Circadian rhythms of locomotor activity and hippocampal clock genes expression are modified in vitamin A-deficient rats

NAVIGATORE FONZO L; GOLINI REBECA; DEYURKA NICOLAS; DELGADO, SM; ANZULOVICH, ANA CECILIA

Mendoza

Simposio; XII Latin American Symposium on Chronobiology; 2013

Signals from feeding and the activity/rest cycles can entrain peripheral clocks, such as the hippocampus, in the absence of light. Vitamin A might act as a regulator of the endogenous clock activity and modulate the cognitive function, through its retinoic acid receptors. Previously, we reported that RARα and RXRβ expression displays a circadian rhythm in the hippocampus, which is modified in the nutritional vitamin A deficiency (VAD). The objective of this study was to investigate the consequences of the nutritional VAD on the locomotor activity rhythm as well as on the circadian patterns of clock genes expression in the hippocampus of rats maintained under constant darkness (DD) conditions. Locomotor activity was recorded during the last week of treatment. Circadian rhythms of clock genes expression were analyzed by RT- PCR in hippocampus samples isolated every 4 h during a 24h period. Regulatory regions of clock Bmal1, Per2, Cry1/2 genes were scanned for RXRE and RARE sites. As expected, rats? locomotor activity pattern shifted rightward under DD conditions. Clock genes expression display robust circadian oscillations in the rat hippocampus. We found RXRE and RARE sites on regulatory regions of clock genes. VAD dampened rhythms of locomotor activity and modified endogenous rhythms of clock genes expression. The VAD affected the temporal patterns clock genes expression, probably by altering circadian rhythms of its own receptors.