Yawning induced by the selective dopamine D2 agonist N-0437 is blocked by the selective dopamine autoreceptor antagonist (+)-UH 232.

Yawning and stretching responses were elicited in rats by a small dose (0.3 mg/kg) of the highly selective dopamine D2 agonist, N-0437. The responses were blocked by the highly selective dopamine autoreceptor antagonist, (+)-UH 232 (3.0 mg/kg), but not by raclopride at a dose which selectively blocks postsynaptic D2 receptors. The results strongly confirm the view that yawning and stretching are behavioral responses elicited by stimulation of presynaptic D2 receptors.