The interaction of peripherally and centrally administered dexamethasone and RU 38486 on morphine analgesia in mice.
1. Dexamethasone or RU 38486 were administered intraperitoneally or intracerebroventricularly to mice 10 or 120 min before morphine administration. The interaction of these drugs with the analgesic effects of morphine was examined using the hot plate test. 2. Dexamethasone i.p. pretreatment reduced analgesic responses to morphine injected 120 min but not 10 min after dexamethasone; i.c.v. injection of dexamethasone 10 and 120 min before morphine administration was effective in reducing morphine analgesia. 3. RU 38486 i.c.v. pretreatment (but not i.p. pretreatment) performed 120 (but not 10) min before morphine administration enhanced morphine analgesic effects. 4. These results, particularly the effects of drug interaction for i.c.v. administration, strongly confirm a central site for dexamethasone and RU 38486 action.
Pieretti
S
S
Istituto Superiore di Sanità, Laboratorio di Farmacologia, Rome, Italy.
Capasso
A
A
Di Giannuario
A
A
Loizzo
A
A
Sorrentino
L
L
D000698:Analgesia; D000818:Animals; D003907:Dexamethasone / Q000008:administration & dosage / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D015735:Mifepristone / Q000008:administration & dosage / Q000494:pharmacology*; D009020:Morphine; D010146:Pain / Q000503:physiopathology; D010147:Pain Measurement; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors; D012684:Sensory Thresholds / Q000187:drug effects
D011965:Receptors, Glucocorticoid; D015735:Mifepristone; D009020:Morphine; D003907:Dexamethasone