Irregular activation of individual sweat glands in human sole observed by a videomicroscopy

Sweat secretion from individual sweat glands on the human sole was observed in four male subjects by using a videomicroscope and correlated with sudom otor neural activity recorded from the tibial nerve by means of microneurog raphy. Individual sweat glands could he distinguished as active, less activ e and inactive according to the incidence of sweat secretion during spontan eous sweating. The threshold amplitude of the sudomotor burst necessary for sweat secretion varied from gland to gland. The number of sweat secretion was significantly related to the threshold amplitude. Sweat glands often fa iled to produce sweat secretion even when a suprathreshold burst occurred: only 46.1 +/- 3.8% (mean +/- S.E.M.) of the suprathreshold bursts elicited sweat secretion. Failure of the sweat secretion tended to appear after seve ral bursts occurred consecutively with short intervals. In spite of the var iability in sweat gland activity. the number of sweat glands recruited was linearly related to the amplitude of the sudomotor burst (P < 0.001). Thus, although sweat secretion from each sweat gland depends primarily on the in tensity of sudomotor neural activity, the activity of each sweat gland may fluctuate temporally as the result of irregular activation of sudomotor fib ers and possibly some intrinsic factors of the gland. (C) 2001 Elsevier Sci ence B.V. All rights reserved.