During a class experiment conducted by one of the authors in England in 1949

Transcription

1 59 J Physiol. (I953) I22, ACTIVITY OF HUMAN SWEAT GLANDS DURING EXPOSURE TO COLD BY E. M. GLASER AND T. S. LEE From the Department of Physiology, University of Malaya, Singapore (Received 9 February 1953) During a class experiment conducted by one of the authors in England in 1949 it was necessary to make a human subject shiver in a cold room at 0 C. In order to achieve quick cooling the subject stripped to the waist, and when he began to shiver, sweat was seen to trickle from his axillae. The literature contains no record of such a phenomenon (although List & Peet, 1938, have mentioned that nervous persons may have moist hands and feet in winter), and the students were encouraged to follow up this di.scovery. They confirmed that sweating could take place during exposure to cold, but a systematic study of the problem was impossible at that time. An investigation has now been carried out: (1) to show whether sweating in a cold environment was a reproducible response or a freak observation, (2) to establish what regions were affected by such sweating, (3) to study the nervous mechanisms involved. METHODS Subject8 and procedure. Twenty separate experiments were performed on fourteen healthy men aged years, none of whom was apprehensive about the experiments. With the exception of one test, the subjects did not know the purpose of this investigation, and no comments were made in their presence. The subjects' axillae had been previously shaved and their arms were supported so that the hands and axillae were exposed. In sixteen experiments the initial measurements and such procedures as iontophoresis were carried out in a laboratory, and the subjects then moved into a constant temperature room which was either 3 or 8 yards away. In four experiments the subjects remained in a constant environment all the time: in three of these the subjects' lower limbs were immersed in water at C and slowly exercised, which causes a high venous return of cooled blood but little cooling of the body (Glaser & Jones, 1951), and in one experiment intravenous saline and adrenaline infusions were given to a recumbent subject. In order to accustom the subjects to the initial environment and posture 1 hr was always allowed to elapse before any procedures were begun. At the end of this period a check was made with starch and iodine (see below) to show whether there was any thermal or 'emotional' sweating. If such sweating was present, the preliminary period was extended. Technique&. The presence of sweat was demonstrated by Minor's method in which the skin is painted with a solution of 2% iodine and dusted with dry starch (Kuno, 1934, p. 30; List & Peet,

2 60 E. M. GLASER AND T. S. LEE 1938). This method is very sensitive, but in some experiments an iodine and starch-paper method was used (Randall, 1946) which allowed counting of active sweat glands. In a few experiments the presence of sweat was also demonstrated by direct measurement of the skin resistance, using ballpoint electrodes 1 cm apart. This method was comparatively insensitive (see below), but it was a useful check on the other methods. The skin temperature was measured with bare thermocouple wires closely adhering to the skin (Glaser, 1949) and the rectal temperature with a thermocouple mounted in a glass and rubber tube inserted to 10 cm from the sphincter (Glaser & Jones, 1951). Iontophoresis was carried out with a d.c. current of 3 ma and an anode area of 3 cm2. The cathode was moistened with physiological saline and had an area of about 100 cm2. Environmental condition8. The laboratory temperature varied from 27 to 300 C with an air humidity of %, but variations durin,g any one test were insignificant. The air movement was 40 m/min, but in a few instances, when sweat was present after the preliminary period of 1 hr, the air movement was raised to 200 m/min until sweating disappeared. The constant temperature room was well insulated and thermostatically controlled at levels ranging from 15 to 230 C, with an air humidity of 60% and an air movement of about 10 mimin. In two experiments, however, when the effects of cool air blasts were studied, the air movement was raised to 200 m/min. RESULTS Characteristics of sweating in a cold environment In eight experiments the subjects were in a cool environment for periods of 20 min to 1 hr at varying temperatures, preceded by an initial period at laboratory temperature, as described above. In one experiment the constant temperature room was at 22.5 C and neither shivering nor sweating was seen, although there was a slight fall of the rectal and skin temperature. In another the constant temperature room was at C and there was slight shivering but no sweating. In the remaining six experiments the temperatures were between 15 and 18 C, and both shivering and sweating were invariably seen. The presence of sweating could be demonstrated both with starch and iodine and by a decrease of the skin resistance, but starch and iodine showed up a few active glands as soon as sweating began, while changes of the skin resistance were not evident in corresponding points on the other side of the body until sweating was more diffuse. At temperatures of 180 C or less there was no correlation between the environmental temperature and the time of onset or the intensity of sweating. It was impossible, also, to correlate the skin or rectal temperature with sweating, for the latter set in at rectal temperatures between 37 and C, and sweating was observed in areas of skin which had been at temperatures between 20 and 340 C before sweating had begun and which remained at such temperatures while sweating was moderate. If the environmental temperature was 180 C or less, sweating invariably began within 5 min and frequently within 1 min of the onset of shivering, but there were two subjects in whom sweating also preceded visible shivering by 20 min. In both these, a single small outburst of sweating was noted during the initial steep fall of the skin temperature immediately after entering the constant temperature room, and in both experiments shivering was later accompanied by renewed sweating. The

