The p65(AD)::CaM hemidriver contains the transcriptional activation domain from the Homo sapiens 'p65' gene (RELA, HGNC:9955) fused to calmodulin (CaM). It forms one half of a 'split driver' system that is designed to act as a transcriptional reporter of intracellular Ca[2+] (TRIC). The other half of the split system is a hemidriver containing a DNA-binding domain fused to a calmodulin target peptide. In the presence of Ca[2+], calmodulin binds to its target peptide, reconstituting a transcriptional activator that can drive expression of a downstream reporter or responder transgene. The DNA-binding specificity of the reconstituted transcriptional activator will depend upon the DNA-binding domain present in the DNA-binding domain-CaM target peptide hemidriver. The exact sequence of the p65(AD)::CaM hemidriver may differ depending on the particular transgene or modified endogenous locus being used. For example, the particular calmodulin sequence used may vary. The TRIC system may be particularly useful for monitoring and manipulating (via a downstream responder) neuronal responses that occur over long periods of time (FBrf0228535).