A bilayer lipid membrane sensor comprises (1) a gold recording surface; (2) a 1st lipid layer which is an imperfect layer of a thiolipid comprising the 2 phospholipid mols. linked to each end of a disulfide group, each through an oxyethylene chain short enough to allow the thiolipid to become anchored to the gold surface by self-assembly, but long enough to trap an aq. layer between the gold surface and the bottom of the thiolipid layer, the thiolipid being attached to the gold surface and the imperfect layer being completed by a phospholipid which provides an unattached fluid phase at room temp.; and (3) a 2nd lipid layer of phospholipid. The sensor is esp. useful for measuring changes in elec. resistance and/or capacity when it is prepd. to contain a receptor protein and an analyte contg. an agonist to the receptor is contacted with the bilayer. Thus, bis[8-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)-3,6-dioxaoctyl]disulfide monohydrate was prepd.; attached to a gold electrode; coated with an imperfect layer of DPPC, DMPC, or POPC; and incorporated with 5-HT3 receptor derived from calf brain as sensor for measuring the influence of serotoninergic agonists and antagonists (e.g. 5-hydroxytryptamine, 1-phenylbiguanide, and ICS 205-930). [on SciFinder (R)]