Transfer of dopamine in the olfactory pathway following nasal administration in mice

Purpose. The aim of the study was to investigate whether dopamine is transferred along the olfactory pathway to the brain following nasal administration to mice. Methods. [H-3]-Dopamine was administered nasally or intravenously to female mice. Brain tissue samples were excised and the radioactive content was measured. The precise localisation of dopamine radioactivity in the brain was studied using autoradiography. The presence of dopamine or its metabolites in the olfactory bulb and mucosa was ascertained using thin layer chromatography (TLC). Results. After administration of [H-3]-dopamine into the right nostril, the amount of dopamine in the right bulb increased with time until, after 4 h, it was 27 times higher than in the left bulb. Among the other brain tissue samples, significantly higher amount of radioactivity was detected in the lateral olfactory tract. Radioactivity in the right olfactory bulb was shown by autoradiography to be selectively located in the peripheral layers 1 to 4 h after administration. Selective uptake of radioactivity was not seen in other regions of the brain. TLC data indicated that approximately 75% and 10% of the radioactivity in the olfactory bulb and mucosa, respectively, coeluted with dopamine. Conclusions. The results indicate that unchanged dopamine is transferred into the olfactory bulb following nasal administration of [H-3]-dopamine.