Embryonic Heart Tube Research Articles

Patterns of reversal in the heart of Ciona intestinalis L.

The reversal of the heart beat is not exclusive to tunicates, for Marcello Malpighi in 1660 described periodic reversal in Bombyx mori and in some Orthoptera. In 1821 Kuhl and van Hasselt reported the phenomenon in Ciona intestinalis L. We have observed reversal in many active pulsating blood vessels, both in vertebrates and in invertebrates, and even in embryonic heart tubes. Using four or five suction electrodes simultaneously, we were able to record electrical activity from multiple sites. Normally, the contraction wave originates from a localized site at one end of the tube and then traverses the whole length of the heart. When a wave of excitation does not propagate the full length, the blocked area may initiate a wave that then travels opposite to the initial direction (contrawave). This pattern, where activity arises in two separate areas such that the one contractile wave is orthograde and the other retrograde, may persist for a prolonged period. Each different pattern seems to result from some disturbance of the normal pacemaker in the myoepithelial cells.