[Statistical analysis of calcium accumulation in nerve endings during rhythmic stimulation]

The extracellular recording was used to examine the evoked transmitter release in neuromuscular junctions of the frog sartorius muscle at pair and repetitive stimulations. The repetitive stimulation with low initial level of secretion (the quantum content 0.1-0.5) led to the increased transmitter release. Statistical analysis showed that the probability of the quantum transmitter release in response to each stimulus was increased. The method of conditioned probabilities revealed a decrease in the probability of the quantum release provided the previous stimulus had induced the secretion of the acetylcholine quantum. It is assumed that at the moment of the quantum transmitter release (or promptly after it) a certain quantity of Ca2+ leaves the nerve terminal cytoplasm, thereby significantly reducing the intracellular concentration of calcium.