The electropinealogram, EPG, was recorded in response to light stimulation from the surface of the isolated pineal organ of five freshwater fishes. Dorsal recording of the pineal vesicle showed besically diphasic, first negative followed by positive, deflection when recorded with an AC amplifier. Recording from the ventral surface revealed reversed EPG. There was a tendency that the response amplitude of rainbow trout, ayu and catfish was larger than that of carp and goldfish. Response amplitude increased with dark adaptation and showed almost the maximum value within 30-40 minutes. Spectral sensitivity fit Dartnall's nomogram of V. P. 527nm in two fishes. Responses to flicker stimulus demonstrated very low CFF value ( ?? 1Hz) compared to that of the lateral eyes.
The present study revealed that the EPG would be a practical indicator for the comparative study of the pineal photosensoty function in fishes.
