Effect of cerebellar adrenomedullin during acute stress

Adrenomedullin (AM) is a peptide involved in cardiovascular regulation. In the cerebellum, the density of AM receptors is altered during hypertension, suggesting a possible role of cerebellar adrenomedulinergic system in the regulation of blood pressure (BP). The aim of this study was to evaluate the functional role of AM during acute stress, by in situ administration of AM into the cerebellar vermis in rats. Adult normotensive Wistar Kyoto (WKY) and Sprague Dawley (SD) rats and spontaneously hypertensive rats (SHR), were anesthetized and later, their cerebellar vermis cannulated. Footshock was used as stressor. Animals were divided into groups that received either AM (0.2 and 200 pmol/5μL) or vehicle (physiological saline, 5μL). The BP was determined, using noninvasive digital plethysmography, before and after treatment, followed by the application of footshock (100V, 5 Hz, 10 msec, for 4 minutes). The results show that microinjection of AM (0.2 and 200 pmol) in situ into the cerebellar vermis in SD, WKY and SHR rats, significantly decreased the pressor response induced by footshock stress, suggesting that the hypotensive action is mediated through regulation of sympathetic outflow. Taken together, our results demonstrate a role of cerebellar AM in the regulation of cardiovascular response to stress.