Dopamine modulates the responsivity of mediodorsal thalamic cells recordedin vitro

The mediodorsal thalamic nucleus (MD) receives convergent inputs from subco rtical limbic structures that overlap with a dopaminergic (DA) innervation. In this study, we describe the effects of DA agonists on the basal and evo ked electrophysiological activity of identified thalamic cells of rats reco rded in vitro. Administration of the DI agonist SFK 38393 (10 mu M) did not produce a clear effect on the physiological properties of the thalamic cel ls recorded. In contrast, bath administration of the D2 agonist quinpirole (10 mu M) resulted in an enhancement of membrane excitability, facilitation of the occurrence of low-threshold spikes (LTSs), and changes in the resti ng membrane potential of the thalamic cells tested. The quinpirole-mediated responses were reversed by administration of the D2 antagonist haloperidol . Results from experiments performed with different [K+] and K+ channel blo ckers suggest that the effects of quinpirole are mediated at least in part by changes in K+ conductances. The results from this study suggest that DA can modulate the excitabitity of thalamic cells and in turn may influence t he way that the thalamocortical system integrates information.