Double-label fluorescent in situ hybridizations were used to examine the expression of T2Rs with gustducin and T1Rs. (a) T2Rs are expressed in the same cells as (b) gustducin, as shown in (c) where the two-channel fluorescent image (1mm optical section of a rat circumballate papilla) is overlaid on a difference interference contrast image.  The dotted lines outline the approximate area of labeled taste receptor cells; arrows indicate gustducin-expressing cells that do not contain T2Rs.  In contrast, (d) shows that T1Rs (red) are expressed in different subset of taste receptor cells from T2Rs (green).