*Corresponding author e-mail: kmgouveia@ufrnet.br Introduction: A wide variety of behavioural and physiological processes display circadian rhythms which are generated by a time-keeping system, called circadian timing system. Two principal brain centers compose this system in mammals: a known central pacemaker, the hypothalamic suprachiasmatic nucleus (SCN), and a secondary component, the thalamic intergeniculate leaflet (IGL). The lipids are essential components to maintain the body metabolic balance. In addition, we know that polyunsatured fatty acids (PUFA) are essential for the development of the central nervous system and its lack in the diet, especially omega-3 and omega-6, important components of cellular membrane, allows changes in structure and functioning of the brain. The aim of this work was to evaluate the effects of a PUFA deficient diet on the expression of the circadian rhythms in rats Wistar. Methods: A group of animals was submitted to a PUFA lacking diet since gestational period until adulthood (experimental group) and another group to a normal diet (control group). Both groups were first exposed to a LD 12h-light (150 Lux)-12h-dark (1 Lux) cycle. After 2 weeks in this regimen, the time of lights-on was delayed by 6 hours; 3 weeks later, it was advanced by 6 hours, and 4 weeks later, the animal were placed in constant dark conditions. After 4 weeks the animals were then returned to LD 12:12 for 3 more weeks and then again to constant darkness for 4 weeks. The locomotor activity of the animals was measured using an infrared motion sensor above the cage. Output from the sensors was integrated with an computer running data acquisition software. Analysis of thythm characteristics and graphical output, actograms, were undertaken using the El Temps computer program (Diez-Noguera, Barcelon, Spain). ] Results: The analysis of the actograms shows that the experimental animals spend more time to attain the synchronization (mean 10,3 cycles) compared to control group animals (mean 5,3 cycles). Conclusion: These results allow us to conclude that a PUFA lacking diet affects the circadian rhythms regulation. Support: CNPq, CAPES, FINER FAPEAL-AL, PROPESQ- UFRN. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil
Gouveia et al. (Thu,) studied this question.