Fos-like immunoreactivity in the circadian timing system of calorie-restricted rats fed at dawn: daily rhythms and light pulse-induced changes.
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.
Challet
E
E
Neurobiologie des Fonctions Rythmiques et Saisonnières, CNRS URA1332, Strasbourg, France. e-challet@nwu.edu
Jacob
N
N
Vuillez
P
P
Pévet
P
P
Malan
A
A
D000818:Animals; D000906:Antibodies; D001835:Body Weight; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D002149:Energy Intake; D005247:Feeding Behavior; D005508:Food Deprivation / Q000502:physiology; D005829:Geniculate Bodies / Q000502:physiology; D008029:Lighting; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000276:immunology*; D051381:Rats; D017208:Rats, Wistar; D013493:Suprachiasmatic Nucleus / Q000502:physiology
D000906:Antibodies; D016760:Proto-Oncogene Proteins c-fos