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.