GABA (10(-4) M) did not produce any change in the responses to transmural stimulation in isolated mesenteric or internal carotid arteries. 6 These findings are consistent with the presence of two types of GABA receptor on the rabbit basilar artery.
mesh_terms: D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D001488:Basilar Artery / Q000187:drug effects; D004347:Drug Interactions; D004558:Electric Stimulation; D005260:Female; D018756:GABA Antagonists; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011817:Rabbits; D012701:Serotonin / Q000494:pharmacology; D013654:Taurine / Q000031:analogs & derivatives / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D018756:GABA Antagonists; D013654:Taurine; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; C001355:tramiprosate; D001418:Baclofen