FMRFamide tagging--how an ionotropic receptor can be used to measure peptide secretion. Journal   Methods (San Diego, Calif.) Citation   Methods. 33(4):295-301 Publication date   2004 Aug Authors   Whim MD Moss GW Investigators   Matthew Whim Grant agencies   National Institute of Neurological Disorders and Stroke Grants   NINDS NS04754301 Abstract   In this chapter, we describe a technique, FMRFamide tagging, that in principle can be used to measure the release of any sequenced neuropeptide. The method relies upon the addition of an "electrophysiologically active" tag to the prohormone that encodes the neuropeptide of interest. Secretion of the electrophysiological tag (and thus the peptide of interest) is detected by activation of the ionotropic "tag receptor." Both the tagged prohormone and the tag receptor are expressed in the cell type under investigation. Since the tag and the neuropeptide of interest are on the same prohormone they are co-secreted and thus secretion of the tag reflects the co-secretion of the neuropeptide of interest. This method can be used to detect neuropeptide secretion on a millisecond timescale.