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Dopaminergic modulation of neuromuscular transmission in the prawn.
Author(s) -
Miller M W,
Parnas H,
Parnas I
Publication year - 1985
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.1985.sp015716
Subject(s) - dopamine , excitatory postsynaptic potential , dopaminergic , chemistry , biophysics , neuromuscular junction , electrophysiology , resting potential , neuroscience , dopamine receptor , neurotransmission , facilitation , extracellular , endocrinology , biology , inhibitory postsynaptic potential , receptor , biochemistry
The action of the putative crustacean neurohormone dopamine was examined in the fast extensor musculature of the prawn with intracellular and extracellular recording techniques. Dopamine produced a concentration‐dependent (10(‐7)‐10(‐5) M) decrease in the size of the excitatory junctional potential (e.j.p.). It had no effect on the muscle fibre resting membrane potential or input resistance. High concentrations (10(‐5)M) of dopamine had no effect on the amplitude distribution or decay time of quantal unit currents, indicating that the agent does not act by blocking post‐synaptic receptors or channels. Bath application of dopamine reduced the quantal content at single release sites with a similar time course and concentration dependence as that observed for the e.j.p. Dopamine had no effect on histograms of synaptic delays determined over a 10 degree C range, indicating that it does not modify the time course of phasic neurosecretion. Twin‐impulse facilitation experiments showed a marked decrease in the duration of facilitation in the presence of dopamine. These results are interpreted according to recent theoretical and experimental findings as indicating that the dopamine‐induced reduction in transmitter release is produced by a decrease in the entry of Ca during the nerve terminal action potential.