CIRCADIAN RHYTHMS OF LOCOMOTOR ACTIVITY AND HIPPOCAMPAL CLOCK GENES EXPRESSION ARE MODIFIED IN VITAMIN A-DEFICIENT RATS

NAVIGATORE FONZO L; DELGADO, SM; GOLINI R; ANZULOVICH, AC

NUTRITION RESEARCH

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Storrs; Año: 2014 vol. 16 p. 118 - 121

0271-5317

The main external time-giver is the day-night cycle, however, feeding cycles and signals from the activity/rest cycle also can entrain peripheral clocks, such as the hippocampus, in the absence of light. Knowing that vitamin A and its derivatives, the retinoids, may act as regulators of the endogenous clock activity, the objective of the present study was to investigate the consequences of feeding rats, maintained under constant darkness conditions, with a vitamin A-free diet, on their locomotor activity rhythm as well as on the endogenous circadian patterns of clock genes and GSH levels, in the hippocampus. Locomotor activity was recorded during last week of treatment period. Circadian rhythms of clock genes expression were analyzed by RT-PCR in hippocampus samples isolated every 4 h during a 24h period. GSH levels were also determined by a kinetic assay. Regulatory regions of clock PER2, CRY1 and CRY2 genes were scanned for RXRE, RARE and RORE sites. As expected, rats´ locomotor activity pattern shifted rightward under constant darkness conditions. Clock genes expression and GSH levels display robust circadian oscillations in the rat hippocampus. We found RXRE and RORE sites on regulatory regions of clock genes. Vitamin A deficiency dampened rhythms of locomotor activity as well as modified endogenous rhythms of clock genes expression and GSH levels. Thus, vitamin A may have a role in the endogenous clock functioning and would participate in the circadian regulation of the cellular redox state in the hippocampus, a peripheral clock with a relevant function in memory and learning.