title: Dopaminergic modulation of neuromuscular transmission in the prawn.
abstract: 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.
authors.forename: M W
authors.initials: MW
authors.lastname: Miller
authors.forename: H
authors.initials: H
authors.lastname: Parnas
authors.forename: I
authors.initials: I
authors.lastname: Parnas
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D033364:Decapoda / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology*; D007700:Kinetics; D009469:Neuromuscular Junction / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000502:physiology; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects*; D013997:Time Factors
chemical_list: D018377:Neurotransmitter Agents; D004298:Dopamine