[en] 1-Azabicyclo[2.2.2]oct-3-yl α-(l-fluoropentan-5-yl)-α-hydroxy-α-phenylacetate (PQNPe) has been prepared and evaluated as a new candidate for the determination of muscarinic cholinergic receptor density by positron emission tomography (PET). The results of in vitro binding assays demonstrated that FONPe has high affinity for m_l and M₂ muscarinic receptor subtypes. Pretreatment of female Fisher rats with unlabeled FQNPe one hour prior to the intravenous administration of radioiodinated Z-(R,R)-IQNP, a high affinity muscarinic ligand, demonstrated FONPE significantly blocked the uptake of radioactivity in the brain and heart measured three hours post-injection of the radiolabeled ligand. These results demonstrate that this new fluoro analogue of QNB has high affinity for the muscarinic receptor and is able to effectively pass the blood-brain-barrier and localize in tissues rich in muscarinic receptors. The fluorine-18-labeled analogue thus represents an important target ligands for evaluation as potential receptor imaging agents in conjunction with PET. During this period several radioisotopes were provided to collaborators. Tungsten-188/rhenium-188 generators were provided as part of a CRADA project