Involvement of Serotonin 5-HT7 Receptors in Learning and Memory in Mice

Serotonin (5-HT) is involved in memory processing via different types of its receptors within brain regions. We investigated the role of 5-HT7 receptors in acquisition, consolidation, and retrieval phases in the passive avoidance (PA) learning and memory test in mice. Adult male mice (body mass 20-35 g) were randomly divided into four experimental groups (n = 10 in each). Animals of the control group received saline, while other groups of mice received SB-269970 (a selective 5-HT7 receptor antagonist, 10 mg/kg, i.p.) 15 min before training, immediately after training, and 24 h after the acquisition trial. Numbers of trials to acquisition (NT), initial entry latency into the dark compartment in the learning phase, step-through latency, and time of stay in the dark compartment in the retention phase of the PA test (STLr and TDC, respectively) were measured. The number of trials to acquisition in the group receiving SB-269970 before training showed no significant differences in comparison with the control group. The STLr in the group receiving SB-269970 after training was significantly greater, while its TDC was shorter than in the control. There were no significant differences in the STLr and TDC between the control and SB-269970 group receiving the blocker before retrieval. It is concluded that blocking of 5-HT7 receptors could improve consolidation of the passive avoidance memory, but this procedure exerted no significant effects on acquisition and retrieval in the PA test.