Electrophysiological characterization of associational pathway terminating on dentate gyrus granule cells in the rat.

The functional topography and parameters of excitation and inhibition were determined in the in situ associational pathway of the rat dentate gyrus. The functional topography was found to be consistent with previous anatomical studies. The greatest amplitude population spikes and the strongest paired-pulse inhibition were generated with the stimulating electrode placed in the hilus at least 1.5 mm caudal to the ipsilateral dentate gyrus recording electrode. With this standard electrode configuration, neither long-term potentiation of the population spike nor of the population excitatory postsynaptic potential occurred. Hilar associational pathway activation of dentate gyrus granule cells elicited paired-pulse responses similar to those produced in granule cells by perforant path stimulation. Thus, the associational pathway provides another way to assess dentate granule cell function electrophysiologically.