The involvement of pertussis toxin-sensitive G proteins in the post receptor mechanism of central I1-imidazoline receptors

Br J Pharmacol. 1997 Apr;120(8):1575-81. doi: 10.1038/sj.bjp.0701090.

Abstract

1. To elucidate the possible involvement of pertussis toxin (PTX)-sensitive G proteins in the post receptor mechanism of alpha 2-adrenoceptors and imidazoline receptors, we examined the effect of pretreatment of the central nervous system with PTX on the antidysrhythmic effect of dexmedetomidine, a selective alpha 2-adrenoceptor agonist, and rilmenidine, a selective I1-imidazoline receptor agonist on halothane-adrenaline dysrhythmias in rats. 2. Dexmedetomidine (0, 1.0, 2.0, 5.0 micrograms kg-1 min-1.i.v.) and rilmenidine (0, 1.0, 3.0, 10, 20 micrograms kg-1, i.v.) prevented the genesis of halothane-adrenaline dysrhythmias in a dose-dependent fashion. Both idazoxan (10, 20 micrograms kg-1, intracerebroventricularly (i.c.v.)), an alpha 2-adrenoceptor antagonist with high affinity for imidazoline receptors, and rauwolscine, (40 micrograms kg-1, i.c.v.), an alpha 2-adrenoceptor antagonist with low affinity for imidazoline receptors inhibited the action of dexmedetomidine (5.0 micrograms kg-1, min-1, i.v.), but the inhibitory potency of idazoxan was much greater than that of rauwolscine. While the pretreatment with PTX (0.1, 0.5, 1.0 micrograms kg-1, i.c.v.) did not change the dysrhythmogenecity of adrenaline, this treatment completely blocked the antidysrhythmic property of rilmenidine (20 micrograms kg-1, i.v.) as well as dexmedetomidine (5.0 micrograms kg-1 min-1, i.v.). 3. It is suggested that central I1-imidazoline receptors as well as alpha 2-adrenoceptors may be functionally coupled to PTX-sensitive G proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic alpha-2 Receptor Agonists
  • Adrenergic alpha-Agonists / pharmacology
  • Animals
  • GTP-Binding Proteins / physiology*
  • Imidazoles / pharmacology
  • Imidazoline Receptors
  • Male
  • Medetomidine
  • Oxazoles / pharmacology
  • Pertussis Toxin*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Adrenergic, alpha-2 / metabolism
  • Receptors, Adrenergic, alpha-2 / physiology
  • Receptors, Drug / drug effects
  • Receptors, Drug / metabolism
  • Receptors, Drug / physiology*
  • Rilmenidine
  • Signal Transduction
  • Virulence Factors, Bordetella / pharmacology*

Substances

  • Adrenergic alpha-2 Receptor Agonists
  • Adrenergic alpha-Agonists
  • Imidazoles
  • Imidazoline Receptors
  • Oxazoles
  • Receptors, Adrenergic, alpha-2
  • Receptors, Drug
  • Virulence Factors, Bordetella
  • Pertussis Toxin
  • GTP-Binding Proteins
  • Medetomidine
  • Rilmenidine