The neurotransmitter dopamine -- which is most famously associated with the "reward system" in the brain -- is also linked to eye blink rate and time perception, both of which are in constant flux. Immediately after a blink, time is perceived to go by a little more slowly.
A small pilot study of gene therapy for Parkinson s disease showed improvement in severe motor symptoms. There were no side effects of significance, and all three doses had beneficial effect.