Disk-shedding in the rat retina: lithium dampens the circadian rhythm but potentiates the light response.

Disk-shedding in the rat retina undergoes a circadian rhythm. Chronic lithium treatment significantly dampens the rhythm in constant darkness, but does not alter the timing or amplitude of the peak in a light-dark cycle. Lithium potentiates light-elicited disk-shedding with a maximal effect at the end of the subjective light phase, when light alone evokes only a moderate response. Although serum lithium levels show a diurnal variation, retinal lithium concentration remains high throughout 24 h. Thus lithium induces alterations in retinal rhythms as well as in photoreceptor metabolism.