RESPONSES OF CULTURED RAT TRIGEMINAL GANGLION NEURONS TO BITTER TASTANTS

The initial steps in taste and olfaction result from the activation by chemical stimuli of taste receptor cells (TRCs) and olfactory recepto r neurons (ORNs). in parallel with these two pathways is the chemosens itive trigeminal pathway whose neurons terminate in the oral and nasal cavities and which are activated by many of the same chemical stimuli that activate TRCs and ORNs. in a recent single unit study we investi gated the responses of rat chorda tympani and glossopharnygeal neurons to a variety of bitter-tasting alkaloids, including nicotine, yohimbi ne, quinine,strychnine and caffeine; as well as capsaicin, the pungent ingredient in hot pepper. Here we apply many of these same compounds to cultured rat trigeminal ganglion (TG) neurons and measure changes i n intracellular calcium [Ca2+](i) to determine whether TS neurons will respond to these same compounds. Of the 89 neurons tested, 34% respon ded to 1 mM nicotine,7% to 1 mM caffeine, 5% to 1 mM denatonium benzoa te, 22% to 1 mM quinine hydrochloride, 18% to 1 mM strychnine and 55% to 1 mu M capsaicin. These data suggest that neurons from the TG respo nd to the same bitter-tasting chemical stimuli as do TRCs and are like ly to contribute information sent to the higher CNS regarding the perc eption of: bitter/irritating chemical stimuli.