• T E Hunt, W Wu, and V K Zbuzek.
• Department of Anesthesiology, University of Medicine and Dentistry of New Jersey, Newark, USA.
• Anesth. Analg. 1996 Mar 1;82(3):498-500.

AbstractThe 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.

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