Analgesia and anaesthesia produced by fentanyl, urethane and ether, but not pentobarbital, occured concomitantly with an increase in the concentration of plasma beta-endorphin like immunoreactivity (BEIR), probably of pituitary origin. This increase was not associated with significant changes in pituitary or brainstem beta-endorphin content. Pretreatment with naloxone caused a reduction in plasma BEIR increase following HypnormR, ether and urethane; and in the analgesia following HypnormR and urethane. Pentobarbital, alone or in combination with naloxone, did not increase the concentration of plasma beta-endorphin. These results may indicate participation of endogenous opioids in the mechanism of action of urethane.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)