Influence of some dopaminoceptor agents on nitrazepam-induced sleep in the domestic fowl (Gallus domesticus) and rats.

The influence of apomorphine, levodopa and haloperidol was studied on nitrazepam sleep using young chicks and rats. In addition, the influence of dopamine and ADTN was studied in young chicks. Nitrazepam dose-dependently (0.4-51.2 mg/kg, i.p.) induced behavioural sleep in chicks. However, higher doses of nitrazepam (12.8-51.2 mg/kg, i.p.) were required to induce behavioural sleep in rats. Dopamine (12.5-100 mg/kg, i.p.) and ADTN (2.5-80 mg/kg, i.p.) delayed the onset but prolonged nitrazepam sleep in chicks: these effects were statistically significant. Levodopa (12.5-100 mg/kg, s.c.) and apomorphine (0.2-0.8 mg/kg, s.c.) profoundly delayed the onset and shortened the duration of nitrazepam sleep in both chicks and rats. Noradrenaline (20-80 mg/kg, i.p.) shortened the onset and prolonged nitrazepam sleep in chicks. Pimozide (1-8 mg/kg, i.p.) potentiated nitrazepam sleep and antagonized the effects of dopamine, levodopa and ADTN on nitrazepam sleep in chicks. Similarly, haloperidol (0.5-1.0 mg/kg, i.p.) potentiated nitrazepam sleep and antagonized the effects of levodopa and apomorphine on nitrazepam sleep in rats. The EEG synchronization and decreased EMG induced by nitrazepam (1.6 mg/kg, i.p., and 12.8 mg/kg, i.p., for chicks and rats, respectively) were antagonized by levodopa (12.5 mg/kg, s.c.). The behavioural and electroencephalographical results suggest that enhancement of dopaminergic neurotransmission may be involved in the mechanisms of wakefulness in both chicks and rats.