Reversal of pathological pain through specific spinal GABAA receptor subtypes

Nature. 2008 Jan 17;451(7176):330-4. doi: 10.1038/nature06493.

Abstract

Inflammatory diseases and neuropathic insults are frequently accompanied by severe and debilitating pain, which can become chronic and often unresponsive to conventional analgesic treatment. A loss of synaptic inhibition in the spinal dorsal horn is considered to contribute significantly to this pain pathology. Facilitation of spinal gamma-aminobutyric acid (GABA)ergic neurotransmission through modulation of GABA(A) receptors should be able to compensate for this loss. With the use of GABA(A)-receptor point-mutated knock-in mice in which specific GABA(A) receptor subtypes have been selectively rendered insensitive to benzodiazepine-site ligands, we show here that pronounced analgesia can be achieved by specifically targeting spinal GABA(A) receptors containing the alpha2 and/or alpha3 subunits. We show that their selective activation by the non-sedative ('alpha1-sparing') benzodiazepine-site ligand L-838,417 (ref. 13) is highly effective against inflammatory and neuropathic pain yet devoid of unwanted sedation, motor impairment and tolerance development. L-838,417 not only diminished the nociceptive input to the brain but also reduced the activity of brain areas related to the associative-emotional components of pain, as shown by functional magnetic resonance imaging in rats. These results provide a rational basis for the development of subtype-selective GABAergic drugs for the treatment of chronic pain, which is often refractory to classical analgesics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics / administration & dosage
  • Analgesics / metabolism
  • Analgesics / pharmacology
  • Analgesics / therapeutic use
  • Animals
  • Brain / drug effects
  • Brain / physiology
  • Capsaicin / pharmacology
  • Chronic Disease / drug therapy
  • Diazepam / administration & dosage
  • Diazepam / metabolism
  • Diazepam / pharmacology
  • Disease Models, Animal
  • Fluorobenzenes / metabolism
  • Fluorobenzenes / pharmacology
  • Formaldehyde
  • Ganglia, Spinal / cytology
  • Ganglia, Spinal / metabolism
  • Hot Temperature
  • Inflammation / chemically induced
  • Inflammation / drug therapy
  • Male
  • Mice
  • Neurons / drug effects
  • Neurons / metabolism
  • Organ Specificity
  • Pain / chemically induced
  • Pain / drug therapy*
  • Pain / metabolism*
  • Pain / prevention & control
  • Protein Isoforms / chemistry
  • Protein Isoforms / metabolism
  • Protein Subunits / chemistry
  • Protein Subunits / metabolism
  • Rats
  • Rats, Wistar
  • Receptors, GABA-A / chemistry
  • Receptors, GABA-A / genetics
  • Receptors, GABA-A / metabolism*
  • Spinal Cord / cytology
  • Spinal Cord / drug effects
  • Spinal Cord / metabolism*
  • Spinal Cord / physiopathology
  • Triazoles / metabolism
  • Triazoles / pharmacology

Substances

  • Analgesics
  • Fluorobenzenes
  • Protein Isoforms
  • Protein Subunits
  • Receptors, GABA-A
  • Triazoles
  • Formaldehyde
  • L 838,417
  • Diazepam
  • Capsaicin