Apomorphine-induced modulation of neural activities in the ventrolateral striatum of rat

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The dopaminergic system in the ventrolateral portion of striatum(Svl), a part of basal ganglia, plays an important role in the regulation of orofacial movements : bilateral co-stimulation of both dopamine D1-like and D2-like receptors elicits repetitive jaw movements in rats. However, it is still unknown how activities of Svl neurons are modulated by activation of dopaminergic receptors. In the present study, we systematically injected apomorphine(2 mg/kg i. v.), a non-selective dopamine receptor agonist, that induced jaw movements under urethane anesthesia, and performed multi-channel unit recording from Svl neurons. According to the spike firing patterns, the Svl neurons were classified into two subtypes ; phasically active(PA) and tonically active(TA) neurons. The divergent effects of apomorphine on PA neurons in the Svl might reflect differential expression of D1-like and D2-like receptors in the middle spiny neurons. Apomorphine-induced suppression of TA neuron activities with decreased synchronized outputs is likely to reduce locally released acetylcholine, which may modulate apomorphine-induced jaw movements.