Genetic advances in Drosophila provide for targeted expression of controllable molecules in genetically defined neurons, U0126 allowing regulated inhibition of neuronal activity. Approaches based on neuronal stimulation in Drosophila and other genetically tractable organisms have often been limited by a lack of efficient means for activating dispersed neurons in behaving animals. Photostimulation of genetically specified neural circuits using the directed expression of the ChR2 channel rhodopsin can be effectively used to regulate neuronal output. The stimulation of aminergic neurons in Drosophila larvae, for example, was previously shown to induce aversive and appetitive reinforcement. More recently, ChR2 was used to manipulate odorant neurons in adult flies. Using a series of overlapping synthetic peptides Dolimbek et al. successfully mapped continuous regions of BoNT/B recognized by antibodies derived from human, horse and mouse sera. Such experiments can identify immunodominant areas of a protein and they have often been used to identify antibody binding epitopes. However, this approach only detects linear epitopes and overlooks complex, conformational epitopes. Using phage display libraries expressing BoNT Hc gene fragments, the epitopes of two Hc-specific anti-BoNT antibodies were identified. Levy et al. reported the effective use of a randomly mutated BoNT/A heavy chain library, displayed on the surface of yeast cells, to identify single amino acids important in the epitopes of anti-BoNT/A monoclonal antibodies. In the absence of such libraries for the BoNT/A light chain, we have nonetheless been able to characterize the epitope of F1-40 to a similarly high resolution. We expect our experimental approach to increase the likelihood of identifying epitopes of other antibodies in the future, and to facilitate their characterization at the single amino acid level. Although the phage display analysis yielded the sequence QPDRS, it also provided the anomalous motif SSAFYPK in eight of the eleven sequenced plaques. Unlike the sequence QPDRS, this second sequence could not be mapped onto the light chain of BoNT/A, and it probably represents a mimotope of the F1-40 epitope. Mimotopes are commonly identified by phage display, and this faculty has been widely exploited to generate potential peptide vaccine candidates. When using phage display to search for an epitope, multiple mimotopes that bind a monoclonal antibody can be selected, and it is necessary to examine every mimotope to identify an epitope region. We demonstrate here that ChR2 stimulation offers temporal control of neural activity with millisecond precision over a wide range of frequencies, and can be used to manipulate both larval and adult behaviors. Such tight control of neural activity is a prerequisite if such photostimulation is to be used to mimic environmental stimuli, or for activation-based screens to identify the neural circuitry underlying innate behaviors.This keeps the serial interval the same.