Animal experiment:

Mice[1]Male ICR mice are pretreated with Reserpine (5 mg/kg, i.p.) 3 h before the start of the experiments. Rhynchophylline (RHY), Corynoxeine (COX), Isocorynoxeine (ICOX, 10 and 30 mg/kg) or vehicle is injected i.p. 30 min before 5-MeO-DMT[1].

Isocorynoxeine, an isorhynchophylline-related alkaloid, exhibits a dose-dependent inhibition of 5-HT2A receptor-mediated current response with an IC50 of 72.4 μM.

Isocorynoxeine inhibits 5-HT2A receptor-mediated 5-HT currents. Isocorynoxeine prefer to interact with 5-HT2A receptors rather than with 5-HT2C receptors in the brain.Isocorynoxeine exhibits less potent inhibitory activity (with IC50 values of >100 μM) against the 5-HT2C receptor-mediated response than the 5-HT2A receptor-mediated response in oocytes. Isocorynoxeine dose-dependently and competitively inhibits 5-HT-evoked currents in Xenopus oocytes expressing 5-HT2A receptors, but has less of a suppressive effect on those in oocytes expressing 5-HT2C receptors[1].

The effects of Rhynchophylline, Corynoxeine, and Isocorynoxeine, isorhynchophylline-related alkaloids present are tested in Uncaria species, on 5-MeO-DMT-induced head-twitch behaviour in reserpinized mice. Neither Rhynchophylline [H=1.369, P=0.504] nor Corynoxeine [H=0.242, P=0.886] affects the behaviour, while Isocorynoxeine significantly attenuates it at 30 mg/kg (i.p.) [H=7.582, P<0.01][1].

References:
[1]. Matsumoto K, et al. Suppressive effects of isorhynchophylline on 5-HT2A receptor function in the brain: behavioural and electrophysiological studies. Eur J Pharmacol. 2005 Jul 11;517(3):191-9.