Increased brain norepinephrine metabolism correlated with analgesia produced by the periaqueductal gray injection of opiates.
Dose-dependent increases in 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MOPEG-SO4), a major metabolite of norepinephrine, were produced in the limbic forebrain and cerebral cortex 30 min after the bilateral injection of morphine into the periaqueductal gray (PAG). These effects were also elicited by similar injections of levorphanol. Highly significant correlations were obtained between the concentrations of MOPEG-SO4 and the analgesic effect of the opiates and opiate actions were antagonized by systemic naloxone. These results indicate that activation of opiate receptors in the PAG may elicit the involvement of noradrenergic systems in distant brain regions in the mediation of analgesia.
D000698:Analgesia; D000818:Animals; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry / Q000187:drug effects; D002540:Cerebral Cortex / Q000378:metabolism; D007276:Injections, Intraventricular; D007981:Levorphanol / Q000494:pharmacology; D008032:Limbic System / Q000378:metabolism; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000378:metabolism; D009020:Morphine / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D007981:Levorphanol; C030284:3-methoxy-4-hydroxyphenylglycol sulfate; D008734:Methoxyhydroxyphenylglycol; D009020:Morphine; D009638:Norepinephrine