Figure 7. Multiple to single innervation of the submandibular gland.
(A–B) Low magnification view of the parasympathetic innervation to P3 submandibular gland labeled by intra-uterine multicolor fluorescent protein AAV injection. The inset (B) and (C) shows an optical section through the gland where boutons of neurons expressing different color combinations of red and green fluorescent proteins are intermixed. The mixing contrasts with the segregation seen at later ages (see Figure 2). (C) Non-basket terminal in a P3 axon. (D) This tissue was also immuno-labeled for VAChT to reveal all the cholinergic parasympathetic terminals in the gland (red). (E) The non-basket terminal overlaps with other axons as demonstrated by the presence of red fluorescence that was not contained in the YFP labeled axon. (F) Occasional basket-shaped terminals are present in YFP-labeled P3 axonal arbors. In this case a branch of the ganglion cell axon (entering panel from the lower left) terminated in a basket-shaped arbor. (G) This tissue was also immuno-labeled for VAChT to reveal all the cholinergic parasympathetic terminals in the gland (as in D) (H) There was no evidence of any other parasympathetic axon within the region of the basket-shaped arbor because all the VAChT labeling was superimposed on the YFP labeled axon. Hence this terminal was segregated from other parasympathetic axons. Scale bar (A) 100 µm, (B) 20 µm. (C–H) 10 µm.