The ECR2-TAC1prom transgene can be activated by cell depolarisation. A, Diagramatic representation (not to scale) demonstrating the linear relationships of the components of each of the different constructs used in the current study. Construction of these reporter vectors has been previously described. pA; SV40 polyadenylation sequence, lacZ; gene encoding β galactosidase marker protein, hβgprom; human beta globin promoter, TAC1prom; TAC1 promoter, ECR2; evolutionary conserved region 2, bent black arrow; indicates the transcriptional start site of the LacZ marker gene. B; bar graph demonstrating the proportion of primary DRG neurones that express βgal (as assayed using X-gal) following their transfection with pECR2-TAC1prom-LacZ and cultured in the presence of forskolin or KCl (n > 3, *;p < 0.05, n.s., not significant). Proportions are adjusted relative to a control plasmid containing the CMV promoter that was transfected at the same time to normalise transfection efficiencies. C, graphical analysis of the size distribution (diameter in microns) of neurones within ECR2-TAC1prom-LacZ transgenic DRG explants showing the proportion of cells expressing the β-gal before and after treatment with 30 mM KCl demonstrating a shift in the proportion of larger diameter cells expressing SP and the receptor (n = 3, No cells counted/measured = 201, *; p < 0.05).