MODEL OF P-ELECTRORECEPTORS AND T-ELECTRORECEPTORS OF WEAKLY ELECTRICFISH

To clarify the microscopic mechanisms by which P- and T-receptors enco de amplitude modulation and zero crossing time of jamming signals, we present a model of P- and T-receptors based on their physiological and anatomical properties. The model consists of a receptor cell, support ing cells, and an afferent nerve fiber. The basal membrane of the rece ptor cell includes voltage-sensitive Ca2+ channels, Ca2+-activated Kchannels, and leak channels of Na+, K+, and Cl-. The driving force of potential change under stimulation is generated by the voltage-sensiti ve Ca2+ channels, and the suppressing force of the change is generated by Ca2+-activated K+ channels. It has been shown that in T-receptor c ells the driving force is much stronger than the suppressing force, wh ereas in P-receptor cells the driving force is comparable with the sup pressing force. The differences in various kinds of response propertie s between P- and T-receptors have been consistently explained based on the difference in the relative strengths of the driving and suppressi ng forces between P- and T-receptor cells. The response properties con sidered are encoding function, probability of firing of afferent nerve , pattern of damped oscillation, shape of tuning curves, values of the optimum frequency, and response latency.