Opioid peptide modulation of circulatory response to hyperventilation in humans

After hyperventilation. systolic blood pressure (SBP) significantly decreas ed in 10 subjects (group 1), did not change in eight (group 2) and increase d in 15 (group 3). Diastolic blood pressure and heart rate increased in all groups. The decrease in SEP was associated with a decrease in plasma catec holamines and increase in beta -endorphin, whereas the increase in SEP was accompanied by an increase in catecholamine and Met-enkephalin levels. Nalo xone abolished the hyperventilation-induced SEP and catecholamine decrease only in group 1. These findings show an activation of the endogenous opioid system after hyperventilation and the role of beta -endorphin in reducing SEP in response to the test. (C) 2000 Elsevier Science Inc. All rights rese rved.