Dopaminergic modulation of neuromuscular transmission in the prawn.
AUTOR(ES)
Miller, M W
RESUMO
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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1192935Documentos Relacionados
- Modulation of neuromuscular transmission by endogenous and exogenous prostaglandins in the guinea-pig mesenteric artery
- Neuromuscular transmission in the 17th century
- Neuromuscular transmission at newly formed neuromuscular junctions in the regenerating soleus muscle of the rat.
- AUTONOMIC NEUROMUSCULAR TRANSMISSION
- Sources of adenosine released during neuromuscular transmission in the rat.