Chlorotoxin-mediated disinhibition of noradrenergic locus coeruleus neurons using a conditional transgenic approach

Brain Res. 2004 Jul 30;1016(1):20-32. doi: 10.1016/j.brainres.2004.03.078.

Abstract

The noradrenergic locus coeruleus (LC) has been implicated in the promotion of arousal, in focused attention and learning, and in the regulation of the sleep/waking cycle. The complex biological functions of the central noradrenergic system have been investigated largely through electrophysiological recordings and neurotoxic lesions of LC neurons. Activation of LC neurons through electrical or chemical stimulation has also led to important insights, although these techniques have limited cellular specificity and short-term effects. Here, we describe a novel method aimed at stimulating the central noradrenergic system in a highly selective manner for prolonged periods of time. This was achieved through the conditional expression of a transgene for chlorotoxin (Cltx) in the LC of adult mice. Chlorotoxin is a component of scorpion venom that partially blocks small conductance chloride channels. In this manner, the influence of GABAergic and glycinergic inhibitory inputs on LC cells is greatly reduced, while their ability to respond to excitatory inputs is unaffected. We demonstrate that the unilateral induction of Cltx expression in the LC is associated with a concomitant ipsilateral increase in the expression of markers of noradrenergic activity in LC neurons. Moreover, LC disinhibition is associated with the ipsilateral induction of the immediate early gene NGFI-A in cortical and subcortical target areas. Unlike previous gain of function approaches, transgenic disinhibition of LC cells is highly selective and persists for at least several weeks. This method represents a powerful new tool to assess the long-term effects of LC activation and is potentially applicable to other neuronal systems.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / metabolism
  • Animals
  • Cells, Cultured
  • Chlorides / metabolism
  • Embryo, Mammalian
  • Fibroblasts / physiology
  • Fibroblasts / virology
  • Fluorescent Dyes / metabolism
  • Genes, Reporter / physiology
  • Immunohistochemistry / methods
  • In Vitro Techniques
  • Integrases / metabolism
  • Locus Coeruleus / cytology*
  • Locus Coeruleus / physiology
  • Locus Coeruleus / virology
  • Membrane Potentials / drug effects
  • Mice
  • Mice, Transgenic
  • Neural Inhibition / drug effects*
  • Neural Inhibition / physiology
  • Neurons / drug effects*
  • Neurons / physiology
  • Neurons / virology
  • Norepinephrine / metabolism*
  • Norepinephrine Plasma Membrane Transport Proteins
  • Patch-Clamp Techniques / methods
  • RNA, Messenger
  • Repressor Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Scorpion Venoms / pharmacology*
  • Stilbamidines / metabolism
  • Symporters / metabolism
  • Synapses / drug effects
  • Transfection / methods
  • Tyrosine 3-Monooxygenase / metabolism
  • gamma-Aminobutyric Acid / pharmacology

Substances

  • 2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt
  • Chlorides
  • Fluorescent Dyes
  • Nab1 protein, mouse
  • Norepinephrine Plasma Membrane Transport Proteins
  • RNA, Messenger
  • Repressor Proteins
  • Scorpion Venoms
  • Slc6a2 protein, mouse
  • Stilbamidines
  • Symporters
  • Chlorotoxin
  • gamma-Aminobutyric Acid
  • Tyrosine 3-Monooxygenase
  • Cre recombinase
  • Integrases
  • Norepinephrine