Ca2+ channels and synaptic transmission at the adult, neonatal, and P/Q-type deficient neuromuscular junction

Ann N Y Acad Sci. 2003 Sep:998:11-7. doi: 10.1196/annals.1254.003.

Abstract

Different types of voltage-activated Ca(2+) channels have been established based on their molecular structure and pharmacological and biophysical properties. One of them, the P/Q-type, is the main channel involved in nerve-evoked neurotransmitter release at neuromuscular junctions and the immunological target in Eaton-Lambert Syndrome. At adult neuromuscular junctions, L- and N-type Ca(2+) channels become involved in transmitter release only under certain experimental or pathological conditions. In contrast, at neonatal rat neuromuscular junctions, nerve-evoked synaptic transmission depends jointly on both N- and P/Q-type channels. Synaptic transmission at neuromuscular junctions of the ataxic P/Q-type Ca(2+) channel knockout mice is also dependent on two different types of channels, N- and R-type. At both neonatal and P/Q knockout junctions, the K(+)-evoked increase in miniature endplate potential frequency was not affected by N-type channel blockers, but strongly reduced by both P/Q- and R-type channel blockers. These differences could be accounted for by a differential location of the channels at the release site, being either P/Q- or R-type Ca(2+) channels located closer to the release site than N-type Ca(2+) channels. Thus, Ca(2+) channels may be recruited to mediate neurotransmitter release where P/Q-type channels seem to be the most suited type of Ca(2+) channel to mediate exocytosis at neuromuscular junctions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Adult
  • Aging / physiology*
  • Animals
  • Animals, Newborn
  • Calcium Channels, L-Type / drug effects
  • Calcium Channels, L-Type / metabolism
  • Calcium Channels, N-Type / classification
  • Calcium Channels, N-Type / deficiency
  • Calcium Channels, N-Type / physiology*
  • Fetus
  • Humans
  • Mice
  • Neuromuscular Junction / drug effects
  • Neuromuscular Junction / genetics
  • Neuromuscular Junction / physiology*
  • Neuromuscular Junction Diseases / physiopathology*
  • Neurotransmitter Agents / metabolism
  • Potassium / pharmacology
  • Rats
  • Synaptic Membranes / drug effects
  • Synaptic Membranes / metabolism
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology*

Substances

  • Calcium Channels, L-Type
  • Calcium Channels, N-Type
  • Neurotransmitter Agents
  • Potassium