Involvement of Calcium Ions in Regulation of the Kinetics of the Release of Acetylcholine Quanta Forming Multiquantum Postsynaptic Responses

• Published in: Neuroscience and behavioral physiology 2013-06, Vol.43 (5), p.643-649
• Main Authors: Khuzakhmetova, V. F., Fatikhov, N. F., Bukharaeva, E. A., Nikol’skii, E. E.
• Format: Article
• Language: English
• Subjects: Acetylcholine; Anura; Behavioral Sciences; Biomedical and Life Sciences; Biomedicine; Digitization; Experiments; Neurobiology; Neurosciences; Physiology; Transmitters
• ISSN: 0097-0549; 1573-899X
• DOI: 10.1007/s11055-013-9785-1

Experiments on frog neuromuscular synapses using the “sequential subtraction” method developed in our laboratory were performed to investigate the quantum composition of endplate currents and the time parameters of the release of acetylcholine quanta forming multiquantum postsynaptic responses in the presence of varying calcium ion levels. These experiments showed that at physiological levels of transmitter release in response to application of single stimuli of the motor nerve, quanta were released asynchronously, as indicated by the nature of fluctuations in the latent periods of single-quantum responses forming the complete quantum signal. Different reactions in terms of the quantum composition of endplate currents and the kinetics of quantum release were seen when the extracellular calcium ion concentration was increased: quantum composition increased exponentially with increases in calcium concentration from 0.4 to 1.8 mM, while the synchronicity of quantum release reached a peak at a calcium concentration of 1.0 mM. These data lead to the conclusion that changes in the synchronicity of transmitter quantum release in response to each nerve impulse in conditions of modified calcium influx into nerve terminals can be regarded as one of the mechanisms mediating synaptic plasticity.