Abstract: The changes and their interrelations of synaptic transmission inboth CA_3 and dentate gyrus(DG) of rat hippocampus during discri-mination learning were observed in order to investigate the charac-teristics and mutual relations of the changes of synaptic plasticityin different hippocampal areas with the processing of learning. (1)Population spike(PS) in the CA_3 and DG were simultaneously elici-ted by stimulating the perforant path (PP). The amplitude of PSincreased in response to a series of increases of the stimulation in-tensity, but the increase of amplitude of PS in the DG was lessthan in the CA_3 area. (2)The learning-dependent long-term potentia-tions(LDLTP) in the CA_3 and DG were induced simultaneously withthe acquisition of the behavioral response. There was a significantpositive relation during the developing of LDLTP in the two areas(R=0.9806, p<0.01). Both maximal level of amplitude of PS in CA_3and DG preceded those of the correct behavior response. Resultsshowed that LDLTP of the synaptic transmission of PP-CA_3 andPP-DG were simultaneously produced during the discrimination learn-ing, and provided a new way to record and analyse at the same time thechanges and their correlation of synaptic transmission between thetwo hippocampal areas under the situation of chronic recording.

Key words: learning, hippocampus, synaptic plasticity, long-term potentiation