ラット網膜電図の概日リズム及び制御機構

Circadian rhythm in the electroretinogram (ERG) in continuous darkness (DD) over a long period were examined to find whether a free-running rhythm in retinal function exists in rats and if the rhythm is related to the circadian control system in the suprachiasmatic nucleus (SCN) in SCN lesioned rats. ERGs were recorded every 4 hours over 48 hours under a 12-hour light/dark cycle (LD) in SCN non-lesioned or lesioned rats, and on days 61, 85, 97 and 117 in DD in SCN non-lesioned rats. Locomotor activities were examined concurrently to compare the rhythms in the ERG. The amplitudes of the a- and b-waves changed in a circadian fashion in both LD and DD in the SCN non-lesioned rats. The acrophases shifted for every measurement in DD. The mean free-running period in the ERG and locomotor activity rhythms were 24.50 hours. However, no circadian rhythm was observed in the ERG or locomotor activity in the SCN lesioned rats. These results indicated that a circadian rhythm exists in the rat retinal function, in which the rhythm free-runs with the same periodicity as that for locomotor activity, and a circadian rhythm for retinal function was confirmed to be associated with the SCN.