Electrophysiological evidences of mutual modulatory influences on the retinal activity of the crayfish Procambarus bouvieri (O).

Electroretinographic evoked potentials (ERGs) were recorded in dark adapted crayfish by the application of pulses of light (0.09 Cd/ft2) presented every 2.5 min. Heterolateral illumination (HI) for sixty min (0.06-0.3 Cd/ft2) induced up to 50% decrease in ERG after a latency of 12-25 min. ERG depression was proportional to the intensity of HI and also showed a circadian rhythm. During the alpha phase the ERG recovery started 3-10 min after HI was turned off. In contrast it started only after 10-20 min during the rho phase. The time course of the ERG depression, which was abolished in splitbrain animals, strongly suggests that a mutual modulatory influence, probably of neuroendocrine nature, is present in the crayfish visual system.