In 3 experiments with 200 Sprague-Dawley and Long-Evans rats, it was found that following blinding there was a rapid and sustained increase in eating and drinking during the light portion of a light-dark (L-D) cycle. Group nocturnal rhythms in eating and drinking were retained in attenuated form for at least 10 days; 60 days after blinding these rhythms were absent. For sighted Ss the food/water ratio was 3 times greater during the light than during the dark; this difference was greatly reduced almost immediately after blinding. Continuous illumination almost immediately suppressed water intake and abolished group nocturnal rhythms in eating and drinking within 9-11 days. Nocturnal eating and drinking rhythms reentrained within 7-9 days following an inversion of the L-D cycle. Ss blinded between 12 and 36 hr. after such an inversion remained residually entrained to the original L-D cycle for at least 1 mo., but Ss blinded at 48-120 hr. reentrained to the new cycle. These differences persisted for surprisingly long times and suggest that the initial period following a change in environmental illumination is most critical for reentrainment of eating and drinking which may then proceed relatively normally in the absence of further visual stimulation. Nocturnal patterns of drinking were present in essentially adult form in Ss 23 days old; blinding on Day 14 but not on Day 18 or later prevented the appearance of these rhythms. The early perinatal period was not critical for entrainment of eating and drinking rhythms since Ss 1st exposed to alternating L-D patterns of illumination at 59 days of age displayed nocturnal behavior patterns shortly thereafter. The influence of daytime feeding schedules on nocturnal drinking patterns is described and the neural basis for rhythmic light-dependent behavior considered.
Zucker, I.: Light-dark rhythms in rat eating and drinking behavior
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