抄録
The weakly electric fish, Gnathonemus petersii, generates a biphasic electric field from it's own pulse-type electric organ discharges (EOD) in the electric organ located at the base of tail. In the electrosensory systems, variations in the discharge rate and amplitude of own EOD enable the fish to detect local distortions of the electric field as 'electrolocation', and broad distortions evoked by other fish as 'electrocommunication'. In the present work, we examined how sensory stimuli changed the frequency of EOD in electrolocation and communication. In the behavioral experiments, each fish had it's own specific frequency, which was discharged during free swimming. When a metal rod was placed near the side of the fish, the frequency of EOD transiently increased from 5-10 Hz to c.20 Hz, while with the broad stimuli applied between the head and tail, the fish responded with a interval of EOD tuned to the stimulus frequency, with a minimum latency of c.10 ms. In the presence of propofol, that was activator of GABA-A receptor, EOD frequency decreased, but with a sharp tuning. The minimum latency of EOD for stimulus did not change. With a local injection of d-TC near the electric organ, neither responded to EOD frequency tuning nor fixed latency. This evidence suggests that sensory inputs are necessary for frequency tuning of EOD, and that the inhibitory GABAeargic neurons modulate the EOD frequency. [Jpn J Physiol 54 Suppl:S187 (2004)]
