title: Black cohosh (Cimicifuga racemosa) relaxes the isolated rat thoracic aorta through endothelium-dependent and -independent mechanisms.
abstract: OBJECTIVE
  The rhizome of the Cimicifuga racemosa (commonly known as black cohosh) has been used in treatment of climacteric complaints for decades in North America and Europe. A number of studies investigated the estrogenic potential of black cohosh, but its effectiveness is still controversial. Recently, it was reported that the extract of black cohosh acted as an agonist at the serotonin (5-HT) receptor and 5-HT derivative was isolated out of the black cohosh extract. Because it is well known that the 5-HT elicited the various cardiovascular effects including vasorelaxation, we investigated the vasorelaxant effects of the extract of black cohosh and its possible mechanisms of action.
  
  
  METHODS
  The extract of black cohosh (BcEx) was examined for its vasorelaxant effects in isolated rat aorta. The aortic rings were equilibrated under resting tension and induced reproducible contraction in organ bath. The control contraction was produced by 300 nM NE, and then BcEx were added. In experiments where specific inhibitors were used, they were added 20 min before NE contraction.
  
  
  RESULTS
  BcEx elicited two phases of relaxation in rat aorta pre-contracted with norepinephrine. The first, a rapid relaxation, which occurred within seconds of BcEx administration, was eliminated by pretreatment with N(G)-nitro-l-arginine (l-NNA) or methylene blue. The endogenous NO synthase substrate l-Arg markedly reversed the action of l-NNA, indicating that BcEx elicited the vasorelaxant effect via the NO/cGMP pathway. The second, slowly developing relaxation was not affected by the endothelium denudation. BcEx-induced endothelium-independent vasorelaxation appears to involve the inhibition of calcium influx mediated by the opening of inward rectifier potassium channels.
  
  
  CONCLUSIONS
  BcEx elicits the vasorelaxant effect via endothelium-dependent and -independent mechanisms and may contribute to a better understanding of a potential link between the use of black cohosh and its beneficial effects on vascular health.
authors: Functional Food Technology Research Group, Korea Food Research Institute, Gyeonggi-do, Republic of Korea.
authors: Eun-Young
authors: EY
authors: Kim
authors: Young Joo
authors: YJ
authors: Lee
authors: Mee-Ra
authors: MR
authors: Rhyu
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000502:physiology; D031885:Cimicifuga / Q000737:chemistry*; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D010936:Plant Extracts; D014665:Vasodilator Agents