ORGANIZATION OF CIRCADIAN RHYTHMICITY AND SUPRACHIASMATIC NUCLEI IN MALNOURISHED RATS

The present study was aimed at characterizing the effects of low-prote in malnutrition (6% casein) on the circadian rhythm of drinking behavi or and on suprachiasmatic nuclei immunohistochemistry in Sprague-Dawle y rats. Recordings were started at 30 days of age under a 12:12-h ligh t-dark (LD) cycle. At age 150 days, recordings were continued under co nstant dim red light, and finally the latency to entrain to complete a nd skeleton photoperiods was established. At the end of the recordings rats were processed for histological analysis. Compared with their co ntrols, malnournished rats exhibited 1) splitting of rhythmicity under LD that 2) condensed to one component in constant dim red light, 3) d elayed entrainment to skeleton photoperiod, and 4) precocious entrainm ent under complete photoperiod. Immunohistochemical analysis showed ma inly a decrease in the immunohistochemical detection of vasoactive int estinal polypeptide and glial fibrillar acid protein cells in malnouri shed animals. These results indicate that in malnourished rats there i s a decrease 1) in the coupling force among the oscillators and 2) in the strength of the phase lock between the oscillators and the light-d ark cycle.