LINEAGE AND DEVELOPMENT OF THE PARASYMPATHETIC NERVOUS-SYSTEM OF THE EMBRYONIC CHICK HEART

We were interested in the contribution of the cardiac neural crest to the complete anterior and posterior nerve plexus of the chick heart. T his includes the pathways by which these cardiac neural crest-derived neuronal precursors enter the heart. As lineage techniques we used the traditional quail-chick chimera in combination with the newly introdu ced technique of retroviral reporter gene transfer to premigratory car diac neural crest cells. Retrovirally infected embryos (n=23) and quai l-chick chimeras (n=19) between stages HH27 and 40, were immunohistoch emically evaluated, using the lineage markers LacZ (retroviral reporte r) and QCPN (anti-quail nuclear marker), respectively and the neuronal differentiation markers HNK-1, RMO-270 and DO-170. Between stages HH2 7 and 33, quail-derived and LacZ positive cells were situated around t he arterial cardiac vagal branches at the arterial pole, and vagal bra nches along the anterior cardinal veins and the sinal vagal branch at the venous pole. From stage HH35 onward, QCPN/LacZ-positive cardiac ga nglia were observed throughout the anterior and posterior plexus and w ere mainly concentrated in the subepicardium near the distal ends of t he arterial cardiac vagal branches and the sinal cardiac vagal branch respectively. From stage HH36 both the anterior and posterior plexus c ontained a population of large cardiac ganglion cells and a population of smaller cells along nerve branches as well as in the cardiac gangl ia, which means that differentiation starts in both plexus at the same time. Furthermore only nerve fiber connections between the anterior a nd posterior plexus were observed. These results show that the cardiac neural crest contributes to the cardiac ganglion cells from both the entire anterior and posterior plexus. Furthermore these results sugges t that these precursor cells enter the arterial pole via the arterial cardiac vagal branches and the venous pole via the sinal cardiac vagal branch without intermixing. Finally we show that in addition to the c ardiac ganglia, the cardiac neural crest contributes to small myocardi al glia or undifferentiated cells along nerve fibers, and some myocard ial nerve fibers as well as nerve tissue in the adventitia of the larg e veins at the venous pole and in the adventitia of the coronary arter ies.