The changes in active avoidance response following rivastigmine ve memantine treatment in rats with lesions in bilateral hippocampal formation

To determine the effects of bilateral hippocampal lesion on the active avoidance response and to examine the changes in active avoidance following treatment with an acetylcholine esterase inhibitor rivastigmine and a NMDA receptor antagonist memantine. The study performed in seven groups of male wistar rats (250-350). In first three group bilateral ventral hippocampal lesions were produced by injecting quinolinic acid stereotacticly. Sham operation was performed in the fourth group. The three groups with bilateral hippocampal lesion were injected with saline, rivastigmine and memantine, respectively. Saline was given to the sham group. Another three control group were composed and given saline, rivastigmine ve memantine. Active avoidance response was measured using shuttle-box. The changes in learning of avoidance among the groups were determined by using Kruskal Walles and Mann-Whitney U test. Freidman test was also used to determine time-response of learning of avoidance for each rat. H&E staining was performed in the coronal sections of the brains in order to varify the presence of ventral hippocampal lesions. Bilateral lesions of the ventral hippocampus did not alter the active avoidance response when compared to sham group. In all groups there was a significant increase in learning of active avoidance with time in 5 days (Freidman test, p<0.05). There was, however, no difference in active avoidance with time in the animals treated with rivastigmine or memantine (Freidman testi, p>0.05). These findings demonstrate bilateral hippocampal lesions do not affect active avoidance response. These results support the idea that active avoidance response is an implicit learning and is independent from hippocampus. Altered active avoidance response following treatment with acetylcholine esterase inhibitor or NMDA receptor antagonist in rats with hippocampal lesions also suggests that this is an implicit learning and these drugs alter learning by affecting other systems related with implicit learning such as basal ganglia and cerebellum.