Single-cell RT-PCR and functional characterization of Ca2+ channels in motoneurons of the rat facial nucleus

J Neurosci. 1998 Dec 1;18(23):9573-84. doi: 10.1523/JNEUROSCI.18-23-09573.1998.

Abstract

Voltage-dependent Ca2+ channels are a major pathway for Ca2+ entry in neurons. We have studied the electrophysiological, pharmacological, and molecular properties of voltage-gated Ca2+ channels in motoneurons of the rat facial nucleus in slices of the brainstem. Most facial motoneurons express both low voltage-activated (LVA) and high voltage-activated (HVA) Ca2+ channel currents. The HVA current is composed of a number of pharmacologically separable components, including 30% of N-type and approximately 5% of L-type. Despite the dominating role of P-type Ca2+ channels in transmitter release at facial motoneuron terminals described in previous studies, these channels were not present in the cell body. Remarkably, most of the HVA current was carried through a new type of Ca2+ channel that is resistant to toxin and dihydropyridine block but distinct from the R-type currents described in other neurons. Using reverse transcription followed by PCR amplification (RT-PCR) with a powerful set of primers designed to amplify all HVA subtypes of the alpha1-subunit, we identified a highly heterogeneous expression pattern of Ca2+ channel alpha1-subunit mRNA in individual neurons consistent with the Ca2+ current components found in the cell bodies and axon terminals. We detected mRNA for alpha1A in 86% of neurons, alpha1B in 59%, alpha1C in 18%, alpha1D in 18%, and alpha1E in 59%. Either alpha1A or alpha1B mRNAs (or both) were present in all neurons, together with various other alpha1-subunit mRNAs. The most frequently occurring combination was alpha1A with alpha1B and alpha1E. Taken together, these results demonstrate that the Ca2+ channel pattern found in facial motoneurons is highly distinct from that found in other brainstem motoneurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Brain Stem / cytology
  • Cadmium / pharmacology
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / genetics*
  • Calcium Channels, L-Type
  • DNA, Complementary
  • Dihydropyridines / pharmacology
  • Facial Nerve / chemistry
  • Facial Nerve / cytology*
  • Ion Channel Gating / drug effects
  • Motor Neurons / chemistry*
  • Nickel / pharmacology
  • Nitrendipine / pharmacology
  • Patch-Clamp Techniques
  • Peptides / pharmacology
  • RNA, Messenger / analysis
  • Rats
  • Rats, Wistar
  • Receptors, Cholinergic / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Spider Venoms / pharmacology
  • omega-Agatoxin IVA
  • omega-Conotoxin GVIA
  • omega-Conotoxins*

Substances

  • Calcium Channel Blockers
  • Calcium Channels
  • Calcium Channels, L-Type
  • DNA, Complementary
  • Dihydropyridines
  • Peptides
  • RNA, Messenger
  • Receptors, Cholinergic
  • Spider Venoms
  • omega-Agatoxin IVA
  • omega-Conotoxins
  • Cadmium
  • omega-conotoxin-MVIIC
  • Nickel
  • omega-Conotoxin GVIA
  • Nitrendipine