title: GABA-related activities of amino phosphonic acids on guinea-pig ileum longitudinal muscle.
abstract: The effects of phosphonic analogues of GABA, beta-alanine and glycine on guinea-pig ileum longitudinal muscle were measured. Aminomethylphosphonic acid (AMPh) and 2-aminoethylphosphonic acid (2-AEPh) were devoid of any effect both in non-stimulated preparations and in electrically-stimulated preparations. The phosphonic analogue of GABA, 3-aminopropylphosphonic acid (3-APPh) possessed a GABAB agonistic effect (relaxation and inhibition of twitch response) at doses of 10(-3)M. No agonistic effect on GABAA receptors was observed. 3-APPh at doses tested (2 X 10(-4)M and 10(-3)M) also displayed antagonistic action on the effects of GABAB agonists producing a parallel shift of the log dose-effect curves of GABA- and (-)-baclofen-inhibition of twitch responses. In contrast 3-APPh did not antagonize the inhibitory effect of morphine and noradrenaline. The contractile effect of GABA, mediated via GABAA receptors, was unaffected by 3-APPh(10(-3)M). It is concluded that 3-APPh is a partial agonist at the GABAB site in guinea-pig ileum.
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D063065:Organophosphonates / Q000494:pharmacology*; D011437:Propylamines / Q000494:pharmacology*; D011963:Receptors, GABA-A / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D063065:Organophosphonates; D011437:Propylamines; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; C011649:3-aminopropylphosphonic acid; D001640:Bicuculline