Ondansetron blocks nifedipine-induced analgesia in rats.
The serotonergic system is involved in pain transmission and the 5-hydroxytryptamine (5-HT3) receptor subtype mediates some of these effects at the spinal level. Therefore, we explored the effects of the serotonergic system on nifedipine-induced analgesia by using the 5-HT3 receptor antagonist ondansetron. Male Sprague-Dawley rats were pretreated with ondansetron (1 mg/ kg intraperitoneally) or normal saline. After 15 min, rats received injections of nifedipine (15 mg/kg intraperitoneally) or dimethylsulfoxide (DMSO), solvent for nifedipine, as a control. Nociception was assessed by tail-flick method. Rats treated with nifedipine alone had an increase in tail-flick latency of 122%, as measured by the area under the curve, compared to rats treated with DMSO alone. Pretreatment with ondansetron, however completely blocked the analgesic effect of nifedipine, with tail-flick latency remaining at baseline throughout the measurement period. These results indicate that the 5-HT3 receptor plays an important role in the analgesic response to nifedipine and that medications that block this receptor may decrease the analgesic effectiveness of this type of therapy.
Hunt
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TE
Department of Anesthesiology, University of Medicine and Dentistry of New Jersey, Newark, USA.
Wu
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W
Zbuzek
V K
VK
D000698:Analgesia; D000700:Analgesics / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D000818:Animals; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D008297:Male; D009543:Nifedipine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D017294:Ondansetron / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology; D017288:Pain Threshold / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D012702:Serotonin Antagonists / Q000494:pharmacology*
D000700:Analgesics; D012702:Serotonin Antagonists; D017294:Ondansetron; D009543:Nifedipine; D004121:Dimethyl Sulfoxide