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Effect of calcium on excitatory neuromuscular transmission in the crayfish
Author(s) -
Bracho H.,
Orkand R. K.
Publication year - 1970
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1970.sp008997
Subject(s) - excitatory postsynaptic potential , neuromuscular junction , crayfish , electrophysiology , neurotransmission , biophysics , calcium , neuromuscular transmission , chemistry , extracellular , membrane potential , anatomy , neuroscience , biology , endocrinology , biochemistry , inhibitory postsynaptic potential , receptor , organic chemistry , fishery
1. The effects of varying the external Ca concentration from 1·8 to 30 m M /l. (⅛−2 times normal) have been studied at the in vitro crayfish excitatory neuromuscular junction. Electrophysiological techniques were used to record transmembrane junctional potentials from muscle fibres and extracellular junctional currents from the vicinity of nerve terminals. 2. The excitatory junctional potential amplitude was proportional to [Ca] 0 n , where n varied between 0·68 and 0·94 (mean 0·82) when [Ca] 0 was varied from 1·8 to 15 m M /l. 3. The increase in junctional potential amplitude on raising [Ca] 0 resulted primarily from an increase in the average number of quanta of excitatory transmitter released from the presynaptic nerve terminal by the nerve impulse. 4. The size of the quanta, synaptic delay, presynaptic potential and electrical properties of the muscle membrane were little affected by changes in calcium concentration in the range studied.