Optical signals from early embryonic chick heart stained with potential sensitive dyes: evidence for electrical activity.
1. Using an optical method for monitoring membrane potential, spontaneous electrical activity in the very early embryonic chick heart at the 7-9 somite stages was measured. 2. Spontaneous absorption signals from the 7-8 somite embryonic chick hearts stained with a potential sensitive merocyanine-oxazolone dye were demonstrated. The signals were observed also when a merocyanine-rhodanine dye was used. These signals were identified as spontaneous electrical activity in the embryonic heart cells. 3. The action spectrum in absorption of the merocyanine-oxazolone dye was triphasic in early embryonic chick heart with an increase in transmittance from 750 to 700, a decrease from 700 to 600, and an increase from 600 to 525 nm. 4. The magnitude of the signal was about 10(-3) of the resting intensity at 675 nm, with the merocyanine-oxazolone dye. The spontaneous absorption signals had a signal-to-noise ratio of about 10, respectively. 5. The absorption signals were markedly depressed by a higher external K+-concentration, however, were not affected by tetrodotoxin (TTX). 6. The results indicate that spontaneous electrical activity is generated at the 7-9 somite developmental stage before the initiation of heartbeat.
D000042:Absorption; D000200:Action Potentials; D000818:Animals; D001583:Benzoxazoles; D002642:Chick Embryo; D004396:Coloring Agents; D006321:Heart / Q000196:embryology* / Q000502:physiology; D008564:Membrane Potentials; D010081:Oxazolone; D012236:Rhodanine / Q000031:analogs & derivatives; D013057:Spectrum Analysis; D013194:Staining and Labeling; D053778:Thiazolidines
D001583:Benzoxazoles; D004396:Coloring Agents; D053778:Thiazolidines; D010081:Oxazolone; C025279:merocyanine-rhodanine; D012236:Rhodanine