THE IMPACT OF BETA-ADRENERGIC-BLOCKADE ON DAILY RHYTHMS OF MELATONIN AND BODY-TEMPERATURE OF GOLDEN SPINY MICE ACOMYS RUSSATUS

beta-adrenergic stimulations induces melatonin synthesis and non-shive ring thermogenesis (NST) in rodents. The golden spiny mouse, Acomys ru ssatus is a nocturnal species capable of diurnal activity when coexist ing with its congenitor the common spiny mouse A. cahirinus. We have i nvestigated the impact of beta-adrenergic blockade on 6-sulphatoxymela tonin (6-SMT -a metabolite and index of melatonin production) and body temperature (T-b) daily rhythms in male A. russatus. Mice were acclim ated to an ambient temperature (T-a) of 28 degrees C, under two photop eriod regimes (16L:8D; 8L:16D). The daily rhythms of T-b and urinary 6 -SMT were measured for a period of 30 h at intervals of 4 h. Propranol ol (4.5 mg/kg, i.p.) was administered one hour before lights went off (i.e. when beta blockade does not affect NST in this species) and both variables were measured for another 30 h. The beta blocker markedly a ugmented melatonin output of A. russatus under both photoperiod regime s. The elevation in melatonin secretion was accompanied with an increa se in T-b of only 16L:8D-acclimated mice (i.e. shorten duration of mel atonin peak). However, in 8L:16D-acclimated mice, a phase advance of a bout 4 h was noted in 6-SMT daily rhythm. These results indicated that the role of sympathetic innervation in regulation of melatonin synthe sis in A. russatus differs from that in the rat. In addition, these da ta are compatible with the hyperthermic action of melatonin in this sp ecies. Therefore, it is suggested that in A. russatus, other neural pa thways are involved in its pineal regulation.