Scopolamine induced non-cognitive effects in the radial-arm maze: Alleviation by physostigmine

Document Type : Original Article



Purpose: Scopolamine has frequently been reported to induce a “memory deficit” in animals and humans. However, the possible role of the non-cognitive effects of the drug in these impairments is often ignored. In the present study, the effects of scopolamine on various behaviors in the radial arm maze were recorded and the ability of physostigmine to reverse them was examined.
Methods: Male Long-Evans hooded rats were trained on an 8-arm radial maze to consume drops of 0.1 ml of sweetened milk from the end of each arm. Once the asymptomatic performance was achieved, the effects of scopolamine (0.25 mg/kg i.p. 20 min before testing) on(1) the number of errors (re-entries into the arms), (2) the number of rewards drops not consumed, and (3) agitation were examined.
Results: The number of errors, the number of drops left, and agitation scores were increased significantly compared to saline-treated rats. Concomitant administration of scopolamine and physostigmine (0.25 i.p. 15 min before testing) significantly reduced the agitation scores and revealed a trend toward a decrease in the number of drops left compared to scop-treated rats. However, in this experiment, scopolamine did not significantly increase the number of errors compared to the saline-treated rats.
Conclusion: Taken together, scopolamine induced a small but inconsistent increase in the number of errors. In contrast, there were significant effects of scopolamine on agitation and milk consumption in both experiments. These non-cognitive effects of scopolamine (which were attenuated by physostigmine) may indirectly lead to an increase in errors.