A highly potent and selective H3 agonist relaxes rabbit middle cerebral artery, in vitro

Eur J Pharmacol. 1988 Jun 10;150(3):393-6. doi: 10.1016/0014-2999(88)90026-x.


An H3-agonist, R alpha methylhistamine strongly relaxed isolated and perfused rabbit middle cerebral artery precontracted with K+. This vasodilatation was not antagonized by either mepyramine or cimetidine but was competitively antagonized by an H3-antagonist, a mixture of impromidine and cimetidine. Histamine activated the H3-sites in this artery since its concentration-response curve (obtained with mepyramine and cimetidine) was parallel to that of R alpha methylhistamine. Our data indicate that H3-sites could exist in the rabbit cerebral artery.

MeSH terms

  • Animals
  • Cerebral Arteries / drug effects
  • Cimetidine / pharmacology
  • Histamine / pharmacology
  • Imidazoles / pharmacology
  • Impromidine
  • In Vitro Techniques
  • Male
  • Methylhistamines / pharmacology*
  • Muscle Relaxation / drug effects
  • Muscle, Smooth, Vascular / drug effects*
  • Potassium / pharmacology
  • Pyrilamine / pharmacology
  • Rabbits
  • Receptors, Histamine / drug effects*


  • Imidazoles
  • Methylhistamines
  • Receptors, Histamine
  • Cimetidine
  • Histamine
  • Impromidine
  • Pyrilamine
  • Potassium
  • N-methylhistamine