The influence of naloxone on the effects of adenosine receptor agonists in analgesic tests and binding studies.
Naloxone (1 mg/kg ip) reduced analgesic effect of R-phenylisopropyladenosine (R-PIA-0.2 mg/kg sc) in hot plate and tail-immersion tests in mice and in tail-immersion test in rats. Also the effect of 2-chloroadenosine (2-CADO-2 mg/kg sc) was significantly reduced by naloxone in mice in both nociceptive tests. Naloxone induced partial reduction of analgesic effects of 5'-N-ethylcarboxamideadenosine (NECA-0.02-0.05 mg/kg sc) in mice and rats. Binding studies revealed that the affinity of adenosine agonists (R-PIA and NECA) to opioid receptors was about 5000 times weaker than the corresponding affinity of naloxone.
Michalska
E
E
Department of Pharmacodynamics, Medical Academy, Lublin, Poland.
Malec
D
D
Antkiewicz-Michaluk
L
L
D015762:2-Chloroadenosine / Q000037:antagonists & inhibitors / Q000378:metabolism; D000241:Adenosine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism; D019830:Adenosine-5'-(N-ethylcarboxamide); D000698:Analgesia; D000818:Animals; D001921:Brain / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D008297:Male; D051379:Mice; D009270:Naloxone / Q000378:metabolism / Q000494:pharmacology*; D010660:Phenylisopropyladenosine / Q000037:antagonists & inhibitors / Q000378:metabolism; D058906:Purinergic P1 Receptor Agonists; D051381:Rats; D017208:Rats, Wistar; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism
D058906:Purinergic P1 Receptor Agonists; D011957:Receptors, Opioid; D015762:2-Chloroadenosine; D010660:Phenylisopropyladenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); D009270:Naloxone; D002110:Caffeine; D000241:Adenosine