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Evidence-Based Complementary and Alternative Medicine
Volume 2013, Article ID 716532, 16 pages
http://dx.doi.org/10.1155/2013/716532
Research Article

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

1School of Health Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
2Department of Basic Medical Sciences, Kulliyyah of Dentistry, Kuantan Campus, International Islamic University Malaysia, Jalan Sultan Ahmad Shah, Bandar Indera Mahkota, 25200 Kuantan, Pahang, Malaysia
3Department of Physiology, School of Medical Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
4Department of Pharmacology, School of Medical Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia

Received 17 April 2013; Revised 22 October 2013; Accepted 30 October 2013

Academic Editor: Keji Chen

Copyright © 2013 A. Ismail et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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