Sweating and body temperatures following abrupt changes in environmental temperature

Human subjects were transferred between environments imposing different levels of heat stress. Analyses of measurements obtained after a reasonably steady state had been achieved in each of several environments revealed equally good correlation between a) sweat rate and ear temperature (tympanic membrane), and b) sweat rate and calculated deep skin temperature (hypothetical). The correlations are consistent with adjustment of sweating in response to either hypothalamic temperature or temperature of skin receptors or some combination of the two. However, during the first 20 min after transfer, changes in sweat rate and skin temperature occurred together and in the same direction, but were not accompanied by any consistent change in ear temperature. Thus, to the extent that ear temperature represents hypothalamic temperature, an hypothesis of control of sweating based on hypothalamic temperature alone is not tenable. Alternative physiological explanations are given for data developed elsewhere and used in support of an hypothesis of sweat control solely from the hypothalamus.

Submitted on August 14, 1961

Sweating responses in the horse

The sweat glands of the horse are very sensitive to L-adrenaline, 0·5 to 1·0 μ g/kg, i-v. being enough to cause general sweating. Given intradermally, the threshold dose is usually about 0·1 μ g; this causes local sweating, lasting for an hour or more, and spreading as a clear-cut track along superficial lymphatic vessels for long distances. This striking result has not previously been recognized. The action of adrenaline is not inhibited by any of seven adrenaline antagonists which were tried. No piloerection is caused within a few hours by adrenaline. L- nor -Adrenaline, by either route causes no sweating, or only a little locally an hour or two after i-d. injection; but tracks of hair erection identical with the adrenaline sweating tracks appear, and on i-v. injection in doses of 5 mg or over, general piloerection occurs. The piloerection is inhibited by dibenamine. Parasympathomimetic substances (acetylcholine, Carbachol) cause sweating when given in suitable doses, either i-d. or i-v.; their action is inhibited by atropine, and augmented by anticholinesterases. The sweating on i-v. injection is probably due to adrenaline release from the adrenals, that on i-d. injection to skin vaso-dilatation. Factors which increase the skin circulation favour, or cause, sweating, and vice versa. Hence sympathetic denervation leads to prolonged and profuse sweating, and subsequently to an increased tendency to sweat, lasting for more than 3 months. There is little evidence to favour the view that the sweat glands in the horse normally respond to, or are provided with the necessary innervation for, the action of nerves, sym­pathetic or otherwise, but strong evidence that they normally respond to an increase in the amount of adrenaline in the blood, or to increased blood supply. The latter is under nervous control. After i-d. injections of adrenaline the skin is anhidrotic for some days. This may throw light on the condition of tropical anhidrosis.