Influence of omega-conotoxin on morphine analgesia and withdrawal syndrome in rats.
The effect of omega-conotoxin on opiate analgesia and withdrawal syndrome was investigated in rats. omega-Conotoxin given i.c.v. and i.p. caused weak analgesia in the tail-flick test. When the toxin (20 ng/rat) was given i.c.v. immediately before morphine (1.5 micrograms/rat i.c.v.) the resultant analgesic effect was additive. In contrast, the analgesia elicited by morphine (3 micrograms/rat i.c.v.) was greatly reduced after 24-h pretreatment with the toxin (20 ng/rat i.c.v.). The systemic administration of the toxin (10 micrograms/kg i.p.) did not affect morphine analgesia whether omega-conotoxin was coadministered with morphine (2.5 mg/kg i.p.) or was given 24 h before the opiate (5 mg/kg i.p.). omega-Conotoxin i.c.v. injected in morphine-dependent rats 15 min before naloxone challenge significantly attenuated the abstinence syndrome. On the contrary systemic administration of omega-conotoxin failed to suppress the morphine withdrawal syndrome. The present results suggest that omega-conotoxin affects both acute and chronic effects of morphine.
Basilico
L
L
Institute of Pharmacology, Faculty of Sciences, University of Milan, Italy.
Parolaro
D
D
Rubino
T
T
Gori
E
E
Giagnoni
G
G
D000698:Analgesia; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects; D005260:Female; D008978:Mollusk Venoms / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology*; D051381:Rats; D013375:Substance Withdrawal Syndrome / Q000517:prevention & control*; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D008978:Mollusk Venoms; D010456:Peptides, Cyclic; D020960:omega-Conotoxins; C053423:Conus magus toxin; D009270:Naloxone; D009020:Morphine; D002118:Calcium