Forebrain-mediated control of visually guided prey-catching in toads: investigation of striato-pretectal connections with intracellular recording/labeling methods.

ABSTRACT

Studies in anurans have shown that ablation of the whole telencephalon (or the caudal striatum) abolishes visual prey-catching behavior, whereas an additional lesion to the pretectum leads to hyperexcited, "disinhibited" prey-catching. This suggests a disinhibitory gating/arousal function mediated by two inhibitory projections telencephalon to pretectum and pretectum to tectum. Since the latter projection has been physiologically investigated already in great detail, the present paper focuses on the former projection. Intracellular recordings from the pretectal region in response to electrical stimulation of the ipsilateralcaudal ventral striatum or the ipsilateral lateral forebrain bundle revealed cells that display pure inhibitory postsynaptic potentials with short latencies of 2-3 ms, indicative for monosynaptic striato-pretectal connection. But it must be emphasized that a relatively large number of pretectal neurons of this sample showed sequential excitatory/inhibitory postsynaptic potentials. The latter data are not in conflict, with the hypothesis, rather they open new perspectives for further investigations.