Fos-like immunoreactivity in the circadian timing system of calorie-restricted rats fed at dawn: daily rhythms and light pulse-induced changes

Brain Res. 1997 Oct 3;770(1-2):228-36. doi: 10.1016/s0006-8993(97)00796-8.

Abstract

Daily rhythms of pineal melatonin, body temperature, and locomotor activity are synchronized to the light-dark cycle (LD) via a circadian clock located in the suprachiasmatic nuclei (SCN). A timed caloric restriction in rats fed at dawn induces phase-advances and further phase-stabilization of these rhythms, suggesting that the circadian clock can integrate conflicting daily photic and non-photic cues. The present study investigated the daily expression of Fos-like immunoreactivity (Fos-ir) and light pulse-induced Fos-ir in the SCN, the intergeniculate leaflet (IGL) and the paraventricular thalamic nucleus (PVT) in calorie-restricted rats fed 2 h after the onset of light and in controls fed ad libitum. A daily rhythm of Fos-ir in the SCN was confirmed in control rats, with a peak approximately 2 h after lights on. At this time point (i.e. just prior to the feeding time), the level of SCN Fos-ir was lowered in calorie-restricted rats. Concomitantly, IGL Fos-ir was higher in calorie-restricted vs. control rats. In response to a light pulse during darkness, Fos-ir induction was found to be specifically (i.e. phase-dependently) lowered in the SCN and IGL of calorie-restricted rats. Observed changes of Fos-ir in the PVT were possibly related to the wake state of the animals. This study shows that repetitive non-photic cues presented in addition to a LD cycle affect the Fos expression in the circadian timing system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies
  • Body Weight
  • Circadian Rhythm / physiology*
  • Darkness
  • Energy Intake*
  • Feeding Behavior*
  • Food Deprivation / physiology
  • Geniculate Bodies / physiology
  • Lighting
  • Paraventricular Hypothalamic Nucleus / physiology
  • Proto-Oncogene Proteins c-fos / analysis
  • Proto-Oncogene Proteins c-fos / immunology*
  • Rats
  • Rats, Wistar
  • Suprachiasmatic Nucleus / physiology

Substances

  • Antibodies
  • Proto-Oncogene Proteins c-fos