Scopolamine suppresses both locomotion and object contact in a free-exploration situation.

It was recently reported by Buhot et al. that presession cholinergic disruption with scopolamine decreases time spent in proximity to novel objects while increasing locomotor behavior. Male Long-Evans rats (Rattus norvegicus, 80 days old) were given low-light access to an arena containing objects but were not forced to remain in the arena. On day 1, each subject was injected with saline (SAL). This session was used for familiarization with the apparatus and procedure. On days 2 and 3, four groups were given saline (SAL) or scopolamine (SCO, 1 mg/kg or 0.25 mg/kg), resulting in SAL-SAL, SAL-SCO, SCO-SAL, and SCO-SCO groups. Videotapes of these sessions were scored according to a standard protocol that allows separate quantification of locomotion, general activity, and object interaction behaviors. Scopolamine suppressed object investigation (both gross contact measures and indices of interaction character) whenever present. In contrast to Buhot et al. (using a forced-exploration situation), in this free-exploration context SCO also suppressed locomotor behavior. This study supports the conclusion that anticholinergics impair information gathering instead of affecting memory directly, which calls into question memory-related explanations of cholinergic treatments.