Electrical and optical study of nerve impulse-evoked ATP-induced, P2X-receptor-mediated sympathetic neurotransmission at single smooth muscle cells in mouse isolated VAS deferens

Neuroscience. 2007 Aug 10;148(1):82-91. doi: 10.1016/j.neuroscience.2007.05.044. Epub 2007 Jul 16.

Abstract

Simultaneous electrophysiology and confocal microscopy were used to investigate purinergic neurotransmission at single smooth muscle cells (SMCs) in mouse isolated vas deferens, and to explore the relationship between two high-resolution P2X-receptor-mediated measures of per pulse ATP release: transient peaks in the first time derivative of the rising phase of excitatory junction potentials (EJPs) recorded in single SMCs ('discrete events'; DEs) and neuroeffector Ca(2+) transients (NCTs) in the impaled SMCs. This study shows that discrete events represent neurotransmitter release onto the impaled cell. First, the median amplitude of the first derivative of the EJP was larger when there was a coincident NCT in the impaled cell, compared with instances when no coincident NCT occurred. Second, the time-to-peak amplitude of the first derivative was shorter if there was a coincident NCT in the impaled cell, compared with when no coincident NCT was observed within the field. Surprisingly, first derivative amplitude increased with the distance (of the corresponding NCT) from the microelectrode. The microelectrode did not locally inhibit the functional quantal size as there was no effect of distance on the normalized NCT amplitude. When the significant effect of distance (between the microelectrode and NCTs) on the first derivative amplitude was removed, there was no correlation between the unstandardized residual (of distance vs. first derivative amplitude) and NCT amplitude. The absence of a correlation between DE and NCT amplitudes suggests that the NCT amplitude is a poor measure of quantal size. The usefulness of NCTs hence lies primarily in locating neurotransmitter release and measuring changes in local release probability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Adenosine Triphosphate / pharmacology
  • Animals
  • Calcium Signaling / drug effects
  • Calcium Signaling / physiology
  • Electrophysiology / methods
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Confocal
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism*
  • Neurotransmitter Agents / metabolism
  • Organ Culture Techniques
  • Presynaptic Terminals / metabolism
  • Receptors, Purinergic P2 / metabolism*
  • Receptors, Purinergic P2X
  • Sympathetic Fibers, Postganglionic / drug effects
  • Sympathetic Fibers, Postganglionic / metabolism*
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology*
  • Synaptic Vesicles / metabolism
  • Time Factors
  • Vas Deferens / innervation
  • Vas Deferens / metabolism*

Substances

  • Neurotransmitter Agents
  • Receptors, Purinergic P2
  • Receptors, Purinergic P2X
  • Adenosine Triphosphate