In rats with cannulae permanently implanted into the third cerebral ventricle, the effects of different pharmacological manipulations affecting dopaminergic mechanisms, were studied on behaviour and electrocorticographic (ECoG) activity, continuously quantified in its spectrum power. The intraventricular injection (0.1-1 nmol) of (-)3PPP[3-(3-hydroxyphenyl) N-n-propylpiperidine], a specific agonist at dopamine (DA) autoreceptors, produced dose-dependent behavioural sedation or sleep and an increase in ECoG spectrum power, with a predominant increase in the lower frequency bands. Short episodes of stereotyped movements, wet-dog syndrome, penile grooming and erection were also observed. Similar behavioural and ECoG effects were elicited by the intraventricular injection of R-(+)-8-chloro-2,3,4,5-tetrohydro-3-methyl-5-phenyl-1H-3-benzazepi ne-7-ol (SCH 23390), a selective antagonist at D1 postsynaptic receptors, although these were preceded by a short period of behavioural and sexual stimulation. In addition, the intraventricular administration of some neuroleptics, chloropromazine and haloperidol, produced behavioural and ECoG slow wave sleep. No significant changes were observed with a neuroleptic drug, 1-sulpiride, which is reputed to act selectively as an antagonist at dopamine D2 receptors. In conclusion, the present experiments add new evidence in favour of the idea that dopaminergic mechanisms are involved in mammalian species in the control of arousal and that both post-synaptic D1 and D2 receptors may take part in such a control.