Applying antibodies to block the effect of PACAP that might be released from the optic nerve fibers in brain-slice preparations had the same effect. "This meant that PACAP was indeed released from the optic nerve when the glutamate was. It is a normal, silent component of the signal," she said.
This is likely the basis for why bright light at night keeps a person awake more effectively than dim light, Gillette said. Bright light delays clock time more and, thereby, makes it harder to awaken early the next morning. More PACAP in the light signal means a greater delay, she added.
Eventually, Gillette said, it may be possible to create drugs to selectively reset a person's sleep cycle, which would be welcome news for night-shift workers and for some people with sleep disorders.
The co-authors of the paper were Gillette, Dong Chen, Gordon F. Buchanan and Jian M. Ding, all of the U. of I., and Jens Hannibal, a professor of clinical biochemistry at the University of Copenhagen.