Neomycin and U73122 are known to suppress inositol 1,4,5-trisphosphate (InsP3) production by inhibition of phospholipase C. We studied the effects of these inhibitors on the excitatory currents, I(ex), in Chara corallina under voltage-clamp conditions. Computer simulations of the experimental effects by a minimum model for the excitatory reaction pathway allow the assignment of the inhibitory effects to one specific reaction step, i.e. the release of Ca2+ from InsP3-sensitive internal stores. In contrast, the inhibitory effect of La3+ on I(ex) suggests inactivation of Cl- channels. Furthermore, ryanodine-sensitive Ca2+ stores seem to be irrelevant for electrical excitation in Chara.
Biskup, B., Gradmann, D., & Thiel, G. (1999). Calcium release from InsP3-sensitive internal stores initiates action potential in Chara. FEBS Letters, 453(1–2), 72–76. https://doi.org/10.1016/S0014-5793(99)00600-6