The denervated cremaster muscle of the guinea-pig as a pharmacological preparation.

The pharmacological responses of both denervated and innervated cremaster muscle preparations from the guinea-pig have been investigated and compared. Acetylcholine (ACh) dose-response curves were obtained in both preparations. The affinity constants for (+)-tubocurarine and for atropine were calculated and indicated that the ACh receptors in both preparations were nicotinic. Histamine dose-response curves could be obtained only in the denervated preparation. The response was unaltered by metiamide, and the affinity constant for mepyramine fitted in with those previously obtained by others on ileum and trachea, indicating that the histamine receptors are H1 in type. Sustained contractions were obtained to adrenaline and noradrenaline but not isoprenaline, with the denervated preparations. Schultz-Dale responses were obtained with denervated muscle in sensitized guinea-pigs. This preparation did not respond to 5-hydroxytryptamine, bradykinin, or the slow-reacting substance of anaphylaxis.