Endogenous electrical currents and the resultant voltage gradients in the chick embryo

• Published in: Developmental biology Vol. 140; no. 1; pp. 149 - 160
• Main Authors: Hotary, Kevin B., Robinson, Kenneth R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.07.1990; Elsevier
• Subjects: Amiloride - pharmacology; ANIMAL EMBRYOS; Animals; Biological and medical sciences; Calcium - pharmacology; Chick Embryo - physiology; chick embryos; CHICKS; Chlorine - pharmacology; DESARROLLO EMBRIONARIO; DEVELOPPEMENT EMBRYONNAIRE; Electric Conductivity; ELECTRICIDAD; ELECTRICITE; ELECTRICITY; Electrophysiology; EMBRIONES ANIMALES; Embryology: invertebrates and vertebrates. Teratology; EMBRYON ANIMAL; EMBRYONIC DEVELOPMENT; Fundamental and applied biological sciences. Psychology; Membrane Potentials - drug effects; Microscopy, Electron, Scanning; Organogenesis. Fetal development; Organogenesis. Physiological fonctions; POLLITO; POUSSIN; Sodium - pharmacology; voltage; Embryonic development; Vertebrata; Gradient; Transepithelial potential; Electric field; Digestive system; Gut; Electrophysiology; Chicken; Aves; Outward current; Electric current
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/0012-1606(90)90062-N

We have studied some of the electrophysiological properties of 2 1 2 - to 4-day-old (stage 14–22) chick embryos. Using a recently developed two-dimensional vibrating probe, large currents were found to exit the posterior intestinal portal (p.i.p.) during the period of tail gut reduction. During this period, epithelial cells lining cloacal regions of the hindgut are dying, thus creating a low-resistance pathway for current flow out of the embryo. Currents entered the intact epithelium over other regions of the embryo. The outward currents at the p.i.p. were first detected at stage 15 and reached their average maximum current density of 112 ± 10 μA/cm 2 at stage 17. After stage 17, the magnitude of the currents decreased, dropping to 16 ± 0.3 μA/cm 2 by stage 22. The currents were reversibly reduced by about 50% when Na + was replaced by choline in the bathing solution. The magnitude of the currents leaving the p.i.p. suggested the existence of a measurable intraembryonic voltage gradient. The transepithelial potential (TEP) of stage 14–21 embryos was measured lateral to the neural tube through the dorsal ectoderm. For all stages, the combined average TEP was 16 ± 0.5 mV. Differences in the TEP between various regions of the embryo were used to calculate an intraembryonic voltage gradient. At stage 14, before outward current was found at the p.i.p., no significant intraembryonic voltage gradient was detected. At stage 17, when the outward current at the p.i.p. was maximum, a voltage gradient of 21 ± 5 mV/mm (mean ± SEM; N = 6) was measured in the caudal end of the embryo. This gradient in some cases was as steep as 33 mV/mm. This is well above the minimum level needed to affect the direction of embryonic cell migration in vitro. We hypothesize that this endogenous electrical field acts as a directional cue for neural crest cell movements in the developing chick embryo.