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Hypotensive and Bradycardic Effects of dl-Tetrahydropalmatine Mediated by Decrease in Hypothalamic Serotonin Release in the Rat

1995; Japanese Pharmacological Society; Volume: 69; Issue: 2 Linguagem: Inglês

10.1254/jjp.69.177

1347-3506

Fu‐Yu Chueh, Ming‐Tsuen Hsieh, Chieh‐Fu Chen, Mao-Tsun Lin,

Receptor Mechanisms and Signaling

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.