Vagal Fibers Form Associations With Interstitial Cells of Cajal During Fetal Development

Vagal intramuscular arrays (IMAs) have been shown to form complexes with intramuscular interstitial cells of Cajal (ICC). We tested the hypothesis that associations between vagal nerve endings and ICC arise in fetal development. Intraganglionic laminar endings (IGLEs) and IMAs were identified by applying 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanineperchlorate (DiI) to vagal nerve trunks and myenteric plexus (MP) and intramuscular (IM) ICC were immunolabeled with antibodies to c-Kit in fetal and early postnatal mice (E16-P7). At E16, c-Kit immunoreactive cells were abundant in the primordial smooth muscle, with early ICC networks discernable by E18 and ongoing organization at P1 and P7. The distribution of vagal endings was found to change during the course of development, with significantly more putative IGLEs in the prenatal compared to the postnatal period and less IMAs in the prenatal compared to postnatal period. Associations of ICC with both IGLEs and IMAs were detected as early as E16 and were maintained into postnatal life. These findings suggest that vagal fibers begin to associate with ICC during prenatal development. Future studies will be needed to determine the mechanisms through which vagal endings and ICC interact.