Evaluation of endomorphin-1 on the activity of Na(+),K(+)-ATPase using in vitro and in vivo studies.
The goal of this study was to investigate the effects of endomorphin-1 on Na(+),K(+)-ATPase activity in mouse brain synaptosome in vitro, and its antinociceptive interaction with the Na(+),K(+)-ATPase inhibitor ouabain. Endomorphin-1 (0.1 nM-10 microM) produced a concentration-dependent (EC(50): 43.19 nM, CI: 23.38-65.71 nM, E(max): 25.86%, CI: 24.53-27.20%), naloxone-reversible increase of the synaptosomal Na(+),K(+)-ATPase activity. The intrathecally (i.t.) administered endomorphin-1 (2-20 microg) produced a dose-dependent short-lasting increase in the tail-flick latency. Ouabain itself (1-1000 ng, i.t.) did not cause antinociception. Treatment with 10 ng ouabain significantly decreased the antinociceptive effect of 2 microg endomorphin-1, but none of the other combinations did significantly differ from the endomorhin-1-treated groups. These data indicate that endomorphin-1 increases the activity of Na(+),K(+)-ATPase in vitro but this effect may play a weak role in the antinociception induced by intrathecal endomorphin-1.
Horvath
Gyöngyi
G
Department of Physiology, Faculty of Medicine, University of Szeged, Szeged, Hungary. horvath@phys.szote.u-szeged.hu
Agil
Ahmad
A
Joo
Gabriella
G
Dobos
Ildikó
I
Benedek
György
G
Baeyens
Jose Manuel
JM
D000700:Analgesics / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D010042:Ouabain / Q000494:pharmacology; D010146:Pain / Q000517:prevention & control; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects* / Q000201:enzymology; D013997:Time Factors
D000700:Analgesics; D000701:Analgesics, Opioid; D004791:Enzyme Inhibitors; D009842:Oligopeptides; C105293:endomorphin 1; D010042:Ouabain; D009020:Morphine; D000254:Sodium-Potassium-Exchanging ATPase