In the first of these comparisons, and normalized these values to the average peak amplitudes obtained from control GABAA expressing oocytes. Entries in columns 1 and 2 of Table 2 show the normalized peak amplitude of the GABA-elicited response for a given treatment. Entries in columns 3 and 4 indicate normalized peak amplitudes of the GABA-elicited response for each scFv after incubation with secondary antibody. This was done to study the effect on channel dynamics of adding a macromolecular, sterically bulky moiety to the scFv. The results indicate that the membrane current responses of oocytes incubated with and without the secondary antibody reagent are not substantially different. The second measure of comparison performed was to analyze the effects of a given treatment on the waveform of the GABA-elicited response. Determinations of L provide further information on the effect of scFv treatment. They show, specifically, that point-by-point comparison of peak-matched waveforms of untreated and treated oocytes yield goodness-of-fit values near unity, indicating high similarity in waveform kinetics, consistent with minimal or no effect on receptor channel activity upon treatment with scFvs. While physiological control of the receptor by a combinatorially-derived affinity reagent has been observed in previous studies, the absence of an effect of the scFvs studied here on the GABAA electrophysiological activity is consistent with the suitability of these scFvs as the anchor component of a prospective neuromodulator. In immunohistochemistry experiments on cryosections of mouse retina, we investigated the binding of A10, the a1-specific scFv described above. The results,U0126 shown in Figure 4A, indicate distinct staining of the ganglion cell and inner plexiform layers, consistent with previously reported data. A similar staining pattern was obtained with commercially available anti-a1 monoclonal antibody. The small differences in staining patterns obtained with the present scFv and the commercial antibody can be explained by possible differences in the epitopes used to generate the two antibodies. Further evidence that the staining by A10 is due to specific recognition of the receptor came from an experiment in which we tested an scFv raised against an unrelated target ]. This ZF130H1-directed scFv did not yield a layer-specific staining pattern in retina. These data demonstrate that the scFv A10 recognizes GABAA a1 subunit in the mouse retina. The present study demonstrates the successful isolation of scFvs against GABAA receptor subunits by phage display technology using synthetic peptides. These scFvs bind to their cognate peptide specifically, with minimal or no cross-reactivity to peptides of other GABA subunits. Significantly, these peptide-raised scFvs specifically bind intact GABAA receptors expressed in Xenopus oocytes, and appear not to substantially alter the receptor’s electrophysiological activity. Furthermore, A10, the a1-specific scFv,VE-822 labels mouse retina in layers expected to contain GABAA receptors. The results additionally show that dimerization of the A10 scFv yields a more robust reagent, as evidenced by the10-fold enhancement of sensitivity in dot blots and the more than 100-fold reduction in Kd value.