Cork gnawing in the rat as a screening method for buspirone‐like anxiolytics

Male Long‐Evans rats were individually allowed access to No. 11 corks for 30 min per day. After 30 sessions, the mean amount gnawed away, 0.10 g per session, was stable enough to allow drug testing; it reached asymptote at 0.03 g after 140 sessions. Drugs were injected PO 30 min before testing, except as noted. On the asymptotic baseline, the novel anxiolytic buspirone (8–32 mg/kg) and its congener gepirone (8–32 mg/kg) produced large, doserelated increases in cork gnawing. The standard anxiolytics chlordiazepoxide (16–32 mg/kg) and meprobamate (128 mg/kg, 60 min pretreatment) and the new sedative zopiclone (4–32 mg/kg) also produced substantial increases. Diazepam, oxazepam, and alprazolam produced marginal increases, and pentobarbital had no effect at behaviorally relevant doses. The non‐anxiolytics d ‐amphetamine, chlorpromazine, acute imipramine, morphine (IP), and valproic acid either decreased or did not change cork gnawing. Phencyclidine (IP) and scopolamine produced marginal increases. Apomorphine (5 mg/kg SC) produced intense stereotyped gnawing of cage mesh but abolished gnawing of cork. Cork gnawing is proposed as a simple, economical behavioral method to identify buspirone‐like anxiolytics.