We first used the
gpa-16 promoter (Jansen et al., 1999) to broadly drive the expression of GCaMP3 in pharyngeal muscle. We characterized the expression pattern of this transgene using confocal microscopy and observed bright fluorescence in the
pm2 and
pm3 muscles and also in the
mc1 marginal cells. We also observed occasional dim fluorescence in
pm1 (3 of 10 animals).