Contribution of Ryanodine Receptors in Forming Presynaptic Ca~(2+) Level and Cholinergic Modulation in Response to Single Potential in Frog Neuromuscular Junction

摘要

Ca~(2+) entering through voltage-gated Ca~(2+) channels plays a key role in the initiation of neurotransmitter secretion. However, intracellular Ca~(2+) storages such as endoplasmic reticulum (ER) can also contribute in the presynaptic Ca~(2+) level forming. Also ryanodine-dependent Ca~(2+)-induced Ca~(2+) channels of endoplasmic reticulum may contribute in secretion inhibiting action of cholinomimetics. In this work, we use a photometric method for estimating the relative change in the level of presynaptic Ca~(2+) ions (Ca~(2+) transient). We have shown that during low-frequency stimulation Ca~(2+) release from the ER is involved in forming of presynaptic Ca~(2+) level. And more likely those effects of the cholinomimetics on Ca~(2+) transient are not related to Ca~(2+) release from the endoplasmic reticulum.