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The purpose of this study was to compare smokers and non-smokers' sudomotor and cutaneous vascular responses to whole-body passive heat stress. 9 regularly smoking (SMK; 29±9 y; 10±6 cigarettes/day) and 13 non-smoking (N-SMK; 27±8 y) males were passively heated until core temperature (TC) increased 1.5°C from baseline. Forearm local sweat rate via ventilated-capsule (LSR), sweat gland activation (SGA), sweat gland output (SGO), and cutaneous vasomotor activity via Laser Doppler flowmetry (CVC) were measured as mean body temperature increased (ΔTb) during passive heating using a water-perfused suit. Compared to N-SMK, SMK had a smaller ΔTb at the onset of sweating (0.52±0.19 versus 0.35±0.14°C, respectively; p=0.03) and cutaneous vasodilation (0.61±0.21 versus 0.31±0.12°C, respectively; p<0.01). Increases in LSR and CVC per °C ΔTb (i.e., sensitivity) were similar in N-SMK and SMK (LSR: 0.63±0.21 versus 0.60±0.40 versus Δmg/²/min/°C ΔTb, respectively, p=0.81; CVC: 82.5±46.2 versus 58.9±23.3 Δ%max/°C ΔTb, respectively; p=0.19). However, plateau in LSR during whole-body heating was higher in N-SMK versus SMK (1.00±0.13 versus 0.79±0.26 mg·cm²·min; p=0.03), which was likely a result of higher SGO (8.94±3.99 versus 5.94±3.49 μg·gland-1·min-1, respectively; p=0.08) and not number of SGA (104±7 versus 121±9 glands/cm², respectively; p=0.58). During whole-body passive heat stress, smokers had an earlier onset for forearm sweating and cutaneous vasodilation, but a lower local sweat rate that was likely due to lower sweat output per gland. These data provide insight to local (i.e. forearm) thermoregulatory responses of young smokers during uncompensatory whole-body passive heat stress. [ABSTRACT FROM AUTHOR]

Human and animal studies on sleep-disordered breathing and respiratory regulation show that the effects of sex hormones are heterogeneous. Because neonatal stress results in sex-specific disruption of the respiratory control in adult rats, we postulate that it might affect respiratory control modulation induced by ovarian steroids in female rats. The hypoxic ventilatory response (HVR) of adult female rats exposed to neonatal maternal separation (NMS) is 30% smaller than controls (24), but consequences of NMS on respiratory control in aging female rats are unknown. To address this issue, whole body plethysmography was used to evaluate the impact of NMS on the HVR (12% O2, 20 min) of middle-aged (MA; 57 wk old) female rats. Pups subjected to NMS were placed in an incubator 3 h/day for 10 consecutive days (P3 to P12). Controls were undisturbed. To determine whether the effects were related to sexual hormone decline or aging per se, experiments were repeated on bilaterally ovariectomized (OVX) young (12 wk old) adult female rats. OVX and MA both reduced the HVR significantly in control rats but had little effect on the HVR of NMS females. OVX (but not aging) reduced the anapyrexic response in both control and NMS animals. These results show that hormonal decline decreases the HVR of control animals, while leaving that of NMS female animals unaffected. This suggests that neonatal stress alters the interaction between sex hormone regulation and the development of body temperature, hormonal, and ventilatory responses to hypoxia. [ABSTRACT FROM AUTHOR]