Chronic Ethanol Intake Alters Circadian Period‐Responses to Brief Light Pulses in Rats

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Abstract
Although chronic alcohol intake is associated with widespread disruptions of sleep‐wake cycles and other daily biological rhythms in both human alcoholics and experimental animals, the extent to which the chronobiological effects of alcohol are mediated by effects on the underlying circadian pacemaker remains unknown. Nevertheless, recent studies indicate that both adult and perinatal ethanol treatments may alter the free‐running period and photic responsiveness of the circadian pacemaker. The present experiment was designed to further characterize the effects of chronic ethanol intake on the response of the rat circadian pacemaker to brief light pulses. Ethanol‐treated and control animals were exposed to 15‐min light pulses during either early or late subjective night on the first day of constant darkness following entrainment to a 12:12 light‐dark cycle. Relative to pulses delivered during early subjective night and to “no‐pulse” conditions, light pulses delivered during late subjective night resulted i...