Seasonal modulation and non-24-hour entrainment of a circadian rhythm in a single neuron.

Abstract

The isolated abdominal ganglion of the sea hare (Aplysia californica) contains an identifiable neuron which has a circadian rhythm in the frequency of its autorhythmic spikes. It was found that: (1) the phase of the rhythm has a seasonal modulation such that during the cool season the maximum spike rate occurs near the time of projected dawn or dusk while during the warm season the maximum spike rate occurs near the time of projected midday or midnight; (2) the cellular rhythm can be entrained to environmental light cycles having periods of 21, 24, or 27 hr.; (3) 27-hr light cycles reduce the cell's mean level of activity. (15 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)