In extensive work over the last decade, it has become clear that biologically? active molecules can be inserted into specific cell types through targeting to molecules on the cell surface. It is here proposed to direct this technology to specific neuronal cell types with the purpose of temporarily inhibiting their capacity of releasing neurotransmitters. As proof of concept, it is proposed to synthesize a conjugate of the neuropeptide substance P and the enzymatic (light) chain of botulinum toxin from C. botulinum strain E (BTELC) and examine the effects on cells that express both the substance P receptor and SNAP-25, the substrate for the enzymatic activity of BTELC. SNAP-25 is an essential player in neurotransmitter release, and its cleavage by BTELC would prevent release. Entry into a specific cell type would be provided by the substance P moiety, since only binding to its receptor would cause internalization. The process requires the cloning and expression of BTELC and the synthesis of a? substance P analog that would allow conjugation.? ? Inhibition of neurotransmitter release would be a short-term phenomenon, because slowly over time SNAP-25 would be re-synthesized and re-occupy its original position in the SNARE complex that is necessary for release. This would be an approximately one-month process.? ? The demonstration of efficacy would usher in a new technology with applications as research reagents. Targeted BTELC could be used to shut down neuronal subtypes, allowing observation of the effect and greater understanding of the function of the cell in systems biology, while the return to homeostasis and function would act as a? control for the experiment. Therapeutic applications for the treatment of neuropsychiatric and other maladies could result from this technology, but are not the focus of this application.