Sympathetic α₃β₂-nAChRs mediate cerebral neurogenic nitrergic vasodilation in the swine

Am J Physiol Heart Circ Physiol. 2011 Aug;301(2):H344-54. doi: 10.1152/ajpheart.00172.2011. Epub 2011 May 2.

Abstract

The α(7)-nicotinic ACh receptor (α(7)-nAChR) on sympathetic neurons innervating basilar arteries of pigs crossed bred between Landrace and Yorkshire (LY) is known to mediate nicotine-induced, β-amyloid (Aβ)-sensitive nitrergic neurogenic vasodilation. Preliminary studies, however, demonstrated that nicotine-induced cerebral vasodilation in pigs crossbred among Landrace, Yorkshire, and Duroc (LYD) was insensitive to Aβ and α-bungarotoxin (α-BGTX). We investigated nAChR subtype on sympathetic neurons innervating LYD basilar arteries. Nicotine-induced relaxation of porcine isolated basilar arteries was examined by tissue bath myography, inward currents on nAChR-expressing oocytes by two-electrode voltage recording, and mRNA and protein expression in the superior cervical ganglion (SCG) and middle cervical ganglion (MCG) by reverse transcription PCR and Western blotting. Nicotine-induced basilar arterial relaxation was not affected by Aβ, α-BGTX, and α-conotoxin IMI (α(7)-nAChR antagonists), or α-conotoxin AuIB (α(3)β(4)-nAChR antagonist) but was inhibited by tropinone and tropane (α(3)-containing nAChR antagonists) and α-conotoxin MII (selective α(3)β(2)-nAChR antagonist). Nicotine-induced inward currents in α(3)β(2)-nAChR-expressing oocytes were inhibited by α-conotoxin MII but not by α-BGTX, Aβ, or α-conotoxin AuIB. mRNAs of α(3)-, α(7)-, β(2)-, and β(4)-subunits were expressed in both SCGs and MCGs with significantly higher mRNAs of α(3)-, β(2)-, and β(4)-subunits than that of α(7)-subunit. The Aβ-insensitive sympathetic α(3)β(2)-nAChR mediates nicotine-induced cerebral nitrergic neurogenic vasodilation in LYD pigs. The different finding from Aβ-sensitive α(7)-nAChR in basilar arteries of LY pigs may offer a partial explanation for different sensitivities of individuals to Aβ in causing diminished cerebral nitrergic vasodilation in diseases involving Aβ.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid beta-Peptides / metabolism
  • Animals
  • Basilar Artery / drug effects
  • Basilar Artery / innervation*
  • Blotting, Western
  • Dose-Response Relationship, Drug
  • Electric Stimulation
  • Female
  • Humans
  • Male
  • Membrane Potentials
  • Myography
  • Nicotinic Agonists / pharmacology
  • Nicotinic Antagonists / pharmacology
  • Nitrergic Neurons / drug effects
  • Nitrergic Neurons / metabolism*
  • Oocytes
  • Patch-Clamp Techniques
  • RNA, Messenger / metabolism
  • Receptors, Nicotinic / drug effects
  • Receptors, Nicotinic / genetics
  • Receptors, Nicotinic / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Superior Cervical Ganglion / drug effects
  • Superior Cervical Ganglion / metabolism*
  • Swine
  • Vasoconstrictor Agents / pharmacology
  • Vasodilation* / drug effects
  • Vasodilator Agents / pharmacology
  • Xenopus

Substances

  • Amyloid beta-Peptides
  • Nicotinic Agonists
  • Nicotinic Antagonists
  • RNA, Messenger
  • Receptors, Nicotinic
  • Vasoconstrictor Agents
  • Vasodilator Agents
  • nicotinic receptor alpha3beta2