Intranasal delivery of insulin via the olfactory nerve pathway

Objectives Intranasal delivery has been shown to target peptide therapeutics to the central nervous system (CNS) of animal models and induce specific neurological responses. In an investigation into the pathways by which intranasal administration delivers insulin to the CNS, this study has focused on the direct delivery of insulin from the olfactory mucosa to the olfactory bulbs via the olfactory nerve pathway. Methods Nasal and olfactory tissues of mice were imaged with fluorescent and electron microscopy 30 min following intranasal administration. Key findings Macroscopic analysis confirmed delivery to the anterior regions of the olfactory bulbs. Confocal microscopy captured delivery along the olfactory nerve bundles exiting the nasal mucosa, traversing the cribriform plate and entering the bulbs. With electron microscopy, insulin was found within cells of the olfactory nerve layer and glomerular layer of the olfactory bulbs. Conclusions These results demonstrated that intranasal administration of labelled insulin targeted the CNS through the olfactory nerve pathway in mice.