Prolonged in vivo antagonism of central mu- and delta-opioid receptor activity by beta-funal trexamine.
beta-Funaltrexamine (beta-FNA) was tested in the spinal cord and supraspinally against inhibition of reflex bladder contractions produced in the anesthetized rat by the opioid-receptor selective agonists [D-Ala2, MePhe4, Gly (ol)5]enkephalin (DAGO, mu-agonist) and [D-Pen2, D-Pen5] enkephalin (DPDPE, delta-agonist). All agents were microinjected either intracerebroventricularly (i.c.v.) or intrathecally (i.t.). beta-FNA (1-8 micrograms) produced long-lasting antagonism of both DAGO and DPDPE. Complete recovery from its effects was only observed some 24-32 h later. Higher doses of beta-FNA (4 and 8 micrograms i.t.) produced short-lived agonistic activity though the selectivity of this was not determined. It was concluded that beta-FNA was a potent, long-lasting antagonist at central opioid receptors in vivo but was unselective for the mu and delta opioid receptor.
Dray
A
A
Nunan
L
L
Wire
W
W
D000818:Animals; D005260:Female; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D009119:Muscle Contraction / Q000187:drug effects; D009270:Naloxone / Q000031:analogs & derivatives*; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects*; D001743:Urinary Bladder / Q000187:drug effects
D011957:Receptors, Opioid; D009270:Naloxone; D009271:Naltrexone; C024524:beta-funaltrexamine