Hypotensive and bradycardic effects of dl-tetrahydropalmatine mediated by decrease in hypothalamic serotonin release in the rat.
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.
Chueh
F Y
FY
Institute of Chinese Pharmaceutical Sciences, China Medical College, Taichung, Taiwan.
Hsieh
M T
MT
Chen
C F
CF
Lin
M T
MT
D018663:Adrenergic Agents / Q000494:pharmacology*; D000818:Animals; D001600:Berberine Alkaloids / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D001919:Bradycardia / Q000378:metabolism*; D007022:Hypotension / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D013997:Time Factors
D018663:Adrenergic Agents; D001600:Berberine Alkaloids; D012701:Serotonin; C014215:tetrahydropalmatine