DROSOPHILA NERVOUS-SYSTEM MUSCARINIC ACETYLCHOLINE-RECEPTOR - TRANSIENT FUNCTIONAL EXPRESSION AND LOCALIZATION BY IMMUNOCYTOCHEMISTRY

The pharmacological properties of a cloned Drosophila muscarinic acety lcholine receptor (mAChR) were investigated using two independent tran sient expression systems. The binding characteristics of the expressed receptor were determined using transfected COS-7 cells, whereas the m AChR functional properties were analyzed using nuclearly injected Xeno pus oocytes. Competition displacement studies with transfected COS-7 c ell membranes showed that N-[H-3]methylscopolamine binding was displac ed most effectively by atropine, followed by 4-diphenylacetoxy-N-methy lpiperidine methiodide, pirenzepine, and AFDX-116. This same order of effectiveness (4-diphenylacetoxy-N-methylpiperidine methiodide > piren zepine > AFDX-116) was observed in oocytes expressing Dm1 when carbamy lcholine-induced currents were inhibited by the same antagonists. Thus , the expressed Drosophila mAChR (Dml) exhibits a pharmacology that br oadly resembles that of the vertebrate M1 and M3 mAChR subtypes. To de termine the anatomical localization of the Drosophila mAChR, polyclona l antiserum was raised against a peptide corresponding to the predicte d carboxyl-terminal domain of the receptor. Immunocytochemistry on fly sections demonstrated that the mAChR gene product was found in the ne rvous system and was not seen in skeletal muscle. The most intense sta ining was localized to the glomeruli of the antennal lobes, an area of the insect brain where first-order synaptic processing of olfactory i nformation occurs.