Keywords: Glucagon-like peptide-1 receptor; Electrophysiology; Channelrhodopsin; Preproglucagon; GLP-1; PPGAP, area postrema; BNST, bed nucleus stria terminalis; DMH, dorsomedial nucleus of the hypothalamus; DMV, dorsal motor nucleus of the vagus; Ex-4, Exendin-4;