Nodose placode contributes autonomic neurons to the heart in the absence of cardiac neural crest.

The objective of this research was to determine the origin of the cholinergic neurons that populate the heart following ablation of the neural crest area, which normally gives rise to the cardiac ganglia. Using ablation of various areas of surface ectoderm--including neural crest migrating to the heart, nodose placode, and neural crest plus nodose placode--it was determined that regeneration of the neural component of cardiac neural crest did not occur in the absence of the nodose placodes. When cells from the nodose placode were followed in quail to chick chimeras of nodose placode with ablated cardiac neural crest, quail nodose placode-derived neurons were found in the cardiac ganglia. These results explain the "regeneration" of cholinergic cardiac ganglia in embryos lacking cardiac neural crest.