The effects of intranasal infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) upon catecholamine concentrations within olfactory bulbs and corpus striatum of male mice

Male C57/B1 mice received bilateral intranasal infusions of saline, MPTP or an intraperitoneal injection of MPTP. Infusions were performed using a peristaltic pump at a setting of 100 mu l/min. The MPTP, diluted in saline at concentrations of 2 mg/ml, was infused over 15 (0.1 mg) or 30 (0.2 mg) s, while the saline (control) infusions were of 30 s duration. In a separate group of mice, MPTP was injected via the intraperitoneal route at a dose equivalent to that of the 30-s intranasal concentration (0.2 mg). At 7 days post-treatment, catecholamine concentrations were determined from the olfactory bulbs and corpus striatum. Concentrations of norepinephrine within both the olfactory bulbs and corpus striatum of mice receiving the intranasal infusion of MPTP were significantly lower than those of the intranasal saline and intraperitoneal MPTP-treated mice. No significant differences in olfactory bulb or corpus striatal dopamine concentrations were obtained as a function of these treatments. These results demonstrate that intranasal infusion of MPTP at low concentrations (similar to 7.0 mg/kg) can significantly reduce noradrenergic, but not dopaminergic, concentrations within the olfactory bulbs and corpus striatum. By contrast, equivalent concentrations of MPTP administered through intraperitoneal injection were without effect. It appears that the olfactory system may represent a particularly sensitive route for the receipt and transport of the neurotoxin MPTP into the brain.