Phase Control of Ultradian Feeding Rhythms in the Common Vole ( Microtus arvalis): The Roles of Light and the Circadian System

Abstract

In their ultradian (2- to 3-hr) feeding rhythm, common voles show intraindividual synchrony from day to day, as well as interindividual synchrony between members of the population, even at remote distances. This study addresses the question of how resetting of the ultradian rhythm, a prerequisite for such synchronization, is achieved. Common voles were subjected to short light-dark cycles (1 hr darkness with light varying between 0.7 and 2.5 hr); to T cycles (long light-dark cycles in the circadian range—16 hr darkness and 3-13 hr light); to light pulses (15 min) during different circadian and ultradian phases; and to addition of D₂O to the drinking water (25%). Short light-dark cycles and D₂O were also applied to voles without circadian rhythmicity, after lesions of the suprachiasmatic nuclei.