Nicotinic acetylcholine receptors containing alpha 7 subunits on rat cortical neurons do not undergo long-lasting inactivation even when up-regulated by chronic nicotine exposure

J Neurochem. 2001 Sep;78(6):1367-78. doi: 10.1046/j.1471-4159.2001.00526.x.


Chronic exposure to (-)nicotine has been widely reported to up-regulate nicotinic acetylcholine receptors on neurons and induce long-term inactivation as a possible cause. Nicotinic receptors containing alpha 7 subunits are among the most abundant in brain and influence diverse cellular events. Whole-cell patch clamp recording from embryonic rat cortical neurons in culture was used to identify responses from alpha 7-containing receptors. Immunochemical staining for glutamic acid decarboxylase (GAD) indicated that both GABAergic and non-GABAergic neurons expressed the receptors. Exposure to micromolar concentrations of nicotine for 1-4 days caused up-regulation of the receptors as measured by [alpha-(125)I]-bungarotoxin binding. Carbachol produced the same up-regulation, and cell counts demonstrated that neuronal survival was unchanged. The up-regulation was accompanied by an increased whole-cell response; no evidence was found for long-lasting inactivation. Autonomic alpha 7-containing receptors also avoided long-lasting inactivation, even though the receptors were down-regulated by nicotine. Blocking protein synthesis or protein glycosylation prevented receptor up-regulation on cortical neurons, suggesting that new synthesis was required. No evidence was found for a pre-existing intracellular pool that supplied receptors to the surface. The results indicate that alpha 7-containing receptors differ from other receptor subtypes in their regulation by nicotine and demonstrate further that long-lasting inactivation is not an obligatory requirement for up-regulation in this case.

Publication types

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

MeSH terms

  • Animals
  • Cells, Cultured
  • Cerebral Cortex / cytology
  • Cerebral Cortex / drug effects
  • Cerebral Cortex / metabolism*
  • Nerve Tissue Proteins / biosynthesis
  • Neurons / drug effects
  • Neurons / metabolism*
  • Nicotine / pharmacology*
  • Nicotinic Agonists / pharmacology*
  • Protein Isoforms / metabolism
  • Rats
  • Receptors, Nicotinic / chemistry
  • Receptors, Nicotinic / drug effects*
  • Receptors, Nicotinic / metabolism*
  • Time Factors
  • Up-Regulation*


  • Nerve Tissue Proteins
  • Nicotinic Agonists
  • Protein Isoforms
  • Receptors, Nicotinic
  • Nicotine