Imaging CaLexA and TRIC Signals in the Dissected Fly Central Nervous System

Calcium-dependent nuclear import of LexA (CaLexA) and transcriptional reporter of intracellular calcium (TRIC) are transcription-based genetically encoded calcium indicators (transcriptional GECIs). When expressed in neurons, CaLexA and TRIC report neuronal activity by converting intracellular calcium levels into transcription activities and, subsequently, reporter gene expression. CaLexA and TRIC have been used successfully in many studies to label neurons associated with particular behaviors, regulated by internal states, or evoked by specific sensory inputs. This protocol details procedures for generating flies expressing genetic components of CaLexA and TRIC in specific neurons, performing immunostaining to label CaLexA and TRIC signals, and quantifying the signals using an open-source imaging analysis software.