Effect of prior experience of an environment on scopolamine-induced changes in activity

Rats were given 0 or 30 min prior experience of a 36 in. x 36 in. open field then injected with saline or 0.25 or 4.0 mg/kg scopolamine before being tested in the field for 15 min. With no prior experience both doses of scopolamine produced equivalent increases in ambulation and 4.0 mg/kg increased rearing but neither dose affected grooming; however, with experience scopolamine increased ambulation and rearing in a dose-related way and produced equivalent increases in grooming. The resulting level of ambulation and rearing produced by 4.0 mg/kg was, however, higher and that of 0.25 mg/kg lower (for ambulation) in the experience condition compared to that in the no experience condition. These effects could partly be attributed to a decreased level of each response in the undrugged animals in the experience condition. It was concluded that prior experience of an environment does change scopolamine-induced effects on activity.