Sweating in the intact horse and isolated perfused horse skin

1. In intact horses, heat-induced sweating occured initially as pulses, then as a continuous, synchronously fluctuating discharge. 2. I.V. adrenaline (Adr) induced sweating immediately; isoprenaline (Isop) elicited sweating after a delay; and phenylephrine (PhE) had no sudorific effect. 3. In isolated perfused skin, PhE induced an immediate small sweat discharge, Isop a slower sustained output and Adr a biphasic discharge. α- and β-adrenergic antagonists blocked the first and second phases, respectively, of Adr-induced sweating. 4. The observed sweating patterns are consistent with independent activation of α-adrenergic myoepithelium and β-adrenergic secretory cells in the sweat glands. 5. Microcirculatory changes apparently also influenced sweat discharge.