Pretectal influences on tectal response of the frog: Intracellular recording and field potentials analysis

Synaptic organization and spatiotemporal pattern of the tectal response to electrical stimulation of pretectal (Lpd/P) nuclei were examined in the bullfrog (Rana catesbeiana) by means of intracellular study and a current source density (CSD) analysis. The pretectal stimulation elicited mainly two types of responses (EI; I type) in the ipsilateral tectum, only one type of response (I type) in the contralateral tectum. EPSPs with short latencies were concluded to be monosynaptic. Most IPSPs were generated through di- or polysynaptic paths, but monosynaptic IPSPs were also recorded in both optic tecta. The antidromically invaded tecto-pretectal projecting cells were recorded in both tecta, which revealed reciprocal connections between the tectum and particular pretectal nuclei. In all CSD profiles, only one type of spatiotemporal pattern composed of one sink with short latency was observed. The short-latency sinks appear to be associated with monosynaptic activity generated by the pretectal inputs. The CSD analysis results show good accordance with the intracellular study.