Effects of sesquiterpenoids from "Oriental incenses" on acetic acid-induced writhing and D2 and 5-HT2A receptors in rat brain.

Six sesquiterpenoids, namely jinkoh-eremol, agarospirol, alpha- and beta-santalols, dehydrocostus lactone and costunolide, isolated from oriental incenses inhibited acetic acid-induced writhing in mice. The incidence of writhing produced by jinkoh-eremol, alpha-santalol and costunolide were revealed by administration of naloxone (mu-, kappa- and delta-antagonists). Inhibitory activities of alpha-santalol on opioid receptors were shown only by the delta antagonist, but not by the mu- and kappa-antagonists. The delta2-antagonist, but not the delta-antagonist, inhibited the activity of alpha santalol. The mechanism of inhibitory activity on the opioid receptor by alpha-santalol was different from that of morphine. Alpha-santalol was shown to be the most potent of the six as an antagonist of dopamine D2 and serotonine 5-HT2A receptor binding. The effect of alpha-santalol, was the same as that of chlorpromazine as an antipsychotic agent, although alpha-santalol was less potent than chlorpromazine.