Action of deuterium oxide upon the ERG circadian rhythm in crayfish, Procambarus bouvieri

Abstract

1. 1. We studied the action of deuterium oxide upon the rhythm of the ERG's amplitude recorded in intact animals and in isolated eyestalks. 2. In the isolated eyestalks the circadian rhythm of the ERG prevails. However, this rhythm differs in some features of the intact animal. The most prominent difference consists of the appearance of high frequency (ultradian) cycles superimposed on the circadian oscillation. 3. The deuterium oxide effect upon the circadian rhythm of the ERG, both in the intact animal, as well as in the isolated eyestalk, consists of (a) a decrease of the ERG's amplitude; (b) decrease in the amplitude of the oscillation; (c) alteration of the α: ρ ratio; and (d) lengthening of the period. The lengthening of the ultradian and circadian periods is proportional to the deuterium oxide doses applied. 4. Deuterium oxide has a greater effect upon the isolated eyestalk than upon the intact animal. 5. Deuterium oxide does not affect the number of high frequency cycles in the isolated eyestalk; it only increases their duration and probably enhances the cohesion of the corresponding oscillators. 6. We suggest that the lengthening of the circadian period produced by deuterium oxide is due to its action upon the high frequency oscillators. This action, in turn, could be due to the dissolving characteristics or higher molecular weight of the deuterium oxide.