A mechanism underlying dopamine D1 and D2 receptor‐mediated inhibition of dopaminergic neurones in the ventral tegmental area in vitro

Dopamine (10 µM) and quinpirole (10-100 µM) hyperpolarized the membrane of type I dopaminergic neurones in the ventral tegmental area.

• Type I and type II neurones in the ventral tegmental area were classified based on action potential shape, indicating dopaminergic and non-dopaminergic categories.
• Quinpirole (10 µM) increased membrane conductance and inhibited both spontaneous and depolarization-induced action potentials in type I neurones.
• The effects of quinpirole were reversed by the D2 receptor antagonist domperidone (5 µM).
• Increased potassium concentration in the perfusing fluid or tetraethylammonium (10 µM) reduced the hyperpolarization induced by quinpirole.
• Simultaneous application of SKF 38393 (10 µM), a D1 receptor agonist, elevated the action potential threshold by 5-6 mV in the presence of quinpirole without enhancing hyperpolarization.
• Dopamine, quinpirole, and SKF 38393 had no effect on resting membrane potential or action potentials in type II neurones.

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