Abstract: Population spikes(PS) were recorded from dentate gyrus(DG)of freely moving rats following stimulation of the perforant path. The rats were trained to perform conditioned drinking behavior.(1)High-frequency stimulation(HFS) of the mammillary body(MB) could elicit a temporary inhibition of PS in DG.(2)Animals were treated with HFS of MB before daily trai ning session,the development of learning-dependent long-term potentiation(LDLTP)was depressed significantly, and the establishment of conditioned response was suppressed parallelly,(3)The inhibitory effect of HFS of MB on PS in DG was weakened significantly as the enhancement of PS amplitude reached the maximal level.(4)HFS of MB had no clear effect on the retention of LDLTP and the consolidation of conditioned response.The results suggested that MB might exert an inhibitory modulation on the development of LDLTP in DG.

Key words: long-term potentiation, learning, memory, hippocampus, mammillary body