Effects of the central administration of adrenomedullin 2/intermedin on the oxytocin-secreting neurons and sympathetic outflow in comparison with adrenomedullin in rats

Abstract

Adrenomedullin 2 (AM2)/intermedin belongs to the super family of AM and calcitonin gene-related peptide (CGRP). Centrally administered AM and AM2 activated hypothalamic oxytocin (OXT)-secreting neurons and increased plasma OXT level in rats. We examined the effects of centrally administered AM2 on neuroendocrine and autonomic nervous functions in comparison with those of AM in conscious rats. Plasma concentrations of OXT were significantly increased 10 and 30 min after central administration of AM and AM2. The effects of centrally administered AM2 were more potent stronger than those of AM. After pretreatmen of the CGRP receptor antagonist and AM receptor antagonist, the effects of centrally administered AM were completely inhibited on plasma OXT levels and on the c-fos gene expression in the supraoptic and paraventricular nuclei of the hypothalamus, whereas those of AM2 were incompletely inhibited. The mean arterial pressure (MAP) and heart rate were increased potently for an extended period after icv injection of AM and AM2 in urethane-anesthetized rats. The effects of AM2 were more potently stronger and long-lasting than those of AM on MAP. These data suggested that AM2 would have unknown receptor except CGRP and AM receptor in the central nervous system. [J Physiol Sci. 2007;57 Suppl:S173]