Role of Opioid Peptides in Brain Mechanisms Regulating Blood Pressure

¹ Rudolf Magnus Institute for Pharmacology, Medical Faculty, University of Utrecht, Utrecht, The Netherlands

Beta-endorphin and related opioid peptides are neuropeptides which appear to play a role in cardiovascular regulation which is supported by altered nociceptive responsiveness in hypertensive animals. In spontaneously hypertensive rats the pain threshold for electric stimulation is elevated; these rats show increased response latency time in a hot plate test. The opiate antagonist naloxone reverses these values to that of the normotensive controls. In other forms of experimental hypertension, eg, renal hypertension (one-clip, two-kidney model), no change in pain sensitivity is apparent. Sinoaortic baroreceptor denervation causes a labile hypertension without changes in hot plate response. Administration of β-endorphin into the nucleus of the solitary tract (NTS) gradually decreases blood pressure and heart rate without affecting respiratory frequency. These cardiovascular effects are blocked by naloxone as well as by an antibody to β-endorphin. In contrast to the effects of β-endorphin, microinjection of enkephalins into the NTS increases blood pressure and heart rate. The data suggest the existence of two separate endorphin systems at the level of the NTS, one a depressor and another a pressor system. The depressor influence of β-endorphin may play a role in the mechanism of action of antihypertensive agents such as methyldopa and clonidine. Our data support a role of endorphins as neuropeptides involved in cardiovascular regulation, exerting a dual influence at the level of the NTS.

This article has been cited by other articles:

				S. E. Sheifer, T. A. Manolio, and B. J. Gersh Unrecognized Myocardial Infarction Ann Intern Med, November 6, 2001; 135(9): 801 - 811. [Abstract] [Full Text] [PDF]