title: Relaxation of guinea-pig fundic strip by adenosine, adenosine triphosphate and electrical stimulation: lack of antagonism by theophylline or ATP treatment.
abstract: 1 Theophylline relaxed isolated strips of guinea-pig stomach fundus in a dose-dependent manner; above 50 to 100 microM responses showed no fade for up to 90 min. 2 Relaxant responses to adenosine, adenosine triphosphate (ATP), noradrenaline, and to electric field stimulation of non-adrenergic inhibitory nerves were not affected in a significant manner in the presence of 50 microM theophylline. 3 In tissues which showed complete fade of initial responses in the continued presence of 50 microM ATP, the effects of stimulation of non-adrenergic inhibitory nerves remained unaltered, suggesting that the ATP receptor has no function in non-adrenergic inhibitory transmission in this tissue. 4 These findings are opposite to those of Okwuasaba, Hamilton & Cook (1977), who claimed that 50 microM theophylline almost fully inhibited relaxation induced by adenosine ATP and nerve stimulation and that ATP-induced fade also abolished sensitivity to inhibitory nerve stimulation.
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D013270:Stomach / Q000187:drug effects; D013806:Theophylline / Q000494:pharmacology*
chemical_list: D000255:Adenosine Triphosphate; D013806:Theophylline; D000241:Adenosine