Suprathreshold excitation of network of frog tectal neurons by discharging of single retina moving-edge detector

Antanas Kuras, Armantas Baginskas, Vaida Batulevičienė

Institute for Biomedical Research, Kaunas University of Medicine, Lithuania

Key words: retinotectal transmission, neuronal network, suprathreshold excitation, frog retina, moving-edge detector, darkness detector.

Summary. Objective. It has been shown that discharge of single darkness detector in the frog retina can lead to suprathreshold excitation of the tectal neurons. The present study was designed to explore whether a suprathreshold excitation of frog tectal neurons can be elicited by the discharge of single moving-edge detector.

Material and methods. The discharge of a single retina ganglion cell was elicited by the electrical stimulation. The evoked electrical activity of the tectal neurons was recorded by the carbon-fiber microelectrode brought into the optic fiber layer F.

Results. The obtained data have suggested that a discharge of a single retinal moving-edge detector elicits a suprathreshold excitation of tectal neurons. The suprathreshold excitation of the tectal neurons is achieved due to the frequency facilitation of the fast retinotectal synaptic potentials.

Conclusions. Results of the present study suggest that activation of moving-edge detector gives rise to the same effects as the activation of the darkness one. However, the stronger excitation (the longer volleys of action potentials) for the moving-edge detector is needed to evoke suprathreshold excitation of tectal neurons compared to the darkness one. This difference could be caused by a lower quantal size of neurotransmitter release in synapses of the retinotectal input from the moving-edge detector than from the darkness one.

Correspondence to A. Kuras, Institute for Biomedical Research, Kaunas University of Medicine, Eivenių 4, 50009 Kaunas, Lithuania. E-mail: kuras@trc.kmu.lt

Received 17 August 2005, accepted 20 September 2005