Adrenomedullin 2 microinjection into nucleus tractus solitarius elevates blood pressure and heart rate

Abstract

Adrenomedullin 2 (AM2)/Intermedin, as a novel member of calcitonin/calcitonin gene-peptide (CGRP) family, has been reported to play diverse physiological roles. The previous studies have showed that intravenously and intracerebroventricular (ICV) administrations of AM2 can produce strong influences on cardiovascular activities. To examine the physiological role of AM2 in the nucleus tractus solitarius (NTS) to regulate cardiovascular activities, we directly microinjected AM2 into the NTS. In 36 urethane-anesthetized male Wistar rats, AM2 (10 pmol, 20 pmol and 40 pmol/100 nl) was unilaterally microinjected into the NTS, where L-glu microinjection induced typical depressor and bradycardic responses, resulting in significant transient increases on mean arterial pressure (MAP) and heart rate (HR). Microinjection of vehicle (artificial cerebrospinal fluid, 100 nl) had no significant effects on MAP and HR. This study demonstrates that AM2 acting in NTS induces significant cardiovascular responses. In addition, to clarify further whether the actions of AM2 in NTS are related to the CRLR/RAMP receptor complexes, we are examining the expression of these receptors in NTS using real time PCR and immunohistochemistry analysis. [J Physiol Sci. 2008;58 Suppl:S153]