Gender differences in cutaneous vascular and autonomic nervous response to local cooling.

To investigate gender differences in cutaneous vascular reactivity to local cooling we performed cold exposure of one hand and measured laser Doppler (LD) flux on fingers ipsilaterally and contralaterally in a group of 10 healthy females and a group of 10 healthy males. The females were tested twice: in the early follicular and in the mid-luteal phase of the menstrual cycle. We related the characteristics of cutaneous vascular responses to indices of autonomic nervous system activity (heart rate, blood pressure, heart rate variability) at rest and during the cold challenge. In our experimental settings females exhibited greater cutaneous vascular response to local cooling at the ipsilateral site (LD flux decreased to 48.6 +/- 6.2 % of the resting value), as compared to males (LD flux decreased to 71.9 +/- 6.2 % of the resting value) as well as at the contralateral site (LD flux decreased to 68.2 +/- 6.1 % in females and to 85.6 +/- 3.8 % in males) (p < 0.05, Dunnett's test). The more pronounced cutaneous vascular response in females seems consistent with the finding of their lower sympathetic activity at rest as well as with their heart rate variability indices of greater sympathetic system reactivity to local cold exposure. Correspondingly, males showed a higher level of sympathetic nervous system activity at rest and a predominant reactivity of the parasympathetic system during local cooling at 15 degrees C. The females in our study, all of whom were premenopausal, exhibited intra-menstrual cycle variability only in cutaneous vascular response at the site of local cooling (LD flux decreased during the early follicular phase to 48.6 +/- 6.2 % and during the mid-luteal phase to 29.2 +/- 3.2 % of the resting value, p < 0.05, paired t-test), but not contralaterally. In addition, we found no intra-menstrual cycle differences in the indices of autonomic nervous system reactivity.