3 SWEATING DURING COOLING 61 impression was gained that sweating was generally more marked when shivering was intense, but there were considerable individual variations in the intensity of both shivering and sweating. Regions affected. Although every region of the body surface was tested with starch and iodine and by measurements of the skin resistance (with the only exception of the immediate vicinity of the genitals and anus), sweating was always confined to the axillae, the hands and the feet (Figs. 1-3). There was invariably more sweat on the palms and soles than on the backs of the hands and feet, but some subjects sweated more in the axillae, others sweated more in the extremities. The control of sweating in a cold environment The nature of the secretory fibres. In six further experiments the constant temperature room was always at 150 C and, in addition to the previous procedure, substances were introduced into small skin areas of the hands and axillae. P1. 1 shows the axilla of one subject. Dihydroergotamine 1: 1000 had been introduced into the upper half of the axilla by iontophoresis, and atropine sulphate 1: 1000 had been similarly introduced into the lower half; the colour reaction between starch and iodine shows the presence of sweating in the upper area but not in the lower circular atropinized region of the axilla. The presence of 'gooseflesh' can also be noted on the skin. The inhibition of sweating by atropine but not by dihydroergotamine was similarly demonstrated both in the palm and the axilla in five other experiments. In three of these isotonic saline or water was introduced by iontophoresis as an additional control measure and this had no effects, but the introduction of atropine with a very fine needle into the skin of the palm and axilla was followed by an inhibition of sweating in a small area around the needle prick, while a similar injection of dihydroergotamine had no effect. Central nervous mechanisms. Two subjects were made to shiver (after the usual preliminary period at room temperature), in a sudden blast of cold air at 15 C, and one sweated within 30 sec while the other sweated within 3 mi of the onset of shivering. Sweating was again confined to the axillae, feet and hands. In two other experiments shivering was produced at 230 C by increasing the venous return from cooled lower limbs without cooling the whole body (see above), and in both these sweating of the palms and axillae was noted within 1 min of the onset of shivering. A further subject was similarly tested, but he neither shivered nor sweated. The action of adrenaline. In one experiment a subject weighing 61 kg lay on a couch at 230 C. After an initial period of 1 hr he was given an intravenous saline infusion at a rate of 40 drops/min. After another 15 min the infusion was transferred without the subject's knowledge (though not without his previous consent), to a constant delivery apparatus, and noradrenaline-free adrenaline

4 62 E. M. GLASER AND T. S. LEE.... Fig. 1. Fig. 2. Fig. 1. Sweating of the palm of the hand in a shivering person. (Dark spots indicate the colour reaction between starch and iodine.) Fig. 2. Sweating of the sole of the foot in a shivering person. Fig. 3. Sweating of the axilla in a shivering person.

5 THE JOURNAL OF PHYSIOLOGY, VOL. 122, No. 1 PLATE 1 Inhibition of sweating in a shivering person by introduction of atropine into the skin. Dihydroergotamine was introduced by iontophoresis into the upper portion of the axilla and atropine into the lower portion. Note complete absence of sweating in lower portion of axilla. 'Gooseflesh' can also be seen on the skin. To face p. 62

6 SWEATING DURING COOLING 63 was injected for 3 min at a rate of 25 p,g/min. This was accompanied by an increase of the pulse rate but no sweating. After an interval, during which the saline infusion was continued and during which the subject's pulse rate returned to its initial level, the infusion was again transferred to the constant delivery apparatus and adrenaline was injected for 5 min at a rate of 50,ug/min. This was immediately followed by sweating in the hands, feet and axillae (but not in other parts of the body surface), and it was accompanied by nausea, vomiting and headache. Owing to the need to give large doses of adrenaline this experiment was not repeated. Responses at the end of cooling In all tests in which the subjects had been sweating in the course of cooling there was a renewed outburst of sweating within 5 min of the end of cooling. The distribution of this sweating was the same as that observed in the cold room, but the forehead was sometimes involved. In these experiments sweating was absent in most of the body, and it is unlikely that its presence in some places should have been a result of condensation of moisture from warm room air on cool surfaces of the body. DISCUSSION It may be concluded that sweating of the hands, feet and axillae takes place in the course of cooling, at any rate in young men, and there is no reason to believe that such a phenomenon is confined to the Tropics, since the original observations were made in England. The present findings, however, justify no quantitative correlations, and the fact that all subjects shivered visibly at room temperatures below C does not imply that C is always a critical level. Sweat glands are known to be supplied by cholinergic fibres from the sympathetic nervous system (Dale & Feldberg, 1934; Chalmers & Keele, 1951), and it may be concluded that the sweat glands responsible for the above observations had a cholinergic innervation, since atropine always inhibited sweating in the cold while dihydroergotamine did not. Peculiarities of the local nerve supply, therefore, are not a likely cause of the phenomena observed. It seems improbable also that there should be a specific reflex mechanism for sweating in the cold, because sweating was present when shivering was elicited: (1) by cooling of the whole body; (2) by a nervous reflex from the skin (Jung, Doupe & Carmichael, 1937); (3) by an increased venous return of cooled blood from the lower limbs (Glaser & Jones, 1951); and also when there was no shivering at all. The present findings were not due to emotion, because some of the subjects were familiar with the procedures and environment and none showed signs of

