Cardiovascular Effects of the Essential Oil of Croton nepetaefolius in Rats: Role of the Autonomic Nervous System

Abstract

Cardiovascular effects of intravenous (i.v.) treatment with the essential oil of Croton nepetaefolius (EOCN) were investigated in rats. Additionally, this study examined the importance of the autonomic nervous system in mediation of the EOCN-induced changes in mean aortic pressure (MAP) and heart rate (HR). In both pentobarbitone-anaesthetised and conscious rats, i.v. bolus injections of EOCN (1 to 50 mg/kg) elicited dose-dependent decreases in MAP and HR. Both decreases were of the same order of magnitude or duration, irrespective of whether the animal was under general anaesthesia. Pretreatment of anaesthetised rats with bilateral vagotomy reduced the magnitude of EOCN-induced bradycardia without affecting hypotension. Likewise, i.v. pretreatment of conscious rats with either methylatropine (1 mg/kg) or hexamethonium (30 mg/kg) significantly decreased the bradycardic effects of EOCN by the same order of magnitude. Neither compound influenced the hypotensive effects elicited by EOCN. This is the first physiological evidence that i.v. treatment with EOCN in either anaesthetised or conscious rats elicits hypotension and bradycardia. EOCN-induced bradycardia appears dependent upon the presence of an intact and functional parasympathetic nerve drive to the heart. However, EOCN-induced hypotension appears independent of the presence of an operational sympathetic nervous system. This suggests that EOCN may be a direct vasorelaxant agent.

Cardiovascular effects of 1,8-cineole, a terpenoid oxide present in many plant essential oils, in normotensive rats

“…Baseline MAP and HR values of anesthetized or conscious, freely moving, normotensive rats were of the same order of magnitude as those previously reported using the same preparation (Lahlou et al 1999(Lahlou et al , 2001). In both groups, i.v.…”

“…These findings with i.v. hexamethonium are in line with those previously reported in normotensive rats treated with EOCN (Lahlou et al 1999) and suggest that the hypotensive response to 1,8-cineole may be due to an active vascular relaxation rather than to a withdrawal of sympathetic tone. Such a hypothesis is corroborated by the present finding that in rat isolated aorta preparations, 1,8-cineole was able to inhibit the potassiuminduced contraction in a concentration-dependent manner.…”

“…Previous studies showed that this vehicle had no effects on either baseline MAP or HR during a period of 20 min (Lahlou et al 1999(Lahlou et al , 2000(Lahlou et al , 2001. The perfusion medium used was fresh modified Tyrode's solution of the following composition: 136 mM NaCl, 5 mM KCl, 0.98 mM MgCl 2 , 2 mM CaCl 2 , 0.36 mM NaH 2 PO 4 , 11.9 mM NaHCO 3 , and 5.5 mM glucose.…”

“…Previous studies from our laboratory showed that i.v. treatment with either EOCN or EOAZ induced dose-dependent decreases in mean aortic pressure (MAP) in either anesthetized or conscious normotensive rats (Lahlou et al 1999(Lahlou et al , 2002. Both in vivo and in vitro data suggested that the hypotensive responses to EOCN (Lahlou et al 2000) and EOAZ (Galindo et al 2001;Lahlou et al 2002) result from their vasodilatory action directly upon vascular smooth muscle rather than from withdrawal of sympathetic tone.…”

Antinociceptive effects of the essential oil of Croton nepetaefolius on mice

“…Available studies have dealt only with the chemical composition of the essential oil of C. nepetaefolius (EOCn) and its pharmacological effects on intestinal, respiratory and vascular smooth muscle and on arterial pressure (2)(3)(4)(5)(6). While EOCn is present in relatively large quantities in the leaves of the plant (1% yield) (7), pharmacological investigations have shown that it has potent antispasmodic activity, consistent with its use in folk medicine.…”