3-Methylindole alters both olfactory and trigeminal nasal mucosal potentials in rats.

Data from human studies imply that vanillin is an olfactory stimulant, whereas CO2 activates intranasal trigeminal nociceptors. We examined the effects of the olfactotoxin 3-methylindole (3-MI) on nasal mucosal potentials evoked by vanillin and CO2 in rats. A single i.p. administration of 300 mg/kg 3-MI altered both olfactory and trigeminal mucosal responses. Relative to amplitude values determined in non-3-MI-injected rats, the response to vanillin was reduced to 6%, 7%, and 43%, and the response to CO2, recorded in the same rats, decreased to 25%, 38%, and 51% at 4, 8 and 16 days post-3-MI, respectively. The results suggest that 3-MI affects both olfactory and trigeminal elements within the nasal mucosa.