Effect of propranolol on heart rate, blood pressure and plasma noradrenaline during coitus in the rabbit.

1. The effects of coitus on heart rate, blood pressure and plasma concentration of noradrenaline were studied in six male rabbits. 2. During coitus, heart rate rose from 228 +/- 6 to 324 +/- 8 beats/min (mean +/- SEM; n = 24). Mean blood pressure rose from 87 +/- 3 to 165 +/- 4 mmHg, and plasma concentration of noradrenaline from 2.07 +/- 0.21 to 5.02 +/- 0.26 nmol/l. The maximum heart rate did not occur until after the peak in blood pressure. 3. Propranolol had no effect on the power expended during coitus, but there was a dose dependent fall in the changes in heart rate, blood pressure and plasma concentration of noradrenaline.