A comparison of effects measured with isotonic and isometric recording: I. concentration-effect curves for agonists

摘要

Concentration-effect curves were obtained with carbachol tested on isolated preparations of guinea-pig ileum taken from adjacent sites in the same animal, one recorded isotonically, the other isometrically: similar experiments were made with histamine as agonist and with carbachol on rat uterus(in oestrus). The position and steepness of the curves was expressed as the values of[EC_50]and the exponent, P: with carbachol or histamine on guinea-pig ileum the curves were significantly steeper with isotonic Recording(P < 0.02, sign test)and displaced towards lower concentrations(P < 0.05)but there were Significant correlations(P < 0.05)between values obtained with tissues from the same animal.