Independent central and peripheral mediation of XXXX -induced inhibition of gastrointestinal transit in @entity35 .

@entity836 @entity1337 @entity25716 @entity1286 @entity35
The individual contributions of central (brain) and peripheral (enteric) sites in the mediation of the systemic actions of opioids are not well established. In this study, we made use of @entity25716 , a quaternary analog of @entity836 , to separate the central and peripheral components of the slowing action of @entity1286 on gastrointestinal transit in @entity35 . It was established that i.c.v., but not s.c., administration of quaternary @entity836 antagonized @entity1286 -induced @entity1337 in the radiant-heat tail-flick assay in @entity35 . Thus, quaternary @entity836 probably does not enter the central nervous system in significant amounts after systemic administration. Systemic quaternary @entity836 antagonized, in a dose-related manner, the delaying effects of @entity1286 on the movement of a charcoal meal along the gastrointestinal tract. Quaternary @entity836 was 30 or 100 times less potent than @entity836 when administered s.c. or i.c.v., respectively. Unlike @entity836 , quaternary @entity836 antagonized @entity1286 -induced slowing of gastrointestinal transit only when administered by the same route (i.e., both s.c. or both i.c.v.). The apparent pA2 for s.c. quaternary @entity836 against s.c. @entity1286 was not significantly different from the apparent pA2 for i.c.v. quaternary @entity836 against i.c.v. @entity1286 . Distinct and independent central and peripheral systems appear to mediate @entity1286 -induced inhibition of gastrointestinal transit in @entity35 . However, the receptors are probably of the same type. Peripherally selective antagonists such as quaternary @entity836 may be useful in reversing @entity1286 -induced inhibition of gastrointestinal transit without affecting @entity1337 .
