title: Patterns of nicotinic receptor antagonism II: cardiovascular effects in rats.
abstract: BACKGROUND
  Tobacco cessation pharmacotherapies currently are limited to nicotine itself, the partial nicotine agonists varenicline and cytisine, and the antidepressant bupropion. Compared with agonists, nicotinic antagonists such as the noncompetitive, nonselective compound mecamylamine, and the competitive, α4β2-preferring antagonist dihydro-β-erythroidine (DHβE) may be a novel approach to the treatment of tobacco smoking as both are effective antagonists of nicotine's central effects. Considering nicotinic acetylcholine receptors mediate critical peripheral effects of acetylcholine, such as cardiovascular effects, it is important to study how nicotinic antagonists would alter the cardiovascular system and the cardiovascular changes induced by nicotine.
  
  
  METHODS
  The effects of several nicotinic agonists and antagonists on blood pressure and heart rate were measured in conscious, unrestrained rats following parenteral administration using a telemetry system.
  
  
  RESULTS
  Nicotine and other nicotinic receptor agonists (epibatidine, varenicline, and cytisine) produced similar increases in blood pressure, whereas their effects on heart rate were biphasic. The cardiovascular changes were attenuated by the nonselective nicotine antagonist, mecamylamine, but the peripherally restricted antagonist hexamethonium blocked only the agonist-induced changes in blood pressure. The α7-preferring antagonist, MLA, and the α4β2-preferring antagonist, DHβE, were much less effective in blocking the agonist-induced cardiovascular changes, indicating that nicotine's cardiovascular effects, are due to activation at autonomic ganglia involving nicotinic receptor subtypes other than α4, α7, or β2.
  
  
  CONCLUSIONS
  The data indicate that the cardiovascular effects of nicotine and nicotine-like agents are mediated through receptor mechanisms that are distinct from those that mediate the central effects of nicotine.
authors: Department of Pharmacology, University of Michigan, 1150 W Medical Center Drive, Ann Arbor, MI 48109-5632, USA.
authors: Emily M
authors: EM
authors: Jutkiewicz
authors: Kenner C
authors: KC
authors: Rice
authors: F Ivy
authors: FI
authors: Carroll
authors: James H
authors: JH
authors: Woods
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000502:physiology*
chemical_list: D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; C403531:nicotinic receptor alpha4beta2
keywords: Cardiovascular effects; Nicotine; Nicotinic agonists; Rats