Figure 9.

Double-labeling experiments illustrate relations between catecholaminergic and serotonergic innervation of the foregut. A: Image of the pharynx region labeled for THli (green) and 5HTIi (red). Several small THli cell bodies were observed (two indicated by arrowheads). Although no serotonergic somata were detected, several cell bodies were enveloped by varicose serotonergic fibers (two indicted by arrows). No TH-5HTIi double-labeled fibers or cell bodies were observed. Moreover, serotonergic somatic innervation was not found to occur on THli neurons. B: Overlay image of biocytin fill (red) of En₂ toward the pharynx and THli (green). Although the majority of the THli cells in the pharynx did not exhibit double labeling, THli was occasionally detected in pharyngeal neurons that had afferent En projections (cell appears yellow in overlay image, arrow). C: Biocytin fill (red) of En₂ toward the pharynx overlayed with 5HTli (green). No double labeling was observed, but several filled peripheral cell bodies were enveloped with serotonergic fibers (two indicated by arrow), indicative of serotonergic regulation of CNS afferents. Magenta/green images submitted as Supporting Information Figure 3 Scale bar = 100 μm.