The function of several types of ligand-gated ion channels is changed by cannabinoids—as a rule, these effects are not mediated by CB1 receptors. In isolated rat nodose ganglion neurons, cannabinoids inhibited serotonin-3 (5-HT3) receptor-mediated currents (Fan 1995). This observation was verified and extended in a recent study. In HEK293 cells expressing the human 5-HT3A receptor, several cannabinoids inhibited the 5-HT-evoked current (Barann et al. 2002). CB1 receptors could not be involved in this effect, since HEK293 cells do not express CB1 receptors.
The function of AMPA-type glutamate receptors (Akinshola et al. 1999) and nicotinic acetylcholine receptors (Oz et al. 2003), expressed in oocytes, was inhibited by anandamide. These effects are, again, CB1 and CB2 receptor-independent.
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