Fy. Chueh et al., HYPOTENSIVE AND BRADYCARDIAC EFFECTS OF DL-TETRAHYDROPALMATINE MEDIATED BY DECREASE IN HYPOTHALAMIC SEROTONIN RELEASE IN THE RAT, Japanese Journal of Pharmacology, 69(2), 1995, pp. 177-180
In anesthetized rats, intravenous administration of dl-tetrahydropalma
tine (dl-THP, 1-10 mg/kg) elicited proportional hypotension, bradycard
ia 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 a
nd bradycardia, while stimulation of 5-HT2 receptors with 1-(2,5-dimet
hoxy-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 sero
tonergic release process in the hypothalamus.