In mouse motor nerve terminals activation of Ca²⁺ channels and ryanodine receptors creates Ca²⁺ signals that are different in dynamic and modality. Pattern of these Ca²⁺ signals, leading to individual changes in mediator secretion is unclear. An effective approach to solve this problem is the use of Ca²⁺ buffers to discriminate Ca²⁺ signals created by different Ca²⁺ searches. The aim of this research was to study changes in mediator release caused by activation of Ca²⁺ channels or ryanodine receptors in conjunction with different Ca²⁺ buffers. Experiments were carried out on the dissected neuromuscular preparation of mouse diaphragm. Evoked endplate potentials (EPPs) were registered in response to unitary (0,3 Hz) nerve stimulation using standard microelectrode technique and then quantal content (QC) of unitary EPPs was analyzed. We used intracellular Ca²⁺ buffers BAPTA-AM and EGTA-AM (50 microM), BAY K 8644 (1 microM), caffeine (2.5 mM). Activation of presynaptic (P/Q type) Ca²⁺ channels in response to nerve stimulation leads to generation of EPPs with QC of 21.32±0.4 (n=93). The L-type Ca²⁺ channel activator BAY K 8644 (1 microM) showed a 18.7±4.72% increase of QC of EPPs (n=16, p<0,05, t-test). Application of ryanodine receptors agonist caffeine (2.5 mM) created a 12.9±4.32% increase of EPPs QC in comparison to control level (n=33, p<0.05, t-test). Loading terminal with fast Ca²⁺ buffer BAPTA-AM (50 microM) did not affect QC, but slow buffer EGTA-AM (50 microM) led to a 13±5.96% decrease of this parameter (n=15, p<0,05, t-test). BAPTA-AM didn’t affect effects of BAY K 8644, but EGTA-AM prevented the increase of QC of EPPs induced by BAY K 8644. In this case QC was 83.94±5.96% compared to control (n=15, p<0,05, t-test). Both Ca²⁺ buffers prevented the increase of EPPs QC initiated by caffeine (2.5 mM). It’s important to note that in EGTA-loaded terminals there was no significant difference in QC between control and caffeine effect, while EGTA-AM itself decreased this parameter. So, we found, that the increase of acetylcholine secretion after activation of different calcium inputs can be influenced by Ca²⁺ buffers, but demonstrates individual patterns of sensitivity to EGTA and BAPTA. Selective action of EGTA but not BAPTA preventing QC increase created by activation of P/Q or L-type channels allows us to suggest that activation of Ca²⁺ channels leads to slow and local elevation of Ca²⁺ concentration in nerve terminals. In contrary, similar efficacy of both Ca²⁺ buffers in preventing caffeine effects gives evidence that activation of ryanodine receptors is associated with tonic increase of intracellular Ca2²⁺ level which influences high sensitive Ca²⁺ sensors, controlling mediator secretion.