Fu-Yu Chueh (1), Ming-Tsuen Hsieh (1), Chieh-Fu Chen (2) and Mao-Tsun Lin (3,*)
(1) Institute of Chinese Pharmaceutical Sciences, China Medical College, Taichung, Taiwan
(2) National Research Institute of Chinese Medicine, Taipei Hsien, Taiwan
(3) Department of Physiology, National Cheng Kung University Medical College, Taiwan, Taiwan
Abstract: In anesthetized rats, intravenous administration of dl-tetrahydropalmatine (dl-THP, 1-10 mg/kg) elicited proportional hypotension, bradycardia and decreases in hypothalamic serotonin (5-HT) release (measured by carbon-fiber electrodes in combination with voltammetry). In addition, postsynaptic blockade of 5-HT2 receptors with cyproheptadine (2-5 mg/kg, i.v.) or ketanserin (2-5 mg/kg, i.v.) produced both hypotension and bradycardia, while stimulation of 5-HT2 receptors with 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (10-250 mg/kg, i.v.) produced both hypertension and tachycardia. The dl-THP-induced hypotension and bradycardia could be reversed by DOI treatment. The data indicate that dl-THP decreases both arterial pressure and heart rate through a serotonergic release process in the hypothalamus.
Keywords: dl-Tetrahydropalmatine, Blood pressure, Serotonin