The Effect of Ketanserin and Pirenperone Injected into the CA1 Region on Spatial Discrimination

In the present study, the effect of 5-HT2A receptor blockers in CA1 region of rat hippocampus on spatial learning was assessed in a T-maze, a spatial discrimination task. Rats were canulated bilaterally and injected daily vehicle (saline), 5-HT2A-selective antagonist, ketanserin (0.6, 1.2 or 2.4 µg/0.5 µl) and pirenperone (0.1, 0.3, 1.2 or 2.4 µg/0.5 µl) into the cannula 30 minutes before training. Results indicated that ketanserin and pirenperon did not affect spontaneous alternation and also did not induce a significant effect on trials to reach criterion and errors made by animals throughout spatial discrimination and reversal learning. But, in the rats that received ketanserin produced dose dependent decrease in the latencies to enter the chosen arm in both learning and reversal stages. During extinction, no change was observed in the choice of the previously reinforced arm in both ketanserin and pirenperone groups. The slope of latency in the ketanserin group that had received the highest dose of ketanserin (2.4 µg) than the sham operated group but not in the pirenperone group. These findings suggest that 5-HT2A receptors blockade (ketanserin, but not pirenperone) in the CA1 region may decrease decision time and increase behavioural flexibility in T-maze.