Antagonism of pentobarbitone sleep by dopamine, levodopa and apomorphine in chicks.

1. The influence of dopamine, levodopa and apomorphine on sleep produced by pentobarbitone was studied in 1-14 day old chicks. 2. Pentobarbitone-induced sleep was associated with synchronization of the electroencephalogram (EEG) of the hyperstriatum, optic tectum and pontine reticular formation. 3. Dopamine desynchronized the EEG and antagonized pentobarbitone-induced EEG synchronization. 4. High doses of dopamine produced a delayed sleep which was potentiated by pimozide and antagonized by adrenoreceptor blocking agents. 5. Dopamine, levodopa and apomorphine delayed the onset and shortened the duration of pentobarbitone-induced sleep; apomorphine was the most potent. 6. Pimozide prolonged the duration of pentobarbitone-induced sleep, but had less effect when dopamine was also given.