Pimozide blocks the open-field hyperactivity produced by lesions of the ventral noradrenergic bundle in rats.

Selective, bilateral, radiofrequency destruction of the ventral noradrenergic bundle resulted in a substantial fall in hypothalamic but not cortical levels of noradrenaline. Ventral bundle-lesioned rats displayed, as compared to sham-operated animals, a pronounced enhancement of ambulation in both peripheral and central squares together with a reduction in immobility and an enhancement of rearing upon introduction into a novel open-field space. Grooming behaviour was not, in contrast, significantly modified. Pretreatment with the dopamine receptor antagonist, pimozide, strongly decreased this hyperactivity without significantly altering the behaviour of sham animals. These data suggest that the ventral bundle plays a role in the control of open-field locomotor behaviour and that this action may be exerted via an interaction with a dopaminergic network.