EFFECT OF HUMAN GALANIN ON THE RESPONSE OF CIRCULATING CATECHOLAMINESTO HYPOGLYCEMIA IN MAN

Human galanin (hGAL) is a neuropeptide with 30 amino acid residues tha t has been found in the peripheral and central nervous system, where i t often co-exists with catecholamines. In order to clarify the possibl e role of hGAL in the regulation of sympathoadrenomedullary function, the effect of a 60-min infusion of hGAL (80 pmol . kg(-1) . min(-1)) o n plasma epinephrine and norepinephrine responses to insulin-induced h ypoglycemia in nine healthy subjects was investigated. Human GAL admin istration significantly reduced both the release of basal norepinephri ne and the response to insulin-induced hypoglycemia, whereas it attenu ated the epinephrine response by 26%, with the hGAL-induced decrease i n epinephrine release failing to achieve statistical significance. Hum an GAL significantly increased the heart rate in resting conditions an d clearly exaggerated the heart rate response to insulin-induced hypog lycemia, whereas it had no effect on the blood pressure. We conclude t hat GAL receptor stimulation exerts an inhibitory effect on basal and insulin-induced hypoglycemia-stimulated release of norepinephrine. The se findings provide further evidence that GAL may modulate sympathetic nerve activity in man but that it does not play an important role in the regulation of adrenal medullary function.