Melatonin promotes regeneration of injured motor axons via MT1 receptors.

Melatonin is an ancient multi-tasking molecule produced by the pineal gland and by several extrapineal tissues. A variety of activities has been ascribed to this hormone in different physiological and pathological contexts, but little is known about its role in peripheral neuroregeneration. Here, we have exploited two different types of injury to test the capability of melatonin to stimulate regeneration of motor axons: (a) the acute and reversible presynaptic degeneration induced by the spider neurotoxin α-Latrotoxin and (b) the compression/transection of the sciatic nerve. We found that in both cases melatonin administration accelerates the process of nerve repair. This pro-regenerative action is MT1 -mediated, and at least in part due to a sustained activation of the ERK1/2 pathway. These findings reveal a receptor-mediated, pro-regenerative action of melatonin in vivo that holds important clinical implications, as it posits melatonin as a safe candidate molecule for the treatment of a number of peripheral neurodegenerative conditions.