PARENT SESSION

(M352) ACETYLCHOLINE-INDUCED CA²⁺ TRANSIENT AND CA²⁺ CURRENT IN MOUSE EARLY EMBRYOS.

Kang, Dawon¹, Yoon, Sook-Young², Hong, Seong-Geun¹, Han, Jaehee¹, ¹ Gyeongsang National University, Jinju, South Korea² University of Massachusetts, Amherst, MA

ABSTRACT- In our previous study, acetylcholine (ACh) elicited Ca²⁺ oscillations via the m3/m4-PLC-IP3 pathway in the mouse oocytes. Studies have shown that ACh could cause early activation events in the mouse oocytes overexpressing muscarinic receptors. However, little is known about the physiological role of ACh during mouse embryonic development. We here report the effect of ACh on Ca²⁺ changes associated with the early development using whole-cell voltage clamp technique and confocal microscopy. During embryonic development, ACh had no effect on Ca²⁺ current, but changed Ca²⁺ transient. In 2-cell embryos, ACh elicited higher Ca²⁺ peak than in ovulated oocytes (Fluorescence intensity: 1898.0±423.5 in 2-cells, 1140.5±592.8 in oocytes, n=10). Interestingly, ACh significantly increased Ca²⁺ current (p<0.05), and elicited Ca²⁺ oscillations in ovulated oocytes, but not in early embryos. Furthermore, xestospongin-C, an IP3 receptor antagonist, suppressed intracellular Ca²⁺ transient peak in all stage eggs even though the inhibition rates were different. ACh also rescued in vitro culture 2-cell block in ICR strain mouse. These results suggest that ACh regulates intracellular Ca²⁺ during early embryonic development via different Ca²⁺ signal pathways from oocytes.

KEY WORDS: Acetylcholine, Ca²⁺ current, Ca²⁺ transient, Embryos