Binding sites of Drosophila melanogaster sex peptide pheromones

Drosophila melanogaster sex peptide (SP) and Ductus ejaculatorius peptide ( DUP99B) are male pheromones transferred in the seminal fluid to the female during copulation. Both reduce sexual receptivity and stimulate oviposition in females. The presence of high-affinity SP and DUP99B binding sites in t he female were investigated by incubation of cryostat tissue sections with I-125-iodinated peptides and subsequent autoradiography. We found that in a dult females radiolabeled SP and DUP99B bind to peripheral nerves, the sube sophageal ganglion, the cervical connective, to discrete parts of the thora cic ganglion, and to the genital tract. Weak and uniform labeling was detec ted in the neuropil of the brain and the thoracic ganglion. The labeling pa ttern in the nervous system suggests binding of the peptides to sensory aff erents or glial cells. Scatchard analysis of the binding of I-125-DUP99B to antennal nerves yielded a dissociation constant K-d of 6.4 nM. Competition experiments with peptide fragments show that the peptides bind with their homologous C-terminal regions. Binding sites in the nervous system of femal es are established throughout sexual maturation. Prominent binding of the p eptides to afferent nerves suggests modification of sensory input, (C) 2000 John Wiley & Sons, Inc.