An eye-tectum preparation allowing routine whole-cell recordings of neuronal responses to visual stimuli in frog.

We propose an in vitro eye-tectum preparation enabling whole-cell recordings of tectal neurons combined with visual stimulation. The recordings were made from the tectum, which was cut in order to facilitate access to the cell bodies located in the inner tectal layers. The preparation remains viable for up to 5h while routine prolonged whole-cell recordings could be obtained from tectal neurons. Cutting of the tectum did not disrupt endogenous synaptic circuits and sensory inputs allowing examination of functional neuronal responses evoked with visual stimuli. Recordings from layer 6 tectal neurons indicated that neuronal responses were shaped by a mixture of excitation and inhibition generated by sensory input and local neuronal network. Visually evoked synaptic responses could also activate fast dendritic currents. Thus, the preparation brings about the benefits of in vivo recordings without the effects of anesthetics that could influence processing of sensory inputs. Using the proposed preparation, the network circuit function, which operates during central processing of a visual input, can be studied as well as the role of intrinsic properties of neurons in detection and processing of visual information.