Pharmacological Evidence of α₂-Adrenergic Receptors in the Hypotensive Effect ofPlatonia insignisMart.

Abstract

Platonia insignis Mart. (Clusiaceae) is a medicinal plant from the Brazilian Amazon region. The present study evaluated the biological potential of the ethanol extract (Pi-EtOH) and ethyl acetate fraction (Pi-EtOAc) of the P. insignis fruit shells on the cardiovascular system of rats. Pi-EtOH or Pi-EtOAc (12.5, 25, and 50 mg/kg) was administered intravenously in normotensive rats (260-300 g), and the mean arterial pressure and the heart rate were monitored. The Pi-EtOH induced hypotension ( -11.56 -0.89, -7.43 -0.85, and -17.56 -1.97 mmHg) followed by bradycardia in two highest doses ( -8.89 -3.62 and -15.79 -1.83 beats/min) and Pi-EtOAc, at the same doses, induced hypotension ( -11.2 -1.03, -14.48 -1.13, -29.89 -2.67 mmHg) more intensively, followed by tachycardia at the dose 12.5 and 25 mg/kg (15.64 -2.06, 19.31 -1.92 beats/min) and bradycardia at a dose of 50 mg/kg ( -9.98 -7.33 beats/min). The hypotensive response from Pi-EtOAc was not attenuated when used in the pretreatment with L-NAME, verapamil, propranolol, and hexamethonium. However, when using yohimbine, the hypotensive effect was inhibited ( -4.42 -1.28 (P < .05), -3.29 -0.99 (P < .05), 2.06 -1.18 mmHg (P < .05); Student's t-test). Hence, the Pi-EtOAc seems to act similarly to the a2-adrenergic agonist in this hypotensive effect.

Antihypertensive Effects of Brazilian Fruits

“…The potentiation of the effect by the co-administration with L-NAME was observed. Moreover, the hypotensive effect was completely abolished by the administration of yohimbine, which indicates that the primary mechanism by which the extract promotes hypotension is via the α-adrenergic receptor (Mendes et al, 2014).…”

“…A study performed by Mendes et al (2014) evaluated the acute hypotensive effects of ethanol extract and ethyl acetate at different doses (12.5, 25 and 50 mg/kg) from Platonia insignis fruit peel in normotensive animals. The study only demonstrated a significant reduction in the mean arterial pressure at doses of 25 and 50 mg/kg in the ethyl acetate fraction.…”

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