Seasonal variation in responsiveness of human eccrine sweat glands to phenylephrine.

The responses of eccrine sweat glands to intradermally injected phenylephrine were studied in six healthy male volunteers in two experiments carried out in February and June. Phenylephrine (10(-7)-10(-2) M, 50 microliters) had no consistent effect on sweat gland activity during February, but evoked dose-related increases in sweat gland activity during June. Responsiveness to phenylephrine could be antagonized by prazosin (10(-5) and 10(-4) M) added to the injection solution.