INVOLVEMENT OF THE PINEAL-GLAND IN DAILY SCHEDULING OF THE GOLDEN SPINY MOUSE

The light-dark cycle is the major time cue for daily and seasonal sche duling of physiological activities. However, non-photic cues (e.g. env ironmental and social constraints) may also play a significant role. A natural model exists in the golden spiny mouse (Acomys russatus) whic h is nocturnal when maintained alone but diurnal when sharing a habita t with its congener, the common spiny mouse (A. cahirinus). We have re cently observed that the presence of A. cahirinus provokes a major cha nge in the daily rhythms of body temperature (T-b), and urine volume w ithout affecting the melatonin rhythm and photoperiod-induced response s. The apparent lack of interaction between the daily and photoperiodi c scheduling was further investigated by studying the significance of the pineal to the modification of A. russatus daily rhythms induced by the presence of A. cahirinus. Lesion of A. russatus pineal gland resu lted in diminution of urinary 6-sulfatoxymelatonin (6-SMT) and modific ation of T-b and urine volume rhythms. However, the modification of T- b and urine volume rhythms provoked by the presence of A. cahirinus we re similar in pineal lesioned and sham-operated A. russatus. The nonph otic signals released by A. cahirimus did not significantly affect glu cose utilization in the suprachiasmatic nucleus of pineal- as well as sham-lesioned A. russatus. Thus, the modification of the daily schedul ing of A. russatus by the photoperiod involves the pineal and/or the m elatonin rhythm whereas non-photic cues effect a direct (perhaps maski ng), pineal-independent response to the competitor.