Sweat gland function in isolated perfused skin.

1. A technique for perfusion of skin has been used to investigate a possible neurochemical basis for the different patterns of sweating in domestic animals. Evaporative water loss was measured from excised trunk skin, ears or tails perfused with a nutrient Krebs solution, to which drugs were added as required. Perfused skin was observed to sweat in response to administration of sudorific drugs, and some features of the patterns of sweating were similar to those which could be induced by heating or by drugs in conscious animals. 2. In sheep and goat skin, injections of adrenaline, and to a lesser extent of noradrenaline, elicited brief sweat discharges but these were not sustained when the drugs were infused during 10-20 min. Injections of isoprenaline, carbachol, 5-HT, bradykinin, oxytocin and histamine were all ineffective. 3. Injections of adrenaline into cattle skin evoked longer-lasting sweat discharges, and infusions of adrenaline elicited continuous discharges. Injections of noradrenaline and sometimes of bradykinin caused only brief sweat discharges; other drugs were ineffective. 4. In horse and donkey skin, injections or infusions of noradrenaline, oxytocin and bradykinin elicited brief discharges of sweat. Infusions of isoprenaline caused a continuous and profuse outflow of sweat. Infusions of adrenaline also caused a continuous discharge which was usually biphasic in its onset. Other drugs were ineffective. 5. Assuming that the brief sweat discharges are due to myoepithelial contractions and the continuous discharges to sustained increases in secretion, equine sweat glands seem to have a alpha-adrenergically controlled myoepithelium and a beta-adrenergically controlled secretory mechanism. Sheep and goats may have a similar alpha-adrenergic control of the sweat gland myoepithelium but only a feeble sweat secretory mechanism. In cattle, an alpha-adrenergic mechanism appears to control sweat secretion, but the control of the myoepithelium is uncertain.