RESUMO
Cecropia pachystachya Mart. is popularly called "ambay" and extensively used in herbal medicine of South America for cough and asthma. In Argentina it grows in neotropical rainforest (Ntr C.p.) and in a temperate region (Tp C.p.). In a previous work we showed their hypotensive properties with different potency and toxicity, and now we studied the Tp C.p. effects in isolated heart from rats and central effects of both plants on the open-field test for mice. Tp C.p. produced a positive inotropic effect on isolated rat hearts, which was not affected by 1 microM propranolol, suggesting that it is not due to a beta-adrenergic effect. In contrast, it was prevented by pretreatment with high [K](o) media, which stimulates the Na,K-ATPase pump, suggesting an inhibition of the pump by "ambay", as digital do. In the open-field test, both Ntr C.p. and Tp C.p. similarly decreased the spontaneous locomotion and exploratory behavior of mice at doses between 180 and 600 mg/kg. Ntr C.p. potentiated the effect of 3 mg/kg diazepam to one similar to 10 mg/kg diazepam, but was not antagonized by 0.5 mg/kg flumazenil. Amphetamine at 5 mg/kg prevented the sedative effect of Ntr C.p. Chromatographic analysis showed that both plants have a qualitatively similar fingerprint but quantitatively differed in at least three components. Although the purpose was not to identify them, both plants have at least 10 compounds. Two of them were in higher amount in Tp C.p. than in Ntr C.p., and then, they could be responsible for the cardiovascular toxicity of Tp C.p. In conclusion, the results suggest that ambay has cardiotonic and sedative properties. The sedative effect could be useful in cough treatment. The extract resulted additive to benzodiazepines but it did not bind to the same site on GABA-A receptor, and it was interfered by the dopamine release produced with amphetamine.
Assuntos
Cardiotônicos/farmacologia , Fármacos Cardiovasculares/farmacologia , Cecropia/química , Coração/efeitos dos fármacos , Hipnóticos e Sedativos/farmacologia , Extratos Vegetais/farmacologia , Anfetamina/farmacologia , Animais , Argentina , Benzodiazepinas/química , Fármacos Cardiovasculares/administração & dosagem , Cromatografia Líquida de Alta Pressão , Diazepam/farmacologia , Dopamina/metabolismo , Feminino , Flumazenil/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Masculino , Camundongos , Extratos Vegetais/administração & dosagem , Ratos , Ratos Wistar , Receptores de GABA-A/metabolismoRESUMO
Cecropia pachystachya is used in South America for relieving cough and asthma. In Argentina it is known as "ambay" and grows in the neotropical forests (Ntr C.p.) and in temperate hilly regions (Tp C.p.). To evaluate their cardiovascular profile, the effect of extracts obtained from plants growing in the neotropical region as well as in temperate areas were compared by i.v. administration in normotensive rats. The following parameters were measured: blood pressure (BP) and heart rate (HR). The hypotensive effect was stronger for Ntr C.p., which aqueous extract decreased BP at doses between 90 and 300 mg lyophilised/kg until 46.2 +/- 12% of basal. The extract of Tp C.p. reduced BP to 86.1 +/- 11% of basal (p < 0.05 respect to Ntr C.p.) at 180 mg/kg, but increased HR at 90 and 180 mg/kg (until 133.6 +/- 10.8% of basal, p < 0.05) and produced death by respiratory paralysis at 320 mg/kg (about 3g dry leaves/kg). The hypotensive effects, but not the chronotropic ones, were attenuated by pretreatment with reserpine (5 mg/kg). The plant extracts had not diuretic activity by oral administration in conscious rats, nor produced vasodilation of perfused hindquarters arterial bed precontracted with high-[K] or 100 microM phenylephrine. The results suggest that neotropical ambay is more hypotensive than the one from the temperate hilly region. When it reaches plasma, it could produce hypotension (by central blockade of sympathic innervation of vessels) and tachycardia (by central cholinergic inhibition of heart), although it happens at doses higher than the oral ethnotherapeutic (about 340 mg dried leaves/kg).