Fig. 2. Distribution of GABA-positive fibers on the various components of the salivary gland complex. Whole-mount preparations of salivary glands were stained with anti-GABA (green) and AlexaFluor488-phalloidin (blue), and imaged by confocal microscopy. (A) A simplified schematic illustration of the organization of the salivary gland complex. The paired salivary glands consist of lobules of acinar tissue. The salivary ducts unite to an efferent salivary duct (1) from each gland, and the two efferent salivary ducts unite to a single main salivary duct (2). The paired reservoirs open into reservoir ducts (3) that unite to the main reservoir duct (4). Red rectangles in A outline the areas shown in B–E. (B) The salivary duct nerve (SDN) contains two thick axons, one of them labeled by anti-GABA. (C) Anti-GABA-immunoreactive fibers (arrowheads) in the reservoir muscle. (D) A nerve that interlinks an acinar lobule (lower right) with the reservoir (asterisks). Anti-GABA-positive fibers (arrowheads) branch and have numerous varicosities within the nerve. (E) An acinar lobule and the associated salivary duct (arrow). P-cells are arranged in pairs with their microvilli intensely stained with phalloidin (blue), providing the appearance of `bow ties'. A loose network of anti-GABA-reactive fibers is associated with the acinar tissue but not the salivary duct (arrow). (F–H,J–L) Two series of confocal sections through acinar lobules. Each image shows the sum of 17 consecutive optical sections, representing a total thickness of 6.2 µm. The labelling in the upper right indicates the plane of the optical section. (I,M) The sum of all images. P-cells are indicated by asterisks. C-cells in the interior of the acinar lobules are identified by short phalloidin-stained microvilli (open arrowheads). In the lobule shown in (F–I), GABA-positive fibers remain and terminate (arrowhead in G) on the surface of the lobule. In (J–M), GABA-positive fibers extend deep into the acinar lobules (arrows). All bars, 50 µm; bar in M is for F–M.