Differential action of ondansetron and dexamethasone to modify cisplatin-induced acute and delayed kaolin consumption ("pica") in rats.

The ability of cisplatin to induce acute (0-24 h) and delayed (24-48 and 48-72 h) phases of kaolin ingestion (pica) was investigated in the rat. Cisplatin 3 mg/kg, i.p., induced kaolin consumption during the 0-24- (P<0.001) and 48-72-h (P<0.05) periods that was antagonised by dexamethasone 1 mg/kg, i.p., administered every 12 h alone or in combination with ondansetron 2 mg/kg, i.p., administered every 12 h (P<0.05). As a single treatment, ondansetron 2 mg/kg, i.p., administered every 12 h potentiated cisplatin-induced kaolin consumption by 41% (P<0.05) during the 0-24-h period but had no action to modify the delayed response (P>0.05). Dexamethasone 1 mg/kg, i.p., administered every 12 h and cisplatin 3 and 6 mg/kg, i.p., but not ondansetron 2 mg/kg, i.p., administered every 12 h (P>0.05) reduced food consumption and decreased rat weight. The highest dose of cisplatin 6 mg/kg, i.p., induced acute (P<0.001) but not delayed kaolin ingestion (P>0.05). The action of cisplatin to induce acute and delayed pica is complicated and may be affected by drugs that modify appetite.