Cardiac neural crest ablation alters aortic smooth muscle force and voltage-sensitive Ca2+ responses.

Ablation of the premigratory cardiac neural crest (CNC) from the chick embryo results in a malformed outflow tract vasculature termed persistent truncus arteriosus (PTA). In addition, loss of the CNC disrupts myocardial excitation-contraction (EC) coupling, decreases intracellular Ca2+ transients, and depresses force generation. We examined if similar defects occurred in the neural crest-derived smooth muscle of the aortic arch in a test of the hypothesis that loss of elements from the CNC disrupts EC coupling and force production in the smooth muscle of the tunica media of the aortic arch. Aortic arch segments from chicks (embryonic day 15) displaying PTA generated approximately 43% of stress generated by the aortic arch from sham-operated control embryos during potassium depolarization. The depressed force response was associated with a twofold lower Fura-2 transient. In contrast, force and steady-state Fura-2 signals during endothelin-1 stimulation were unchanged. The differences seen in stress generation with potassium depolarization between sham and PTA displaying embryos were not seen in the descending aorta, a tissue not derived from the neural crest. Protein content and immunostaining revealed no differences in the content of actin, myosin, or dihydropyridine receptor from sham or PTA aortic arch. Our results suggest that the CNC is required for normal aortic arch smooth muscle function and support the hypothesis that the loss of CNC impacts the force generating ability, in part by disruption of the EC-coupling processes and altering Ca(2+)-handling.