Scopolamine-induced cognitive impairment needs a steady does of a long-term administration to be indicative of remarkable spatial memory deficits that could be assessed by MWM for instance.

I think that it is OK to see no significant deterioration in memory of scopolamine-treated rats after only 5 days even up to 10 days. This depends on the dose per kg that you administer and the concentration of scopolamine solution that you prepared before injection (scopolamine to solvent ratio such as DMSO, etc.).

I would recommend to administer scopolamine at a dose of 1 mg/kg for 15 days and see if your impaired rat group would show significant signs of memory deficits duing the MWM testing phase.

If you do not see such deterioration in spatial memory, then check the concentration of scopolamine solution first, and afterwards increase the concentration and scopolamine dose per kg accordingly.

I agree with the above answer, but much too often I have seen water maze setups that are not optimized for the task. Make sure you are using spatial cues on each side of the room and not inside the maze itself, followed by lights that are also symmetrical.

Thanks so much :)