The behavioural and neuroprotective outcomes when 670nm and 810nm near infrared light are applied together in MPTP-treated mice.

We have shown previously that when applied separately, 670nm and 810nm near infrared light (NIr) reduces behavioural deficits and offers neuroprotection in a MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model of Parkinson's disease. Here, we explored the beneficial outcomes when these NIr wavelengths were applied both together, either concurrently (at the same time) or sequentially (one after the other). Mice received MPTP injections (total of 50mg/kg) and had extracranial application of 670nm and/or 810nm NIr. Behavioural activity was tested with an open-field test and brains were processed for tyrosine hydroxylase immunohistochemistry and stereology. Our results showed that when 670nm and 810nm NIr were applied both together and sequentially, there was a greater overall beneficial outcome - increased locomotor activity and number of tyrosine hydroxylase immunoreactive cells in the substantia nigra pars compacta - than when they were applied either separately, or in particular, both together and concurrently. In summary, our findings have important implications for future use of NIr therapy in humans, that there are some combinations of wavelengths that provide more beneficial outcome than others.