Hypotensive action of l-stepholidine in relation of dopamine receptors

Spontaneously hypertensive (SH) and 2 kidney 1 clip hypertensive (2k1cH) rats were treated with ig l-stepholidine (SPD) 200 mg/(kg.d). Two wk after medication, the average blood pressure (BP) of SH and 2k1cH were 21.3 +/- 3.8 and 25.5 +/- 3.8 kPa lower than their controls respectively. The concentration of serum prolactin in treated SH and 2klcH decreased by 48% and 54%, respectively with its decrease of BP. The levels of plasma norepinephrine and epinephrine were increased and the excretion of urinary sodium was reduced or not changed. Since the level of prolactin is a biochemical index of central dopamine receptor (D-2) activity, so these results suggest that the regulation of central dopamine receptors may take part in hypotensive action of ig SPD and the peripheral dopamine receptors are neither agonistic to SPD nor involved in hypotensive action.