Regional differences in human eccrine sweat secretion following thermal and non-thermal stimulation
In a previous communication (Taylor, 2000), we have shown, under open-loop conditions, that the skin has a generally uniform thermosensitivity. That is, with the exception of the face, sensory awareness and the feedback-effector relationship for sweating was surprisingly similar when body surfaces were presented with equivalent thermal stimuli (Cotter and Taylor, 2005). However, within the closed-loop state, there are many interactions between the cutaneous and central thermosensitive tissues. In fact, warm- and cold-sensitive hypothalamic neurons receive cutaneous, spinal and other central thermoafferent feedback, and these not only modify the firing rate of hypothalamic neurons, but also affect their sensitivity to core temperature changes. Thus, while open-loop experiments provide elemental detail pertaining to the characteristics of discretely-controlled thermoafferent signals, they do not necessarily inform us concerning the interaction of central and peripheral thermoafferents within closedloop systems, either during steady states or thermal transients. Therefore, the focus is this communication will be upon regional variations in human effector function during both endogenous and exogenous (passive) thermal loading, but with feedback loops closed (operating). The effector function of interest is eccrine sweat secretion, and we shall briefly overview this topic with respect to thermal and non-thermal stimulations prior to, and following thermal adaptation.