Optical Recording of the Pacemaking Activity of a Congenital Double-heart in an Early Chick Embryo: (embryonic double-heart/pacemaking activity/optical monitoring/potential-sensitive dye).

A congenital double-hearted chick embryo was found among 16,171 embryos, which was at the 11 somite stage of development. The pacemaking activity of its double heart was monitored simultaneously from 9 different regions by optical methods. The right and left half hearts were tubular, and in both, spontaneous rhythmical action potentials and beating were detected, and differences were detected in their rhythms. Action potentials were also monitored in a malformed embryonic heart formed by partial fusion of the primordia. The results are discussed in relation to genesis of intrinsic pacemaking activity in cardiac primordia and to a spatial gradient of rhythmicity in the early stages of cardiogenesis.