Behavioural effects of GABA-agonists and antagonists infused in the mesencephalic reticular formation - deep layers of superior colliculus.

Unilateral infusion of GABA-receptor antagonists (picrotoxin, bicuculline) in the mesencephalic reticular formation-deep layers of the superior colliculus (MRF-DLSC) elicits tight head-to-tail contralateral posturing but not active circling. Bilateral infusion of the GABA antagonists in the MRF-DLSC elicits compulsive gnawing and biting but not licking or sniffing. Infusion of GABA-receptor agonists (muscimol, THIP) in the MRF-DLSC while producing only minor or no motor or behavioural effects, drastically altered apomorphine effects; thus, unilateral infusion of muscimol resulted i tight, head-to-tail ipsiversive circling while bilateral infusion of muscimol converted the apomorphine-syndrome from stereotypy of high-intensity into pure compulsive forward locomotion devoid of sniffing. The results indicate that GABAergic mechanisms in the MRF-DLSC are of primary importance in the expression of motor and behavioural syndromes arising from the striatum.