Abnormal sympathetic neural recruitment patterns and hemodynamic responses to cold pressor test in women with posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is more prevalent in women and associated with greater risk of major forms of cardiovascular disease, but physiological mechanisms underlying this association remain unknown. We hypothesized that abnormal sympathetic responses to sympathoexcitatory stimuli might predispose PTSD patients to a greater risk of cardiovascular disease. We examined changes in integrated muscle sympathetic nerve activity (MSNA) burst and multiunit action potential (AP) recruitment patterns as well as hemodynamic responses during cold pressor test (CPT) in 14 women with PTSD and 14 healthy control subjects. Data were collected during 1-min baseline, 2-min CPT, and 3-min recovery. At baseline, blood pressure (BP) was not different between groups; however, heart rate and sympathetic neural activity were greater in women with PTSD [MSNA burst frequency (BF): 27 ± 13 vs. 18 ± 14 bursts/min (P = 0.04); AP frequency: 272 ± 152 vs. 174 ± 146 spikes/min (P = 0.03)]. In response to CPT, BP responses exhibited a significant group × time interaction (P = 0.01) highlighted by a significant diastolic BP main group effect (P = 0.048) despite the finding that increases in integrated MSNA burst responses were not different between groups (P > 0.05). However, compared with control subjects, AP firing frequency (group > time interaction P = 0.0001, group P = 0.02) and AP per burst (group × time interaction P = 0.03, group P = 0.03) were augmented in women with PTSD. Collectively, women with PTSD exhibited a greater pressor response and an exaggerated sympathetic neural recruitment pattern during sympathoexcitatory stimuli that may, in part, explain the propensity toward developing hypertension and cardiovascular disease later in life. NEW & NOTEWORTHY The novel findings of the present study are that women with posttraumatic stress disorder (PTSD) have an augmented pressor response to the sympathoexcitatory stimulus of a cold pressor test (CPT) compared with healthy control subjects. Although integrated muscle sympathetic nerve activity burst responses were not significantly different between groups, total sympathetic action potential discharge in response to the CPT was markedly elevated in women with PTSD exhibiting increased firing of lowthreshold axons as well as the recruitment of latent subpopulations of larger-sized axons that are otherwise silent at baseline. Aberrant autonomic circulatory control in response to sympathoexcitatory stimulus may in part explain the propensity toward developing hypertension and cardiovascular disease in this population.