Two different neural pathways regulate loss and regain of
consciousness during
general anesthesia

University of Pennsylvania School of Medicine researchers have
answered
long-running questions about the way that anesthetics act on the body,
by
showing that the cellular pathway for emerging from anesthesia is
different from
the one that drugs take to put patients to sleep during operations.
The findings
will be published this week in Proceedings of the National Academy of
Sciences.

The research focuses on orexins, the small, specialized fraction of
the brain's
100 billion neurons that play a key role in regulating the body's
wakeful state.
Studying mice whose orexin systems had been genetically destroyed - a
state
similar to humans suffering from narcolepsy, a neurological condition
that
causes unusual daytime sleepiness - Max B. Kelz, MD, PhD, an assistant
professor
in Penn's Department of Anesthesiology and Critical Care and the
Mahoney
Institute of Neurological Sciences, found that these mice took much
longer to
emerge from general anesthesia than those with normal orexin signaling
systems.
However, the mice with faulty orexin systems did not appear to fall
asleep
faster during anesthesia, which suggests that different processes are
at play
when transitioning to and from the anesthetized stated.

"The modern expectation is that anesthesiologists can simply flip a
consciousness switch as easily as we might turn the room lights on or
off," says
lead author Max B. Kelz, MD, PhD, an assistant professor in Penn's
Department of
Anesthesiology and Critical Care and the Mahoney Institute of
Neurological
Sciences. "However, what patients do not realize is that despite 160
years of
widespread clinical use, the mechanisms through which the state of
anesthesia
arises and dissipates remain unknown."

Kelz became interested in these questions after treating a narcoleptic
patient
who took more than six hours to regain consciousness after anesthesia,
compared
to the typical six minutes or so. By probing what's different about
the
narcoleptic brain, the Penn study has established for the first time
that the
process of entry into and exit from the anesthetized state are not
mirror images
of one another.

Source: University of Pennsylvania
http://www.physorg.com/news119294281.html