Abstract
The weakly electric fish, Gnathonemus petersii, emits electric organ discharges (EOD) from the tail electric organ. In the electrosensory systems, variations in the discharge rate and amplitude of each 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 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.11 ms. In the presence of propofol or strychnine, EOD frequency decreased, but with a sharp tuning. The minimum latency for the EOD did not change. In the presence of Ketamine frequency tuning still remained, but the fixed latency became unclear. With the broad stimulation, the ratio of tuned EOD against untuned EOD was larger than that with local stimulation. The evidence suggests that GABAeargic pathways modulate the frequency tuning of EOD, while the glutamatergic neurons modulate the latency. [Jpn J Physiol 55 Suppl:S180 (2005)]
