Effects of local activation and blockade of dopamine D4 receptors in the spiking activity of the reticular thalamic nucleus in normal and in ipsilateral dopamine-depleted rats

The reticular thalamic nucleus (RTn) controls the overall activity of thalamo-cortical neurons information processing. GABAergic RTn neurons have one of the highest densities of D4-type dopamine receptors in subcortical structures. The unitary electrical activity of RTn neurons was recorded in vivo in Wistar rats in order to study the effects of local activation and blockade of D4 receptors under both conditions, normal and ipsilateral lesion of the dopaminergic pathways. Our data suggest that: i) there is a tonic dopaminergic input to the RTn; ii) local activation of D4 receptors increases the basal firing rate of RTn neurons in normal and lesioned rats, and iii) local blockade of D4 receptors diminishes the firing rate in normal but not in lesioned rats. Altogether, our findings support that dopamine contributes to the spontaneous basal firing of the RTn neurons through D4-type dopamine receptors.