RESUMO
Muscle sympathetic nerve responses to sudden sensory stimuli have been elucidated in several studies on young healthy men, showing reproducible interindividual differences ranging from varying degrees of inhibition to no significant change, with very few subjects showing significant excitation. These individual response patterns have been shown to predict the neural response to mental stress, and coupled blood pressure responses. The aim of this study was to investigate whether pre-menopausal healthy women show similar neural and blood pressure responses. Muscle sympathetic nerve recordings from the peroneal nerve were performed in 34 healthy women (mean age 27±8 years) during sudden sensory stimuli (electrical stimuli to a finger) and 3 minutes of mental stress (forced arithmetics). After sensory stimuli 18 women showed varying degrees of inhibition of muscle sympathetic nerve activity (burst amplitude mean reduction 60%, range 34 to 100%). The remaining 16 showed no inhibition (mean 5%, range -31 to 28%; one subject exhibiting excitation). During 3 minutes of mental stress the normalized change in burst incidence for muscle sympathetic nerve activity correlated with the percentage change of muscle sympathetic nerve activity induced by the sensory stimulation protocol (r=0.64, p=0.0042). In contrast to men, the neural responses did not predict changes in blood pressure. Thus, pre-menopausal females show a similar range of individual differences in defence-related muscle sympathetic neural responses as men, but no associated differences in blood pressure responses. Whether these patterns are unchanged after menopause remains to be investigated.