ISSN:
1573-899X
Keywords:
Neuromuscular synapse
;
modulation of evoked secretion
;
synchronization of secretion of mediator quanta
;
noradrenaline
;
adrenoceptors
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract Experiments on frog neuromuscular junction preparations with extracellular recording of nerve terminal action potentials and single-quantum end-plate currents (EPC) were used to assess the time course of evoked quantum secretion of mediator by analyzing histograms of the distribution of true synaptic delays. These studies showed that noradrenaline, isoproterenol, and dobutamine change the kinetics of secretion of quanta, leading to synchronization of the process of mediator release; substances blocking β-adrenoceptors (atenolol, propranolol) blocked this effect. Clonidine and phenylephrine, which activate α-receptors, had no effect on the kinetics of secretion, while the α-blocker phentolamine had no effect on the synchronizing action of noradrenaline. Reconstruction of multiquantum EPC from changes in the level of synchronization in the release of individual quanta, showed that EPC amplitude increased in response to noradrenaline by 17%, and that this was due only to alterations in the time course of secretion. These data led to the conclusion that these is a special presynaptic mechanism which facilitates the action of sympathomimetics, acting via β-adrenoceptors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02463151
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