Dopamine depresses polysynaptic inhibition in rat subicular neurons

Schizophrenia is considered to be associated with a hyperfunction of the do paminergic system and with abnormalities in hippocampal information process ing. To clarify whether an enhanced dopaminergic activity alters the hippoc ampal output, the effect of dopamine (DA) on inhibitory postsynaptic respon ses (IPSPs) in subicular neurons was examined. DA (200 mu M) induced a smal l and inconsistent hyperpolarization that was accompanied by a reduction of membrane resistance. DA decreased polysynaptic IPSPs which was paralleled by a depression of isolated AMPA/kainate and NMDA receptor-mediated excitat ory postsynaptic responses (EPSPs). In contrast, DA had no effect on isolat ed monosynaptic GABA(A) and GABA(B) receptor-mediated IPSP/Cs. We conclude that in addition to membrane effects, DA decreases polysynaptic IPSPs by at tenuating the glutamatergic drive onto subicular interneurons. (C) 2000 Els evier Science B.V. All rights reserved.