DIURNAL BEHAVIORAL AND METABOLIC PATTERNS IN CHRONIC MALNOURISHED RATS

The temporal organization of behavioral patterns and metabolic activit y was assessed in chronic low protein malnourished rats and their nutr itional controls at 60 days of age. Spontaneous activity was video-rec orded during 3 days for 10 min every hour and the frequency of explora tion, grooming and ingestive behaviors was obtained, their basal metab olic rate was measured during 5 min every hour for one 24 h cycle. Rat s: of both nutritional groups showed a clear diurnal rhythmicity in al l behavioral patterns, characterized by an increase of activity during the dark phase and a decrease during the light phase. Effects of maln utrition were selective and produced mainly a general decrease of the mean value and amplitude of the rhythm of ingestive behavior, as well as a bimodal pattern and rhythmic components of 12, 24 and 30 h accord ing to autocorrelation and cosinor analysis. In both groups, the metab olic rate showed a bimodal diurnal rhythm, which fitted significantly to a 12 h period model and was not affected in malnourished rats. Thes e data provide evidence that the circadian system is highly resistant to malnutrition. In malnourished rats rhythmicity of ingestive behavio r was specifically affected, probably because the relation between met abolic processes and ingestive behaviors may be enhanced as a compensa tory mechanism aimed to counteract the deficient diet composition.