Differential effects of kainic-acid-induced hippocampal lesions on the acquisition of the jump-box avoidance task in mice.

This research examined the effects of kainic-acid (KA)-induced hippocampal lesions on the acquisition of a jump-box avoidance task in mice. When the hippocampal lesion was unilateral, mice with lesions in the lateral portion of the CA1 region showed deficits in acquisition while those with lesions in the CA3 region and/or the medial portion of the CA1 region did not. When the hippocampal lesion was bilateral, on the other hand, mice with lesions in the CA3 region and/or the lateral portion of the CA1 region were deficient in acquisition while those with lesions in the medial portion of the CA1 region were not. Among the mice with various KA-induced hippocampal lesions avoidance responses were not correlated with the level of open field activity, indicating that acquisition differences observed are not dependent upon, nor secondary to, levels of spontaneous activity. These results strongly suggest that there exist regional differences in the involvement of hippocampal pyramidal cell layers in acquisition of the jump-box avoidance task: both the CA3 region and the lateral portion of the CA1 region are involved in acquisition, while the medial portion of the CA1 region is not.