THE EFFECTS OF A 3-DAY INCREASE OF AMBIENT-TEMPERATURE ON BODY-TEMPERATURE AND REM-SLEEP IN AN ANIMAL-MODEL OF DEPRESSION

This study examined the effects of elevated ambient temperature (Ta) o n body temperature (Tb) and rapid eye movement (REM) sleep in depresse d and control rats. Previous studies have shown that elevations of Ta to the rat's thermoneutral zone of 29 degrees C produced an increase o f REM sleep in control rats. In this study, 15 male Sprague-Dawley rat s, seven saline control rats (SAL) and eight rats that were classified as depressed according to the chlorimipramine model of depression (CL I rats), were implanted for continuous Tb and polysomnographic recordi ng and were exposed to two Ta's, 22 degrees C and 29 degrees C. CLI an d SAL rats had significantly more REM sleep and a lower body temperatu re at 29 degrees C than at 22 degrees C. At 22 degrees C, CLI rats had significantly more REM sleep during the light period and a higher Tb in the light and dark periods than SAL control rats. At 29 degrees C, there were no significant differences in REM sleep or in Tb between CL I and SAL rats. Because human endogenous depression is associated with abnormal REM sleep and an elevated nocturnal Tb, these results give f urther support for the validity of the CLI model of depression and pro vide insight into the relationships among Tb, Ta, REM sleep and depres sion.