THE PERIOD CLOCK GENE IS EXPRESSED IN CENTRAL-NERVOUS-SYSTEM NEURONS WHICH ALSO PRODUCE A NEUROPEPTIDE THAT REVEALS THE PROJECTIONS OF CIRCADIAN PACEMAKER CELLS WITHIN THE BRAIN OF DROSOPHILA-MELANOGASTER

The period protein (PER) is an essential component of the circadian cl ock in Drosophila melanogaster. Although PER-containing pacemaker cell s have been previously identified in the brain, the neuronal network t hat comprises the circadian clock remained unknown. Here it is shown t hat some PER neurons are also immunostained with an antiserum against the crustacean pigment-dispersing hormone (PDH). This antiserum reveal s the entire arborization pattern of these pacemaker cells. The arbori zations of these neurons are appropriate for modulation of the activit y of many neurons and they might interact with PER-containing glial ce lls. A putative physiological role of PDH in the circadian system is d iscussed.