7 64 E. M. GLASER AND T. S. LEE emotion, but sweating of the hands, feet and axillae invariably coincided with considerable central nervous activity, especially of the sympathetic centres. Thus, apart from the fact that sweating was always present when shivering was marked, it was also invariably present during the considerable vasomotor activity which took place when cooling ceased. Moreover, in two subjects there was some sweating when cooling began, and one subject sweated after a large dose of adrenaline. All these findings suggest that the neurones controlling the sweat glands of the hands, feet and axillae respond easily to various kinds of central nervous stimuli, and this is further borne out by the fact that mental effort (Kuno, 1934, pp ; Darrow, 1937) and emotion (List & Peet, 1938) also cause sweating in those parts. Sweating in the cold thus does not appear to be a freak effect but one of several types of sweating resulting from central nervous excitation, and it seems possible to conclude that the regions concerned with grasping of objects or with the production of body scent can sweat in response to almost any extensive central nervous activity. Such sweating is distinct from thermal sweating over the rest of the body (Kuno, 1934, pp ; List & Peet, 1938), but the difference may be mainly one of excitatory thresholds. Since areas concerned with 'emotional' sweating also sweat slightly during extreme heating (Kuno, 1934, pp ), while regions normally concerned with thermal sweating respond to strong emotional stimuli (McGregor, 1952), it seems probable that all parts of the body surface can sweat both in response to heating and to non-specific central nervous excitation, but that the pathways to the hands, feet and axillae have a low threshold for stimuli of non-specific origin. SUMMARY 1. Sweating of the hands, feet (especially of the palms and soles), and of the axillae usually takes place when people are shivering. It sometimes also takes place in a cool environment before shivering has begun. 2. There is no correlation between the degree of cooling and the onset of sweating. 3. The secretory nerve fibres involved are cholinergic. There is no evidence of any specific reflex mechanism responsible for sweating in a cold environment. 4. It is suggested that sweating in a cold environment and sweating from 'emotional' or 'mental' causes are all a result of non-specific central nervous excitation. The experiments mentioned in the introduction were carried out at the Department of Experimental Medicine, Cambridge, in by Mr Trevor Shaw and others.

8 SWEATING DURING COOLING 65 REFERENCES CHALMERS, T. M. & KEELE, C. A. (1951). Physiological significance of the sweat response to adrenaline in man. J. Phy8iol. 114, DALE, H. H. & FELDBERG, W. (1934). The chemical transmission of secretory impulses to the sweat glands of the cat. J. Physiol. 82, DARROW, C. W. (1937). Neural mechanisms controlling the palmar galvanic skin reflex and palmar sweating. A consideration of available literature. Arch. Neurol. Psychiat., Chicago, 37, GLAsim, E. M. (1949). The effects of cooling and of various means of warming on the skin and body temperature of men. J. Physiol 109, GLASER, E. M. & JONES, R. V. H. (1951). Initiation of shivering by cooled blood returning from the lower limbs. J. Physiol. 114, JUNG, R., DOUPE, J. & CARmcHAEL, E. A. (1937). Shivering: A clinical study of the influence of sensation. Brain, 60, KUNO, Y. (1934). The Phy8iology of Human Perspiration. London: Churchill. LIST, C. F. & PEET, M. M. (1938). Sweat secretion in man. 1. Sweating responses in normal persons. Arch. Neurol. Psychiat., Chicago, 39, MCGREGOR, I. A. (1952). The sweating reactions of the forehead. J. Physiol. 116, RANDALL, W. C. (1946). Quantitation and regional distribution of sweat glands in man. J. clin. Invest. 25, PH. CXXII. 5