Apomorphine-induced suppression of prey oriented turning in toads is correlated with activity changes in pretectum and tectum: [14C]2DG studies and single cell recordings.

In common toads, after systemic administration of the dopamine agonist apomorphine (APO), prey-oriented turning was suppressed. Searching for neural correlates, the present study shows APO-induced increases in glucose utilization in the retinorecipient pretectum and dorsal optic tectum and a decrease in the medial tectal output layers. This pattern of metabolic activity is resembled by neuronal discharge activities recorded in response to a prey stimulus; the discharge rates are increased in retinal ganglion cells and pretectal neurons and decreased in tectal output neurons. We suggest that an APO-induced enhancement of pretecto-tectal inhibitory influences contributes to the reduction of tectal output, thus suppressing prey-oriented turning behavior.