A series of different antibodies against serotonin receptor 1A (5HT1A_R) have been reported although only limited information on the specificity of these antibodies and the antigens recognized is available.Herein, we characterized reactivity of an antibody by a gel-based proteomics method that should represent a model how antibodies may be defined in the future.An antibody against the 5HT1A_R was generated, used for immunoprecipitation and immunoblotting on blue-native gels containing a 5HT1A_R complex.The 5HT1A_R was isolated from tissue and was defined by nano-LC-ESI-MS/MS.