Time-course analysis of pica in rats using an automatic feeding monitoring system.

INTRODUCTION

We have reported that pica, kaolin ingestion behavior, correlates with nausea and vomiting in rats and the amount of kaolin intake is related to the severity of symptoms. However, the time course of the behavior is still unclear, because kaolin intake has been measured 24h after administration of an emetic stimulus. It is quite difficult and troublesome to determine kaolin intake manually at short time intervals without affecting the animal's behavior. In the present study, we investigated the time course of radiation or chemotherapeutic agent-induced pica in rats using an automatic feeding monitoring system (FDM700SW).

METHODS

Rats received total body X-ray irradiation (4 Gy), or i.p. administration of cisplatin (6 mg/kg) or cyclophosphamide (120 mg/kg) with or without pretreatment of 5-HT(3) receptor antagonist, granisetron (0.1mg/kg, i.p.), then their kaolin and food intake were monitored hourly for 24h after the emetic stimuli.

RESULTS

Total body irradiation and i.p. injection of cisplatin or cyclophosphamide induced pica within 3h of the administration and the pica persisted for 12, 8 and 16 h after the emetic stimuli, respectively. Granisetron delayed the latency and inhibited the amount of kaolin intake. X-ray and chemotherapeutic agents induced anorexia in all rats, but anorexia was not recovered by pretreatment with granisetron.

DISCUSSION

These results suggested that both the latency and the duration of pica are similar to the clinical evidence of radiation or chemotherapy-induced nausea and vomiting in human patients and this monitoring system is useful to evaluate the emetogenic potential of drugs and other medical intervention in preclinical studies.