The present invention relates to methods of identifying whether a candidate compound is a modulator of a G protein coupled receptor (GPCR). In certain embodiments, the GPCR is human. In certain embodiments, the GPCR is endogenously expressed by nerve cells or muscle cells. In certain embodiments, the GPCR is neuroprotective or myoprotective. In certain embodiments, the GPCR is a Humanin receptor. The invention also relates to methods of using said modulators of GPCRs. A preferred modulator is an agonist. The agonists of the present invention are generally used as therapeutic agents to prevent or treat neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, prions Associated diseases, stroke and motor neurone disease, especially peripheral neuropathy, cerebral amyloid beta-protein angiopathy and ischemic heart disease, including myocardial infarction and congestive heart failure.