Kinetics of acetylcholine quanta release at the neuromuscular junction during high‐frequency nerve stimulation

Abstract

The effects of high-frequency nerve stimulation (10-100 Hz) on the kinetics of evoked acetylcholine quanta secretion from frog motor nerve endings were studied. The amplitude and temporal parameters of uni-and multiquantal endplate currents were analysed to estimate the possible changes in the degree of synchrony of quantal release. The frog neuromuscular synapse is unusually long and we have placed special emphasis on evaluating the velocity of propagation of excitation along the nonmyelinated nerve ending as this might influence the synchrony of release from the whole terminal and hence affect the time course of postsynaptic currents. The data show that high-frequency firing leads to the desynchronization of acetylcholine release from motor nerve endings governed by at least two independent factors, namely a reduction of nerve pulse propagation velocity in the nonmyelinated parts of the axon and a change of secretion kinetics at single active zones. A computer reconstruction of the multiquantal synaptic response was performed to estimate any contribution of each of the above factors to the total rate of release and amplitude and time characteristics of the endplate currents. The results indicate that modification of the kinetics of neurotransmitter quanta release during high-frequency firing should be taken into account when mechanisms underlying the plasticity of chemical synapses are under investigation.

Electrophysiological characterization of sodium‐activated potassium channels in NG108‐15 and NSC‐34 motor neuron‐like cells

“…However, as high‐frequency firing in motor neurons has been reported to modify the kinetics of neurotransmitter quanta release (Kovyazina et al . , Maeno‐Hikichi et al . ), the resulting model presented here may be a framework used as a reference in the development of future models for the motor neuron.…”

Kinetics of neurotransmitter release in neuromuscular synapses of newborn and adult rats

“…, 2011). Also the frequency and number of nerve stimulation might influence the synaptic latency of a single quantum release (Kovyazina et al . , 2010).…”

“…, 2010). These changes in the kinetics of quanta secretion (or synaptic latencies) affect the amplitude and time course of the integral EPC and modulate the efficiency of synaptic transmission (Slater, 2008; Kovyazina et al . , 2010).…”

“…The kinetics of quantal release at the neuromuscular synapses can be regulated by various physiologically active compounds and their receptors (Samigullin et al, 2012), including cholinergic (Nikolsky et al, 2004), adrenergic (Bukcharaeva et al, 1999;Bukharaeva et al, 2002) and purinergic ones (Tsentsevitsky et al, 2011). Also the frequency and number of nerve stimulation might influence the synaptic latency of a single quantum release (Kovyazina et al, 2010). These changes in the kinetics of quanta secretion (or synaptic latencies) affect the amplitude and time course of the integral EPC and modulate the efficiency of synaptic transmission (Slater, 2008;Kovyazina et al, 2010).…”

“…Also the frequency and number of nerve stimulation might influence the synaptic latency of a single quantum release (Kovyazina et al, 2010). These changes in the kinetics of quanta secretion (or synaptic latencies) affect the amplitude and time course of the integral EPC and modulate the efficiency of synaptic transmission (Slater, 2008;Kovyazina et al, 2010).…”