Estimation of regional cutaneous cold sensitivity by analysis of the gasping response

Abstract

Regional cutaneous sensitivity to cooling was assessed in males by separately immersing four discrete skin regions in cold water (15 degrees C) during head-out immersion. The response measured was gasping at the onset of immersion; the gasping response appears to be the result of a nonthermoregulatory neurogenic drive from cutaneous cold receptors. Subjects of similar body proportions wore a neoprene "dry" suit modified to allow exposure to the water of either the arms, upper torso, lower torso, or legs, while keeping the unexposed skin regions thermoneutral. Each subject was immersed to the sternal notch in all four conditions of partial exposure plus one condition of whole body exposure. The five cold water conditions were matched by control immersions in lukewarm (34 degrees C) water, and trials were randomized. The magnitude of the gasping response was determined by mouth occlusion pressure (P0.1). For each subject, P0.1 values for the 1st min of immersion were integrated, and control trial values, although minimal, were subtracted from their cold water counterpart to account for any gasping due to the experimental design. Results were averaged and showed that the highest P0.1 values were elicited from whole body exposure, followed in descending order by exposures of the upper torso, legs, lower torso, and arms. Correction of the P0.1 response for differences in exposed surface area (A) and cooling stimulus (delta T) between regions gave a cold sensitivity index [CSI, P0.1/(A.delta T)] for each region and showed that the index for the upper torso was significantly higher than that for the arms or legs; no significant difference was observed between the indexes for the upper and lower torso.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurophysiology of Skin Thermal Sensations

“…The fact that local cooling of the abdomen has been shown to induce vasoconstriction of the corresponding underlying gastrointestinal tract, with a potentially significant impact on this organ's function (185), supports the hypothesis for which the higher cold sensitivity of the abdomen might represent a form of evolutionary-acquired thermosensory adaptation aimed at optimizing thermal homeostasis (226). Further evidence in support of the physiological significance of the higher cold sensitivity of the torso (than of the limbs) is provided by the observation that the gasping response to sudden skin cooling, resulting from cold water immersion, is significantly greater when the torso is the region exposed to the immersion (30). As the gasping response (i.e.…”

“…Along with these fundamental parameters, the location of the thermal stimulation on the body can also influence subjective thermal sensations (30). Indeed, regional differences in thermal sensitivity across the human body have long been observed (137).…”

“…This, despite the fact that the application of the same cold stimulus resulted in a smaller decrease in skin temperature of the lower back than of the lateral chest. This observation led to the conclusion that that regional differences in sensitivity to cold could therefore be determined by an heterogeneous integration of thermo-afferent information, which appears to be independent of regional changes in skin temperature (8,30,226).…”

“…As the gasping response (i.e. hyper-ventilatory response occurring at the onset of head-out cold-water immersion) is by definition a non-thermoregulatory response driven by neurogenic drive from cold thermoreceptors (30), the fact that the magnitude of this physiological response is influenced by the skin region exposed to cooling (e.g. greater for the torso than the limbs) indicates that, whether due to a higher density of cold thermoreceptors, or to a greater central influence on thermal sensation, different skin regions present distinctively different thermal sensitivities to cold.…”

Sex-biased maternal effects reduce ectoparasite-induced mortality in a passerine bird

“…Although ectoparasite exposure of breeding females can induce greater egg allocation of maternal steroids that facilitate nestling growth or begging, such allocation can have detrimental effects on growth of the sexes if male and female offspring differ in growth requirements (39)(40)(41). Differential production of male and female eggs in relation to laying sequence, as observed in this study, not only enables mothers to allocate hormones differentially to each sex, but may also provide the mechanism by which hormone fluctuations in maternal plasma because of ectoparasite exposure produce sex-biased laying order.…”