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CARDIOVASCULAR EFFECTS OF CENTRAL ADMINISTRATION OF β‐ENDORPHIN IN RATS RECEIVING NEONATAL INJECTION OF MONOSODIUM GLUTAMATE
Author(s) -
Wong T. M.,
Lee A. Y. S.,
Chan R. K. W.
Publication year - 1989
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1989.tb01904.x
Subject(s) - monosodium glutamate , medicine , endocrinology , (+) naloxone , beta endorphin , glutamate receptor , ventricle , endorphins , third ventricle , receptor , cerebral ventricle , blood pressure , lateral ventricles , opioid , anatomy
SUMMARY 1. The effects of intracerebroventricular (i.c.v.) and intracisternal (i.e.) injection of β‐endorphin on arterial blood pressure (BP) in rats that received five intraperitoneal injections of monosodium glutamate (MSG) on alternate days in the first 10 days of life were studied. 2. β‐endorphin administered into the lateral ventricles caused a prolonged elevation in BP, whereas i.c. injection of the peptide resulted in an even longer lasting reduction in BP. In the MSG‐treated rat, the prolonged hypertensive effect of i.c.v. injection of β‐endorphin was completely abolished, but the effect of i.c. injection of the peptide was the same as that in the control. Since MSG treatment destroyed selectively the structures around the third ventricle, it is suggested that these structures, including the arcuate nucleus, may be responsible for mediating the cardiovascular effects of β‐endorphin. 3. The effects of central administration of β‐endorphin were completely blocked by naloxone, which mainly antagonizes the actions of μ‐receptor agonists and has no cardiovascular effects itself. The results suggest that μ‐receptors may be involved in mediation of the effects of β‐endorphin on the cardiovascular system and that β‐endorphin in the brain may not exert a tonic influence on the cardiovascular functions.