α6ß2* and α4ß2* nicotinic receptors both regulate dopamine signaling with increased nigrostriatal damage: relevance to Parkinson's disease

Mol Pharmacol. 2010 Nov;78(5):971-80. doi: 10.1124/mol.110.067561. Epub 2010 Aug 23.

Abstract

Nicotinic receptors (nAChRs) are important modulators of dopaminergic transmission in striatum, a region critical to Parkinson's disease. The nAChRs mainly involved are the α6β2* and α4β2* subtypes. Lesion studies show that the α6β2* receptor is decreased to a much greater extent with nigrostriatal damage than the α4β2* subtype raising the question whether this latter nAChR population is more important with increased nigrostriatal damage. To address this, we investigated the effect of varying nigrostriatal damage on α6β2* and α4β2* receptor-modulated dopamine signaling using cyclic voltammetry. This approach offers the advantage that changes in dopamine release can be observed under different neuronal firing conditions. Total single-pulse-evoked dopamine release decreased in direct proportion to declines in the dopamine transporter and dopamine uptake. We next used α-conotoxinMII and mecamylamine to understand the role of the α4β2* and α6β2* subtypes in release. Single-pulse-stimulated α6β2* and α4β2* receptor dopamine release decreased to a similar extent with increasing nigrostriatal damage, indicating that both subtypes contribute to the control of dopaminergic transmission with lesioning. Total burst-stimulated dopamine release also decreased proportionately with nigrostriatal damage. However, the role of the α4β2* and α6β2* nAChRs varied with different degrees of lesioning, suggesting that the two subtypes play a unique function with burst firing, with a somewhat more prominent and possibly more selective role for the α6β2* subtype. These data have important therapeutic implications because they suggest that drugs directed to both α4β2* and α6β2* nAChRs may be useful in the treatment of neurological disorders such as Parkinson's disease.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials
  • Animals
  • Autoradiography
  • Binding Sites
  • Corpus Striatum / metabolism*
  • Corpus Striatum / pathology
  • Corpus Striatum / physiopathology
  • Dopamine / metabolism*
  • Dopamine Plasma Membrane Transport Proteins / metabolism
  • Male
  • Neurons / pathology
  • Neurons / physiology
  • Nicotinic Antagonists / pharmacology
  • Oxidopamine
  • Parkinson Disease / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Nicotinic / physiology*
  • Signal Transduction
  • Substantia Nigra / metabolism*
  • Substantia Nigra / pathology
  • Substantia Nigra / physiopathology

Substances

  • Dopamine Plasma Membrane Transport Proteins
  • Nicotinic Antagonists
  • Receptors, Nicotinic
  • alpha6beta2 nicotinic acetylcholine receptor
  • nicotinic receptor alpha4beta2
  • Oxidopamine
  • Dopamine