The durations of hippocampal and cortical cholinergic activation induced by spatial discrimination testing of mice in an eight-arm radial maze decrease as a function of acquisition.

Sodium-dependent high-affinity choline uptake velocities in P2 fractions of the hippocampus and cortex of mice were analyzed at different times following both the first (Day 1) and last (Day 9) daily sessions of a spatial discrimination testing procedure in an eight-arm radial maze. Results showed that the immediate (30 s) post-training increase in mean hippocampal and cortical cholinergic activity observed on Day 1 did not significantly vary over days despite a marked and progressive improvement of discrimination performance. In contrast, the duration of these activations was considerably shortened in both structures between Days 1 (more than 1 hr) and 9 (about 15 min). The possible involvement of these changes in memory consolidation processes is discussed.