8 December 1999
Work, sleep, work, sleep,....die
by Kate Melville
Constantly feel tired and jetlagged then maybe your body clock is just out of whack. Well the good news is scientists may have discovered a reason why, the bad news is that it won't help you get better sleep just yet.
Researchers from the University of Illinois have identified a molecule in the brain to retina pathway that seems essential to adjusting your bodies' clock. The mystery substance is pituitary adenylyl cyclase-activating peptide (PACAP), whose role in the brains chemistry has so far been unknown. In their studies researchers found that PACAP works in conjunction with glutamate, another molecule in the nerve fibers between the hypothalamus (home of the circadian clock) and the retina.
According to Martha Gillette, of the University of Illinois, "This study provides insight as to how the complex external signals that we encounter daily, such as the range of light intensities, are encoded and communicated to the brain. Light that you experience at night triggers the release of both glutamate and PACAP. The ratio probably depends on the intensity of the light stimulus."
In related prior research Gillette reported in 1994 that glutamate modified the clock in the presence of night light. "PACAP fine tunes the glutamate signal," Gillette said. "Together they convey more than just light is present. They encode information about light properties that is taken back to the clock, allowing it to adjust forward or backward appropriately."
This new study links Gillette's previous work and a more recent study by researchers working for the Danish Medical Research Council who discovered that the PACAP molecule was gathering in the neural pathway, but no one knew quite why this was occurring.
"Adding exogenous PACAP together with glutamate had a negative effect on the amplitude of the clock-resetting effect of glutamate," Gillette said, "the surprise was that when we used fragments of the PACAP peptide as a control, the result was not that of glutamate alone. Rather, the effect was shifted in the opposite direction to increasing PACAP. This meant that PACAP was indeed released from the optic nerve when the glutamate was. It is a normal, silent component of the signal".
This is why bright lights at night keep people awake more effectively than dull or dimmed lights. Bright light delays clock time and makes it harder wake up early the next day. So the more PACAP in the light signal the greater delay.
So for all you insomniacs, Gillette hopes, it's possible to create new drugs to selectively reset a person's sleep cycle.
It was not so long ago that scientists paid little serious attention to sleep research. So what caused this awakening of scientific interest in sleep? Was it great basic science research breakthroughs or scientists more cynically trying focusing on areas of work that might be more easily commercialized? One could say that improving peoples sleep simply leads to better social health, but on the other hand the imperative may less ultraistic. If one views humans as mere 'economic units' who perform better when well rested, then the commercial drive (and funding) for this of this sort research may be far more attractive to many scientists?