Cardiovascular responses to morphiceptin in spontaneously hypertensive and normotensive rats.

In the urethane anesthetized spontaneously hypertensive rats (SHR) intraventricular injections of morphiceptin produced dose-related increase in heart rate and blood pressure. In contrary, intraventricular administration of morphiceptin in Wistar rats induced a fall in blood pressure and heart rate. Yohimbine antagonized pressor responses to morphiceptin in SHR. Naloxone counteracted both the stimulatory effects of morphiceptin in SHR as well as hypotensive responses in Wistar rats. Bilateral vagotomy blocked depressant action of morphiceptin in normotensive but failed to alter the pressor effects in SHR rats. After systemic injections of morphiceptin a fall in heart rate and blood pressure was obtained in both strains.