INDEPENDENCE OF FEEDING-ASSOCIATED CIRCADIAN-RHYTHM FROM LIGHT CONDITIONS AND MEAL INTERVALS IN SCN LESIONED RATS

Free-running period of the feeding-associated circadian rhythm was ass essed in suprachiasmatic nucleus (SCN) lesioned rats under three diffe rent conditions using a feeding-fasting (FF) paradigm; restricted feed ing (RF) with meal intervals of 24 h (T=24 h) under 24 h light-dark cy cle (LD), RF with T=24 h under continuous dim light (dim LL), and RF w ith T=25 h under dim LL. After the termination of RF, the rats were su bjected to FF regimen five times repeatedly, in which food and water w ere available for 7 days, followed by total food deprivation for 3 day s with free-access to water. Free-running period, which was measured w ith reference to the prefeeding activity peak during food deprivation, was very close to 24 h and was not different under three conditions. It is concluded that the feeding-associated circadian rhythm has a maj or period close to 24 h, which is nor affected either by light conditi ons nor by meal intervals. (C) 1997 Elsevier Science Ireland Ltd.