Temperature coefficients of affinity constants for the binding of antagonists to muscarinic receptors in the rat cerebral cortex.

1 The temperature coefficients of binding of a series of muscarinic antagonists to their receptors in membrane preparations from the rat cerebral cortex has been examined. 2 At 37 degrees C the affinity constants agree with those determined by antagonism of acetylcholine-induced contractions of the guinea-pig ileum. 3 The temperature-dependence of the affinity constants is low; for the antagonists examined, the affinity constants at 0 degrees C differ by less than a factor of 3 from those measured at 37 degrees C. 4 There are qualitative similarities between the estimates of the temperature coefficient of binding of the antagonists to receptors in ileum strips and in the cerebral cortex.