Short- and long-term effects of reserpine on rat cardiac beta-adrenoceptors

1. In order to explore the mechanism of reserpine-induced supersensitivity, we examined the effects of various doses of reserpine (R) on rat cardiac beta-adrenoceptors (beta AR). 2. 24 hr after a single administration of R (1 mg/kg, i.p.) beta AR were up-regulated, while with higher doses (2.5-5 mg/kg) beta AR density was not changed but beta AR coupling, evaluated by the proportion of high-affinity agonist binding states, was impaired. 3. Long-term effects of R (2.5 mg/kg/day, 2 days) included beta AR down-regulation and uncoupling 24 hr treatment (day 1), followed by up-regulation at day 7, while all parameters were similar to controls at day 14. 4. It appears that R induces either an increase or a decrease of cardiac beta AR density and coupling, dependent on the dose and the time at which beta AR are measured after treatment.