THERMAL RESPONSES OF ACHROMATIC GANGLION-CELLS IN THE PHOTOSENSORY PINEAL ORGAN OF RAINBOW-TROUT ONCORHYNCHUS-MYKISS

1. The effect of ambient temperature (thermal response) on the neural activity in achromatic type of ganglion cells was studied in the dark-adapted pineal organ of the rainbow trout, Oncorhynchus mykiss. 2. The discharge rate of ganglion cells increased with increasing temperature. The thermal response could be classified into two types according to the temperatures showing the maximum discharge rate (20.73 +/- 1.7-degrees-C in type I, 29.12 +/- 1.4-degrees-C in type II). Above this temperature, the discharge rate decreased and the spikes partly disappeared. The spikes reappeared when the temperature was subsequently decreased. 3. These results suggest that the neural output of achromatic ganglion cells is modulated by the ambient temperature.