Plasma norepinephrine, epinephrine and dopamine responses to intracerebral administration of a met-enkephalin analog, D-ala2-met-enkephalinamide, in rats.
Intracisternal (i.c.) administration (25 microgram or 42.6 nmol) of the potent met-enkephalin analog, D-ala2-met-enkephalinamide (DALA) in adult male rats increased plasma concentrations of norepinephrine and epinephrine for more than 90 min. Intra-arterial (i.a.) administration of the same or a fourfold larger dose was without any effect. I.c. administration of human beta-endorphin (25 microgram or 7.25 nmol) produced much greater plasma responses of all three catecholamines than seen with DALA. An i.a. dose of naloxone, which had been shown previously to inhibit the plasma catecholamine responses to beta-endorphin, failed to inhibit plasma catecholamine responses to DALA. Also, naloxone alone failed to alter the basal plasma concentrations of the three catecholamines. The data are consistent with an effect of DALA acting at a presently unknown brain site to increase central sympathetic outflow, thus increasing plasma concentrations of norepinephrine and epinephrine. It appears probable that this effect of DALA is mediated at a different opioid receptor and perhaps a different brain site than the effect of beta-endorphin to increase central sympathetic outflow.
D000818:Animals; D002946:Cisterna Magna; D004298:Dopamine / Q000097:blood*; D004723:Endorphins / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives*; D004745:Enkephalins / Q000494:pharmacology*; D004837:Epinephrine / Q000097:blood*; D007267:Injections; D007269:Injections, Intra-Arterial; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009638:Norepinephrine / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin
D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; C022118:enkephalinamide-Met, Ala(2)-; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine