Central versus peripheral effects of scopolamine on performance in a delayed simple discrimination tas

Abstract

As an_ amnestic agent, scopolamine hydrobromide (SHB) has been used as· a classic model for amnesia. While it is generally accepted that SHB affects stimulus discrimination, attention, and acquisition, a conflict exists ~s to whether the time-dependent process of retention is affected by scopolamine. Wis tar rats were trained in·a simple discrimination task with tone and light stimuli and with delays of increasing length interposed between the stimulus and ,the response. When the rats were well-trained, 4 doses (5, 10, 25, and 50 μg/kg) of $HB and of scopolamine methylbromide (SMB), a quaternary analog that does not easily enter the CNS, were injected subcutaneously once or twice weekly before the daily session. With light as the stimulus, there were significant dose and delay effects .with both drugs and no difference in the effects of the two drugs except for a trend toward a greater effect of scopolamine hydrobromide on accuracy at the highest dose.