Optical studies of excitation‐contraction coupling in the early embryonic chick heart.

Abstract

SUMMARY1. Excitation-contraction coupling at the onset of beating in the 9-10-somite embryonic chick heart was studied by means of an optical method together with a voltage-sensitive merocyanine-rhodanine dye. Spontaneous optical signals were recorded simultaneously from many areas of the embryonic heart, using a square photodiode matrix array.2. At time of initiation of the heartbeat, spontaneous optical signals consisting of two components were often detected. The first component (1st signal) is a dye-related absorption change due to the action potential, and the second component (2nd signal) is a light scattering change due to contraction.3. When Ca2+ in the bathing solution was partly replaced by Mg2+, the peak size of both signals was reduced. The correlation between the 1st and 2nd signals corresponded to the relationship between excitation and contraction.4. The formation of excitation-contraction coupling exhibited a regional nonuniformity in the developing 9-10-somite embryonic hearts: contraction was first generated in the right ventricular region, and then the contractile area spread widely over the whole of the heart. The curves of the excitation-related 1st signal vs. the contraction-related 2nd signal obtained from different areas were not superimposable.5. Decoupling of excitation from contraction was produced by raising the Ca2+ concentration in the bathing solution, by lowering the Na2+ concentration or by inclusion of a Ca21 ionophore (A23187). Replacement of the bathing solution with D20 or hypertonic solution also suppressed excitation-contraction coupling.6. The results suggest that in the early embryonic initial beating chick heart, the contractile system is activated by Ca2+ influx across the sarcolemma accompanying the action potential, and that a Na+-Ca2+ exchange mechanism participates in the relaxation phase of the heartbeat.

Ultrahigh-speed optical coherence tomography imaging and visualization of the embryonic avian heart using a buffered Fourier Domain Mode Locked laser

“…The contractile wave propagation in the proximal heart tube is measured to be 4.5 times faster than wave propagation in the distal heart tube at very early stages of development. While differences in wave propagation down the length of the heart tube have been demonstrated previously using measurements of electrical conduction [42][43][44], OCT imaging demonstrates the ability to quantify the mechanical wave in vivo, non-invasively, and without the addition of contrast agents or surrogate markers. In the future by combining gated imaging with an ultrahigh-speed OCT system, the contractile wave can be measured on a 3D + time data set, which will provide a more accurate measurement.…”

Conduction pattern of excitation in the amphibian atrium assessed by multiple-site optical recording of action potentials.

“…When we optically monitor action potentials from contractile tissues using voltage-sensitive dyes, optical changes generally include light-scattering changes due to mechanical movement (BAYLOR and OETLIKER, 1977;VERGARA and BEZANILLA, 1976;MORAD and SALAMA, 1979;SAWANOBORI et al, 1981;KASS, 1981;HIROTA et al, 1985a). Accordingly, in a strongly beating heart stained with voltagesensitive dyes, action potential-related optical signals are often covered by a larger mechanical movement artifact.…”

Optical Mapping Approaches to Cardiac Electrophysiological Functions.

“…The contraction artifact with a moderate size, which is due to light-scattering changes of the preparation, can be used as an index of the contractility of the cardiac muscle. By comparing the action potential-related component and the contraction-related component of the optical signals, we studied the characteristics of excitation-contraction coupling in the early embryonic heart [81].…”