The role of alpha1- and alpha2-adrenoceptors in gender differences in cutaneous LD flux response to local cooling.

The present study was designed to assess the hypothesis that alpha2-adrenergic response plays a predominant role in sex differences in cutaneous microvascular response to cold. For this purpose, we studied the effect of the selective alpha1-antagonist prazosin (1 microl of 1.2 mM solution) and the alpha2-antagonist yohimbine (1 microl of 12 mM solution) microinjected into the skin area where the laser-Doppler (LD) flux response to local cooling was measured in healthy male and female subjects. Multiple regression analysis showed correlation between LD flux response at the site of local cooling (direct response) and gender (P = 0.039). The LD flux decrease was smaller in males. The application of the yohimbine significantly diminished the LD flux response at the site of local cooling in females but not in males (P < 0.05). In contrast, the injection of prazosin did not significantly affect the response. These findings strongly support the suggestion of a decisive role of alpha2-adrenoceptors in cold-induced gender difference at the level of cutaneous microvasculature at the site of local cooling. Multiple regression analysis of LD flux response to cold exposure at the site distant to cooling (indirect response) also confirmed correlation between LD flux response and gender (P = 0.022). The LD flux decrease was smaller in males. The alpha1-antagonist abolished the LD flux response to cold exposure (P = 0.000). These results corroborate the importance of alpha1-adrenoceptors in skin microcirculatory response to indirect local cooling mediated by the sympathetic vascular reflex.