Benzodiazepine agonist-type activity of raubasine, a rauwolfia serpentina alkaloid

Raubasine produced a dose-related inhibition of specific [3H]flunitrazepam binding to rat brain membranes. Scatchard analyses revealed a significant increase in the affinity constant but no change in the number of binding sites, suggesting that raubasine acts as a competitive inhibitor. Raubasine also inhibited the in vivo binding of [3H]flunitrazepam to mouse brain sites. Behavioral studies showed raubasine to possess anticonvulsant properties against pentylenetetrazol- and bicuculline-induced convulsions in mice. These effects were inhibited by the benzodiazepine antagonist, Ro 15-1788. The results suggest that raubasine interacts directly at benzodiazepine sites with a benzodiazepine agonist-type activity.