Inhibition of noradrenaline release from cerebrocortical synaptosomes and stimulation of synaptosomal Na+,K(+)-ATPase activity by morphine in rats.
The effects of morphine on noradrenaline (NA) release from rat cerebrocortical synaptosomes and on the synaptosomal Na+,K(+)-ATPase activity were determined. Morphine (10(-3)-10(-5) M) caused a dose-related inhibition of enhanced prelabelled [3H]NA release evoked by a high concentration of K+ from synaptosomes and this inhibitory action of morphine was antagonized by the specific antagonist naloxone (10(-4), 10(-5) M). Morphine dose-dependently stimulated the synaptosomal Na+,K(+)-ATPase activity but not Ca2(+)-ATPase activity in the incubation medium containing 2.2 x 10(-6)-4.7 x 10(-7) M free Ca2+, and this stimulatory effect was antagonized by naloxone. These results suggest that morphine may have some role in the suppression of membrane depolarization and/or the release of NA through its stimulatory action on the Na+,K(+)-ATPase activity in rat cerebral cortex.
Nishikawa
T
T
Department of Pharmacology, Kagoshima University Dental School, Japan.
Shimizu
S
S
D000818:Animals; D002540:Cerebral Cortex / Q000201:enzymology / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013570:Synaptic Membranes / Q000201:enzymology; D013574:Synaptosomes / Q000201:enzymology / Q000378:metabolism*
D009270:Naloxone; D009020:Morphine; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D009638:Norepinephrine