Effect of opioid peptides on L-noradrenaline-stimulated cyclic AMP formation in homogenates of rat cerebral cortex and hypothalamus.
Morphine and the opioid peptides leucine-enkephalin (leu-enk), methionine-enkephalin (met-enk) and beta-endorphin had no effect on basal cyclic AMP levels in rat cerebral cortex and hypothalamus, but each inhibited noradrenaline (NA)-stimulated cyclic AMP formation in both brain regions. This inhibition was reversed by naloxone. Naloxone did not reverse phentolamine- or propranolol-induced inhibition of NA-stimulated cyclic AMP formation. The increase in cyclic AMP formation induced by NaF or MnCl2 was unaffected by met-enk or morphine. These data suggest that in rat cerebral cortex and hypothalamus opiates bind to opiate receptors and that the opiate-receptor complex interferes with noradrenergic receptor activity.
D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D000242:Cyclic AMP / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D012964:Sodium / Q000494:pharmacology
D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone; D009020:Morphine; D012964:Sodium; D000242:Cyclic AMP; D009638:Norepinephrine