Naloxonazine and opioid-induced inhibition of reflex urinary bladder contractions.
Spontaneous volume-induced contractions of the urinary bladder were recorded isometrically in urethane-anesthetized rats. Contractions were inhibited by alternate submaximal but equieffective doses of the selective mu and delta-opioid ligands [D-Ala2-Me-Phe4,Gly(ol)5] enkephaline (DAGO) and [2-D-penicillamine, 5-D-penicillamine] enkephalin (DPDPE), respectively, administered by the intracerebroventricular (i.c.v.) or spinal intrathecal (i.t.) route. Naloxonazine, postulated to be an irreversible mu 1-opioid receptor antagonist, administered by the same route, antagonized the effects of both DAGO and DPDPE. The antagonism of the effect of DAGO was reversed 3-4 hr later but that of DPDPE was more prolonged. Recovery of the effect of DPDPE was observed some 24 hr later. A similar pattern of activity against DAGO and DPDPE given intraventricularly or intrathecally was observed following intravenous injection of naloxonazine (10 mg/kg). Also naloxonazine (i.c.v., i.t. or i.v.) antagonized the effect of morphine given intraventricularly or intrathecally, but antagonism was not observed when morphine was retested 3-4 hr and 24 hr later. Naloxonazine increased the frequency of contraction of the bladder after each route of administration. This effect lasted 1-3 hr and was not seen 24 hr later. Systemic administration of naloxone (10 mg/kg, i.v) also increased the frequency of bladder contraction and attenuated or abolished the effect of DAGO given intraventricularly or intrathecally and the delta-receptor agonist [2-D-penicillamine, 5-L-penicillamine] enkephaline (DPLPE).(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009270:Naloxone / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects*; D012018:Reflex / Q000187:drug effects*; D001743:Urinary Bladder / Q000294:innervation* / Q000502:physiology
D004745:Enkephalins; D011957:Receptors, Opioid; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009270:Naloxone; C034643:naloxonazine; D020881:Enkephalin, D-Penicillamine (2,5)-