Effects of capsaicin application on the skin during resting exposure to temperate and warm conditions

Abstract

We investigated thermoregulatory and cardiovascular responses at rest in a temperate (20°C) and in a warm (30°C) environment (40% RH) without and with the application of capsaicin on the skin. We hypothesized that regardless of environmental temperature, capsaicin application would stimulate heat loss and concomitantly deactivate heat conservation mechanisms, thus resulting in rectal temperature (Tre) and mean blood pressure decline due to excitation of heat‐sensitive TRPV1. Ten male subjects were exposed, while seated, for 30 minutes to 20.8 ± 1.0°C or to 30.6 ± 1.1°C: without (NCA) and with (CA) application of capsaicin patches on the skin. Thermoregulatory (Tre, proximal‐distal skin temperature gradient) and cardiovascular variables (modelflow technique) as well as oxygen uptake were continuously measured. The area under the curve for Tre decline at 20°C was smaller in CA (−2.1 ± 1.3 a.u.) than in NCA (−0.6 ± 1.1 a.u., P < 0.01, r = 0.8). Likewise, at 30°C it was smaller in CA (−2.2 ± 2.1 a.u.) compared to NCA (−0.8 ± 2.0 a.u., P = 0.02, r = 0.7). Local vasomotor tone and oxygen uptake, were significantly lower by 36.7% ± 94.2% and 12.3% ± 12.3%, respectively, with capsaicin compared to NCA (P = 0.05 and P < 0.01, respectively). Additionally, in 30°C CA mean arterial pressure was lower by 10.7% ± 5.9%, 8.9% ± 5.9%, and 10.6% ± 7.0% compared to 30°C NCA, 20°C NCA, and 20°C CA, respectively (P < 0.01, P = 0.02, and P < 0.01, respectively, d = 1.4‐1.8). In conclusion, capsaicin application on the skin induced vasodilation and Tre decline. At 30°C CA, thermal responses were accompanied by arterial hypotension most likely due to the interactive effects of both stressors (warm environment and capsaicin) on cutaneous vascular regulation.

Thermoregulatory and cardiovasculareffects of capsaicin application on human skin during dynamic exercise to temperate and warm conditions

“…As a consequence, the cycling time needed for subjects' rectal temperature to reach 38.2°C was increased by 5 min approximately in capsaicin compared to the noncapsaicin condition. The present findings are in accordance with our previous work in resting humans (Botonis et al, 2019), indicating that capsaicin application on the skin (5% of the skin surface area) induces significant rectal temperature decline as a result of TRPV1 activation. Extending this knowledge, the present study showed that during cycling, the estimated vasoconstrictive tone was lower and the sweating rate was higher, with its initiation occurring at lower rectal temperature rise, after capsaicin application, thus resulting in a slower rectal temperature increase.…”

“…A recent study in humans (Botonis et al, 2019), confirming previous observations in animals (Donnerer & Lembeck, 1983;Jansco-Cabor, Szolcsanyi, & Jancso, 1970), demonstrated a significant rectal temperature decline during resting conditionas a result of capsaicin application on subjects' skin. Along these lines, studies conducted in vivo have shown that TRPV1 channels contribute to thermal hyperaemia (Wong & Fieger, 2010) accompanied by cutaneous active vasodilation (Wong & Fieger, 2012).…”

“…Unexpectedly to findings at rest (Botonis et al, 2019), heat production (oxygen uptake) was higher during exercise with than without capsaicin application. However, this finding is in accordance with experiments in resting rats (Hursel & Westerterp-Plantega, 2010), which have shown that capsaicin may increase heat production by enhancing catecholamine secretion from the adrenal medulla, mainly through activation of central nervous system.…”

“…It is well-documented that heat-sensitive and cold-sensitive temperature receptor potential (TRP) channels significantly contribute to mammals' temperature regulation (Caterina, 2007;Romanovsky et al, 2009). To date, a series of studies have proven that the application of chemical agonists of heat-sensitive TRP vanilloid 1 (TRPV1; e.g., capsaicin) or cold-sensitive TRP Melastatin8 (TRPM8) channels (e.g., menthol) on the skin can be used as a novel approach for investigating the integrative mechanisms affecting humans' temperature (Botonis, Geladas, Kounalakis, Cheouveim, & Koskolou, 2017;Botonis, Kounalakis, Cherouveim, Koskolou, & Geladas, 2018;Kounalakis, Botonis, Koskolou, & Geladas, 2010) and vascular regulation (Botonis, Miliotis, Koskolou, & Geladas, 2019;Ives et al, 2017).…”

“…Alongside its thermoregulatory properties, skin TRPV1 activation through capsaicin application may be promising for promoting blood pressure homeostasis (McCarty, DiNicolantonio, & O'Keefe, 2015). It was recently demonstrated that along with heat loss activation, capsaicin induces arterial hypotension in resting subjects exposed to 30°C (Botonis et al, 2019). Moreover, the hypotensive effect of capsaicin has been verified during static exercise protocols in animals (Ichiyama, Ragan, Bell, & Iwamoto, 2002) and humans (Dawson, Walser, Jafarzadeh, & Stebbins, 2004;Vianna, Fernandes, Barbosa, Teixerira, & Nobrega, 2018).…”