Lahlou S, Leal-Cardoso J H, Magalhães P J
Departamento de Fisiologia e Farmacologia, Universidade Federal de Pernambuco, Recife-PE, Brasil.
Planta Med. 2000 Mar;66(2):138-43. doi: 10.1055/s-2000-11133.
Experiments tested the hypothesis that hypotensive effects of intravenous (i.v.) treatment with the essential oil of Croton nepetaefolius (EOCN) result from its vasodilatory effects directly upon vascular smooth muscle. In both deoxycorticosterone-acetate (DOCA)-salt hypertensive and uninephrectomised control, conscious rats, i.v. bolus injections of EOCN (1 to 50 mg/kg) decreased mean aortic pressure (MAP) and heart rate (HR) in a dose-related manner. Treatment with DOCA-salt significantly enhanced EOCN-induced decreases in MAP without affecting bradycardia. Likewise, both maximal percent and absolute decreases in MAP elicited by i.v. hexamethonium (30 mg/kg), a ganglion blocker, were significantly greater in DOCA-salt hypertensive than in control rats. In DOCA-salt hypertensive rats, i.v. pretreatment with hexamethonium (30 mg/kg) reduced the bradycardia elicited by EOCN (50 mg/kg) without affecting the enhancement of EOCN-induced hypotension. In isolated thoracic aorta preparations from DOCA-salt hypertensive rats, EOCN (1-300 micrograms/ml) induced a concentration-dependent reduction of phenylephrine-induced contraction. Arteries from DOCA rats showed increased sensitivity to EOCN, as evidenced by the significant decrease in the IC50 for EOCN-induced reduction of phenylephrine-induced contraction (16.4 +/- 3.6 vs. 112.9 +/- 23.4 micrograms/ml in uninephrectomized controls). These results show that i.v. treatment with EOCN dose-dependently decreases blood pressure in conscious DOCA-salt hypertensive rats, and this action is enhanced when compared with uninephrectomized controls. This enhancement appears to be related mainly to an increase in EOCN-induced vascular smooth muscle relaxation rather than to enhanced sympathetic nervous system activity in this hypertensive model. Thus, the hypothesis that EOCN may be a direct vasorelaxant agent is supported by the results of the present study.
巴豆叶香精油静脉注射（i.v.）的降压作用源于其对血管平滑肌的直接舒张作用。在醋酸脱氧皮质酮（DOCA）-盐高血压大鼠和单侧肾切除对照清醒大鼠中，静脉推注巴豆叶香精油（EOCN，1至50mg/kg）均以剂量相关方式降低平均主动脉压（MAP）和心率（HR）。DOCA-盐处理显著增强了EOCN诱导的MAP降低，而不影响心动过缓。同样，静脉注射神经节阻滞剂六甲铵（30mg/kg）引起的MAP最大百分比和绝对降低在DOCA-盐高血压大鼠中比对照大鼠显著更大。在DOCA-盐高血压大鼠中，静脉注射六甲铵（30mg/kg）预处理可降低EOCN（50mg/kg）引起的心动过缓，而不影响EOCN诱导的低血压增强。在DOCA-盐高血压大鼠的离体胸主动脉制备物中，EOCN（1-300μg/ml）诱导去氧肾上腺素诱导的收缩呈浓度依赖性降低。DOCA大鼠的动脉对EOCN的敏感性增加，这通过EOCN诱导的去氧肾上腺素诱导收缩降低的IC50显著降低得到证明（单侧肾切除对照中为112.9±23.4μg/ml，而DOCA大鼠中为16.4±3.6μg/ml）。这些结果表明，静脉注射EOCN可使清醒的DOCA-盐高血压大鼠血压呈剂量依赖性降低，与单侧肾切除对照相比，这种作用增强。这种增强似乎主要与EOCN诱导的血管平滑肌舒张增加有关，而不是与该高血压模型中交感神经系统活性增强有关。因此，本研究结果支持EOCN可能是一种直接血管舒张剂的假设。
