塩化リチウム注射によるラット（Rattus norvegicus）のカオリン粘土摂取行動の時間的推移

抄録

Pica, the ingestion of non-nutritive substances, is widely used as an index of nausea in rats, which are physiologically incapable of vomiting. Administration of lithium chloride (LiCl) reliably generates kaolin clay consumption and serves as a standard marker of nausea. However, most previous studies have reported only daily totals of kaolin intake, leaving its temporal dynamics unclear. The present study examined whether hourly measurements of kaolin consumption could reveal the time course of LiCl-induced nausea. In Experiment 1, LiCl was administered near the end of the light phase; rats began consuming kaolin within 1 hour, with intake peaking during the subsequent dark phase. In Experiment 2, LiCl was administered earlier in the light phase; kaolin intake was minimal during the light phase but increased markedly after the onset of darkness. Across experiments, kaolin intake was modulated by circadian feeding rhythms. These findings suggest that temporal patterns of pica reflect not only nausea but also circadian factors.