S-ANTIGEN ANTIBODY PARTIALLY BLOCKS ENTRAINMENT AND THE EFFECTS OF CONSTANT LIGHT ON THE CIRCADIAN-RHYTHM OF LOCOMOTOR-ACTIVITY IN THE ADULT BLOW FLY, CALLIPHORA-VICINA

Injection of S-antigen (arrestin) antibody into the brain of the blow fly, Calliphora vicina, appeared to reduce sensitivity to the photic e ffects of a light:dark cycle (LD; entrainment) or continuous ''bright' ' light (LL; arrhythmicity). In LD, a proportion of the injected flies evaded entrainment or showed delayed entrainment. In bright LL, flies continued with a free-running rhythm, which remained unchanged (as in continuous darkness) or lengthened (as in ''dim'' LL). These results focus attention on four groups of arrestin-positive neurons in the fly 's brain as potential components of the photoreceptive system.