The effects of neuroleptics with central dopamine and noradrenaline receptor blocking properties in the L-DOPA and (+)-amphetamine-induced waking EEG in the rat.

1 A study was carried out in rats (prepared for chronic sleep recording) of the effects of pretreatment with neuroleptics differing in their relative antinoradrenaline and antidopamine receptor potencies, on the L-DOPA and (+)-amphetamine-induced increase in waking EEG. 2 Haloperidol (0.6 mg/kg), which blocks central dopamine and noradrenaline (NA) receptors, reversed the EEG desynchronizing actions of L-DOPA and (+)-amphetamine. 3 Low doses of pimozide (0.4 to 0.8 mg/kg) which block dopamine receptors exclusively, were not able to modify the pharmacologically induced disruption of the sleep-awake cycle. However, at 1 mg/kg, a dose which also produces blockade of NA receptors, pimozide counteracted the increase in waking elicited by (+)-amphetamine. 4 Spiroperidol (1 to 4 mg/kg) which is devoided of NA receptor blocking properties, failed to reverse the L-DOPA or (+)-amphetamine-induced arousal. 5 Our results suggest that the increased waking time observed after the catecholamine agonists is related to an increased availability of NA rather than dopamine.