Aimed to reproduce the results of electrophysiological studies of synaptic signal transduction, conventional models of neurotransmission are based on the specific binding of neurotransmitters to ligand-gated receptor ion channels. However, the complex kinetic behavior observed in synaptic transmission cannot be reproduced in standard kinetic model without the ad hoc postulation of additional conformational channel states. On the other hand, if one invokes unspecific neurotransmitter adsorption to the bilayer—a process not considered in the standard models—the electrophysiological data can be rationalized with only the standard set of three conformational receptor states that also depend on this indirect coupling to neurotransmitters via their membrane interaction. Unlike for anesthetics, experimental verification has been difficult because of the low binding affinities of neurotransmitters to lipid bilayer. We quantify this interaction with surface plasmon resonance (SPR) spectroscopy to measure the equilibrium dissociation constant of neurotransmitter membrane association, as well as on and off rates under flow. Neutron reflectometry (NR) on artificial membranes is used to characterize structural aspects of the association of neurotransmitters with the membranes. Sparsely-tethered bilayer lipid membranes composed of zwitterionic (PC) and anionic (PS and PG) lipids were assembled and their interactions with serotonin, γ-aminobutyric acid (GABA), dopamine, and adenosine studied. SPR shows a wide range of binding affinities for different neurotransmitters. NR shows that the ligand with the largest affinity, serotonin, penetrates the membrane deeply whereas GABA associates with the bilayer peripherally. We establish that some neurotransmitters interact non-specifically with the lipid membrane matrix at physiologically relevant concentration and that this interaction differs vastly for different neurotransmitters.