Insulin attenuates scopolamine-induced memory deficits

Most of the agents that attenuate scopolamine-induced amnesia can also improve memory when injected alone. We report here that insulin can attenuate scopolamine-induced amnesia even though insulin per se has little memory-improving action. Male Balb/c mice were trained in an appetitive barpressing task. Immediately after the mice had completed 15 trials, scopolamine hydrochloride was injected (0.1, 0.2, 0.3, 0.6, 1.0 mg/kg i.p.) in conjunction with either saline or insulin (0.8 IU/kg, subcutaneously). The animals’ retention of the training was tested the next day. The 0.6- and 1.0-mg/kg doses of scopolamine (but not the lower doses) produced an amnesia for the barpressing task training. This amnesia was significantly reduced by an insulin injection given at the same time as the scopolamine injection. However, the injection of insulin alone had no effect on memory processes. These results show that insulin can protect from scopolamine amnesia. Possibly, insulin modulates scopolamine-induced amnesia directly through an action on insulin receptors in the brain.