Effects of dopamine on interaction of the two corticostriatal systems in rat somatosensory striatum

The intracellular responses of single striatal neurones under Chloralose and Urethane (1% & 10%; 10ml/Kg, i.p.) anaesthesia to stimulation of the contralateral barrel cortex and whisker pad were studied in normal rats and in rats with unilateral 6-hydroxydopamine lesion of midbrain dopaminergic neurones. In normal rats both stimuli depolarise striatal cells and EPSPs in response to whisker pad stimulation have a rapid rise time, while the contralateral cortically derived EPSPs are slower to rise and the spike initiation latency more variable. The two pathways also interact at the level of a single striatal cell. In dopamine depleted animals both stimuli were also able to depolarise the spiny neurones to their firing threshold. However the EPSPs to whisker pad stimulation were significantly slower to rise compared to control animals and were similar to cortically derived EPSPs. The interaction of the two pathways was also affected by the loss of dopamine.