Autonomic Nervous System Mediates the Hypotensive Effects of Aqueous and Residual Methanolic Extracts of Syzygium polyanthum (Wight)‎ Walp. var. polyanthum Leaves in Anaesthetized Rats

Abstract EN

Syzygium polyanthum (Wight) Walp.

var.

polyanthum leaves are consumed as a traditional Malay treatment of hypertension.

This study investigates hypotensive potential of aqueous (AESP) and residual methanolic (met-AESP) extracts of S.

polyanthum leaves and possible involvement of autonomic receptors.

AESP and met-AESP (20 to 100 mg/kg) were intravenously administered into anaesthetized Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats.

Blood pressure and heart were monitored for 20 min.

AESP and met-AESP induced significant dose-dependent hypotension, but only 100 mg/kg AESP caused mild bradycardia (n=5).

AESP-induced hypotension was more potent than that of met-AESP in WKY.

AESP has a faster onset time than that of met-AESP in both WKY and SHR.

However, met-AESP-induced hypotension was more sustained than that of AESP in SHR.

Blockages of autonomic ganglion and α-adrenergic receptors using hexamethonium and phentolamine (n=5 for each group) partially attenuated AESP-induced hypotension, suggesting involvement of α-adrenergic receptors.

Blockages of autonomic ganglion, β-adrenergic, cholinergic receptors, and nitric oxide production using hexamethonium, propranolol, atropine, and N-ω-nitro-l arginine methyl ester (L-NAME) (n=5 for each group) partially attenuated met-AESP-induced hypotension, suggesting involvement of β-adrenergic and cholinergic receptors via nitric oxide production.