Temperature dependency of P2 receptor-mediated responses.

The P2 receptor-mediated responses of isolated guinea pig urinary bladder and vas deferens (P2X receptors) and taenia caeci (P2Y receptors) were registered at the three temperature conditions of 30, 37 and 42 degrees C. The contractile responses of both urinary bladder and vas deferens to a P2X receptor agonist alpha,beta-methylene ATP (alpha,beta-meATP; 0.01-30 microM) and to electrical field stimulation (1-64 Hz, 0.1 ms, supramaximal voltage) in the presence of atropine (0.1 microM) and phentolamine (1 microM) were markedly more prominent at a temperature of 30 degrees C than at 37 or 42 degrees C. Similarly, relaxation of carbachol-precontracted taenia caeci caused by electrical field stimulation (0.5-8 Hz, 0.1 ms, supramaximal voltage) temperature-dependently increased with decrease of temperature, while relaxation of this tissue by exogenous ATP (1-100 microM) was not affected by the temperature. A P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 1-30 microM) at all three temperature conditions concentration-dependently antagonised contractile responses to alpha,beta-methylene ATP and electrical field stimulation in both urinary bladder and vas deferens. PPADS, even at the highest concentration tested (30 microM), had no effect on the relaxant responses of the taenia caeci either to electrical field stimulation or ATP and its action was not affected by the change of temperature. It is concluded from this study that the effectiveness of P2 receptor-mediated responses in guinea pig urinary bladder, vas deferens and taenia caeci increases by decrease of temperature.