Cardiovascular effects of eugenol, a phenolic compound present in many plant essential oils, in normotensive rats.
Cardiovascular effects of intravenous (i.v.) treatment with eugenol (Eug), a natural pungent present in many plant essential oils, were investigated in normotensive rats. In either anesthetized or conscious rats, i.v. bolus injections of Eug (1 to 10 mg/kg) elicited immediate and dose-dependent hypotension and bradycardia. Magnitude of Eug-induced hypotension was similar in both groups. Pretreatment of anesthetized rats with bilateral vagotomy almost abolished the bradycardic responses to Eug without affecting the hypotension. Likewise, i.v. pretreatment of conscious rats with methylatropine (1 mg/kg) or hexamethonium (30 mg/kg) significantly reduced the Eug-induced bradycardia without affecting the hypotension. However, i.v. pretreatment with the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl (L-NAME, 20 mg/kg), affected neither the hypotension nor the bradycardia elicited by Eug. In rat mesenteric bed preparations precontracted with potassium (60 mM), Eug (0.1-2 mM) induced a reversible and concentration-dependent vasodilator effect, which remained unaffected by atropine (1 microM). These results show that i.v. treatment of rats with Eug induces dose-dependent hypotension and bradycardia, which occurred independently. The bradycardia appears dependent upon the presence of an intact and functional parasympathetic nerve drive to the heart while the hypotension is due to an active vascular relaxation rather than withdrawal of sympathetic tone. Released nitric oxide from vascular endothelial cells seems to be not involved in the mediation of Eug-induced hypotension.
Lahlou
Saad
S
Department of Physiology and Pharmacology, Federal University of Pernambuco, Recife, Brazil. lahlou@ufpe.br
Interaminense
Leylliane Fátima Leal
LF
Magalhães
Pedro Jorge Caldas
PJ
Leal-Cardoso
José Henrique
JH
Duarte
Gloria Pinto
GP
D000818:Animals; D001341:Autonomic Nervous System / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D001919:Bradycardia / Q000139:chemically induced*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005054:Eugenol / Q000008:administration & dosage / Q000633:toxicity*; D006339:Heart Rate / Q000187:drug effects; D007022:Hypotension / Q000139:chemically induced*; D007275:Injections, Intravenous; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010938:Plant Oils / Q000008:administration & dosage / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar
D004791:Enzyme Inhibitors; D010938:Plant Oils; D005054:Eugenol; D019331:NG-Nitroarginine Methyl Ester