5-Aminovaleric acid interactions with GABAA and GABAB receptors in guinea-pig ileum.
The potential interaction of 5-aminovaleric acid (5-AVA) on GABAA and GABAB receptors was investigated on the guinea-pig isolated ileum myenteric plexus preparation. In the unstimulated preparation 5-AVA (0.1-3 mM) produced a transient contraction which was abolished by previous exposure to picrotoxin (0.1 mM), atropine (3 microM) or tetrodotoxin (0.3 microM). Cross desensitization was observed between the contractile effects of 5-AVA and GABA, while a previous exposure to (+/-)-baclofen did not affect 5-AVA induced contractions. 5-AVA antagonized the relaxant effect of (+/-)-baclofen in unstimulated preparations. 5-AVA (1 mM) had no effect on amplitude of twitches in supramaximally stimulated preparations while GABA produced a concentration related inhibition. In the presence of 5-AVA (1 mM) the concentration response curve to GABA was shifted to the right without a reduction of the maximal effect attainable. These observations indicate that 5-AVA interacts with both GABAA and GABAB receptors in guinea-pig ileum. The concentrations required to observe a GABAA effect are of the same order as those which are effective in producing a blockade of GABAB mediated responses.
Luzzi
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S
Maggi
C A
CA
Spagnesi
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S
Santicioli
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P
Zilletti
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L
D000596:Amino Acids / Q000494:pharmacology*; D021542:Amino Acids, Neutral; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001418:Baclofen / Q000494:pharmacology; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011963:Receptors, GABA-A / Q000187:drug effects*; D013779:Tetrodotoxin / Q000494:pharmacology
D000596:Amino Acids; D021542:Amino Acids, Neutral; D011963:Receptors, GABA-A; D013779:Tetrodotoxin; C013809:5-aminovaleric acid; D001285:Atropine; D001418:Baclofen