PRESSOR EFFECT OF NALOXONE IN ACUTE EXPERI-MENTAL RABBITS / 中国药理学通报

ABSTRACT

Experiments were carried out on the anesthetized, operated and paralyzed rabbits to study if endogenous opioids are involved in the cardiovascular activity in the acute experimental conditions under which many experiments of pharmacology & physiology were performed. In 6 rabbits, low dose naloxone (0.4 mg/kg, i.v. ) caused sevral temporary pressor waves in 2.9?1.1 min after the injection & apperance of the arrhythmias in 2 animals. In other 9 rabbits, high dose naloxone ( 5 mg/kg, i.v.) raised basal blood pressure in 13.9?7.4 min after the injection, and caused arrhythmias in 5 animals. When the pressor effect was the highest, monoamine metabolites did not change significantly in CSF sampled from the terminal of midbrain aquaduct. Our other experiment has showed that NA & MHPG of the CSF increased during the central stimulation-induced pressor effect. Thus, it is supposed that endogenous opioids play an inhibitory effect on the cardiovascular system in the conditions like present experiment, and the peripheral opioid receptors which are poorly sensitive to naloxone may be involved in the effect.