Suprachiasmatic nuclei lesions in the rat: alterations in sleep circadian rhythms.

After continuous control recording (24 h/day) during 5 days, 14 rats received sham, complete or incomplete lesions of the suprachiasmatic nuclei (SCN). Sleep records were analysed from the 22nd to the 27th day after the lesion. In rats with complete lesions of the SCN, there was a strong decrease in the amplitude of the circadian variation in slow wave (SWS) and paradoxical (PS) sleep. The acrophase of SWS remained unaltered whereas that of PS shifted towards the end of the illumination (7.00--19.00 h) period. The importance of these changes in sleep organization seems to be correlated with the size of the SCN lesion.