Effect of scopolamine on hidden- and visible-water maze learning and retention trial performance in C57BL mice

The Morris water maze is one of the most extensively used tools in behavioral neuroscience to investigate spatial learning and memory [1]. MWM learning is thought to rely extensively on hippocampus, and involves several major neurotranmitter systems. One such major neurotransmitter system of great importance is the cholinergic system [2]. Scopolamine, a muscarinic cholinergic antagonist, is known to cause impairments in MWM testing [1]. Studies have suggested that scopolamine administration specifically impairs the development of spatial navigation strategies, thus the acquisition, rather than memory consolidation or recall [2,5]. Day and Schallert hypothesized that acquisition impairment, following anticholinergic treatmentis mediated at least partially by entrapment in an inefficient, non-place strategies [3]. The present study investigates the effect of scopolamine in MWM. Subjects were trained during 10 trialblocks, each of which consisted out of 4 trials. After the fifth and the tenth training trial, animals were tested (probe trial of 100s). Animals (n=4) were injected with scopolamine (1mg/kg), 30 minutes prior to performance. Animals (n=4) injected with saline (10ml/kg) served as controls. To examine whether the impairment is due to deficits in acquisition or recall, we injected control animals (n=2) with scopolamine (1mg/kg) 30 minutes before the second probe trial. In another trialblock all animals (n=8) received saline injections (10ml/kg).