HUMAN GALANIN REDUCES PLASMA NOREPINEPHRINE LEVELS IN MAN

The neuropeptide galanin (GAL) is widely distributed in the peripheral and central nervous systems, where it often coexists with catecholami nes. To gain insight into the action of human GAL on sympathetic nervo us system activity in man, we investigated the effects of a 60-min inf usion of human (h) GAL (80 pmol/kg . min) or saline on peripheral nore pinephrine (NE) and epinephrine concentrations, heart rate (HR), and s ystolic and diastolic blood pressure (BP) in the supine position as we ll as after assumption of the upright posture (UP) in eight healthy ma le volunteers. hGAL depressed supine plasma NE (0.84 +/- 0.06 vs. 0.33 +/- 0.02 nmol/L) and blunted the NE response to assumption of the UP (1.68 +/- 0.03 vs. 0.44 +/- 0.03 nmol/L), but-caused a significant enh ancement of the epinephrine response to assumption of the UP (0.22 +/- 0.02 vs. 0.65 +/- 0.06 nmol/L). hGAL significantly increased supine H R (70 +/- 2 vs. 99 +/- 4 beats/min) and potentiated the HR response to assumption of the UP (82 +/- 3 vs. 107 +/- 4 beats/min), hGAL did not alter supine systolic and diastolic BP, but caused a significant decr ease in the systolic (121 +/- 3 vs. 98 +/- 2 mm Hg) and diastolic (74 +/- 2 vs. 62 +/- 2 mm Hg) BP responses to assumption of the UP. Our da ta show that hGAL decreases supine position- and UP-stimulated release of NE, suggesting an inhibitory modulation of hGAL on sympathetic out flow in man. The finding that hGAL induces an increase in HR, both in the supine position and after UP, and an inhibition of the systolic an d diastolic BP response to UP provides further support for an involvem ent of hGAL in regulation of the cardiovascular and autonomic nervous systems in man.