Intranasal administration of glial-derived neurotrophic factor (GDNF) rapidly and significantly increases whole-brain GDNF level in rats.

Previous studies have shown that glial cell line-derived neurotrophic factor (GDNF) exerts significant neuroprotective effects on substantia nigra (SN) neurons in the rat 6-hydroxydopamine (6-OHDA) model of Parkinson's disease (PD). In this study we used enzyme-linked immunosorbent assay (ELISA) to determine GDNF brain levels and distribution to target regions (i.e. striatum and SN) following intranasal administration of GDNF at different time points after administration. Brain levels increased significantly within 1h following a single 50-µg dose of GDNF in a liposomal formulation, returning to baseline by 24h. In a second study, different doses of GDNF (10-150 µg) in phosphate-buffered saline (PBS) were studied at the 1-h time point. Dose-dependent increases in brain GDNF levels were observed with apparent saturation of uptake at doses above 100 µg. Liposomes delivered 10-fold more GDNF to brain than PBS despite yielding similar neuroprotective efficacy in the 6-OHDA model, suggesting incomplete release of GDNF from liposomes in tissue. In a third study, autoradiography was performed on brain sections taken 1h after intranasal (125)I-labeled GDNF. Radioactivity was detected throughout the brain along the rostral-to-caudal axis, indicating that nasally administered GDNF can reach target areas. Collectively, these results demonstrate that intranasal administration of GDNF in liposomes or PBS achieves significant increases in GDNF in target brain areas, supporting use of intranasal administration as a non-invasive means of delivering GDNF to the brain to protect dopamine neurons and arrest disease progression in PD.

Comparison of the binding of the irreversible monoamine oxidase tracers, [(11)C]clorgyline and [(11)C]l-deprenyl in brain and peripheral organs in humans.

The monoamine oxidase A and B (MAO A and B) radiotracers [(11)C]clorgyline (CLG) and [(11)C]L-deprenyl (DEP) and their deuterium labeled counterparts (CLG-D and DEP-D) were compared to determine whether their distribution and kinetics in humans are consistent with their physical, chemical and pharmacological properties and the reported ratios of MAO A:MAO B in post-mortem human tissues. Irreversible binding was consistently higher for DEP in brain, heart, kidneys and spleen but not lung where CLG >DEP and not in thyroid where there is no DEP binding. The generally higher DEP binding is consistent with its higher enzyme affinity and larger free fraction in plasma while differences in regional distribution for CLG and DEP in brain, heart, thyroid and lungs are consistent with different relative ratios of MAO A and B in humans.