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 scheduling of physiological activities. However, non-photic cues (e.g. environmental and social constraints) may also play a significant role. A natural model exists in the golden spiny mouse (Acomys russatus) which is nocturnal when maintained alone but diurnal when sharing a habitat with its congener, the common spiny mouse (A. cahirinus). We have recently observed that the presence of A. cahirinus provokes a major change in the daily rhythms of body temperature (Tb), and urine volume without affecting the melatonin rhythm and photoperiod-induced responses. The apparent lack of interaction between the daily and photoperiodic 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 resulted in diminution of urinary 6-sulfatoxymelatonin (6-SMT) and modification of Tb and urine volume rhythms. However, the modification of Tb and urine volume rhythms provoked by the presence of A. cahirinus were similar in pineal lesioned and sham-operated A. russatus. The non-photic signals released by A. cahirinus did not significantly affect glucose utilization in the suprachiasmatic nucleus of pineal- as well as sham-lesioned A. russatus. Thus, the modification of the daily scheduling of A. russatus by the photoperiod involves the pineal and/or the melatonin rhythm whereas non-photic cues effect a direct (perhaps masking), pineal-independent response to the competitor.