Nasal absorption of tetraethylammonium in rats

The in vivo and in situ nasal absorption of tetraethylammonium in rats was studied. Following nasal administration of tetraethylammonium (150 mumol/kg) to rats, there was a rapid increase in plasma concentration of tetraethylammonium followed by a slow increase. The absolute bioavailability of nasal tetraethylammonium administration was 79%. In rats, tetraethylammonium was shown to be more efficiently absorbed from nasal mucosa than from intestine. In in situ nasal perfusion experiments, the nasal absorption rate of tetraethylammonium was reduced by an increase in perfusion volume. The plot of absorption rate constant against 1/volume did not result in a straight line. In addition, there was a concentration-dependent decline in the absorption rate of tetraethylammonium with an increase in its initial concentration in the perfusion solution. Choline and 2,4-dinitrophenol significantly inhibited the nasal absorption of tetraethylammonium. These data may suggest the existence of a carrier-mediated transport process of tetraethylammonium in nasal mucosa of rats.