Depotentiation in the dentate gyrus of freely moving rats is modulated by D1/D5 dopamine receptors

Hippocampal depotentiation comprises a reversal of tetanization-induced lon g term potentiation (LTP) which occurs following low-frequency stimulation. In the CA1 region, it has been reported that agonist activation of D1/D5 d opamine receptors enhances LTP expression and inhibits depotentiation. The role of these receptors in synaptic plasticity in the dentate gyrus (DG) ha s not been characterized. This study therefore investigated the role of D1/ D5 receptors in LTP and depotentiation in the DG of freely moving rats. Mal e Wistar rats underwent chronic implantation of a recording electrode in th e DG granule cell layer, a bipolar stimulating electrode in the medial perf orant path and a cannula in the ipsilateral cerebral ventricle (to enable d rug administration). The D1/D5 agonist Chloro PB dose-dependently inhibited depotentation in the DG. This effect was prevented by the D1/D5 antagonist SCH 23390. Neither D1/D5 agonist nor antagonist had an effect on LTP expre ssion or basal synaptic transmission. These results highlight differences b etween D1/D5 receptor-involvement in LTP and depotentiation in the CA1 regi on and DG, and indicate that whereas D1/D5 receptor activation may not he a critical factor in LTP induction in the DG, a differential role for these receptors in the expression of depotentiation, in this hippocampal subfield , may exist.