Professor
Department of Psychology
WSU Vancouver
E-Mail:
morgan@vancouver.wsu.edu
Phone: (360) 546-9726
Neural Mechanisms of Pain Modulation and Morphine Tolerance
Morphine inhibits pain by acting at sites throughout the nervous system.
This antinociception is diminished with repeated administration because
of the development of tolerance. The focus of my research is to
determine the neural mechanism underlying this change so better
treatments for pain can be developed.
Morphine inhibits pain, in part, by activating a naturally occurring
pain modulatory system that runs from the periaqueductal gray (PAG) to
rostral ventromedial medulla (RVM) to spinal cord. Microinjection of
morphine into any of these structures inhibits pain. We have shown that
repeated administration of morphine produces tolerance because of
adaptations in the ventrolateral part of the PAG. Subsequent studies
revealed that this change occurs in opioid-sensitive GABAergic neurons
in the PAG. Currently, we are using pharmacological and
electrophysiological techniques to determine the specific neural
adaptation underlying tolerance in these neurons. This work is supported
by the National Institute on Drug Abuse.
For more information on Dr. Morgan's research, see:
http://www.vancouver.wsu.edu/fac/morgan/morgan_home.html
Biographical Information
Michael Morgan was an undergraduate and graduate student at the
University, California at Los Angeles (UCLA) earning a B.A. (1984), M.A.
(1985), and Ph.D. (1989) degree in Psychology (Physiological Psychology
emphasis). He continued his education in the Department of Neurology at
the University of California, San Francisco as a postdoctoral fellow
from 1989 to 1993. Dr. Morgan has been in the Department of Psychology
at Washington State University Vancouver since 1993. He is the only
member of the Vancouver faculty to receive the Students Award for
Teaching Excellence and the Chancellors Award for Research Excellence.
Recent Publications
Ingram, S.L., Fossum, E.N., &
Morgan, M.M. (2006). Behavioral and
electrophysiological evidence for opioid tolerance in adolescent rats.
Neuropsychopharmacology.
Morgan, M. M., Fossum, E. N., Stalding, B. M., & King, M. M. (2006).
Morphine antinociceptive potency on chemical, mechanical, and thermal
nociceptive tests in the rat. J. Pain, 7:358-366.
Morgan, M. M., Tierney, B. W., & Ingram, S. L. (2005). Intermittent
dosing prolongs tolerance to the antinociceptive effect of morphine
microinjection into the periaqueductal gray. Brain Research,
1059:173-178.
Lane, D. A., Patel, P. A., &
Morgan, M. M. (2005). Evidence for an
intrinsic mechanism of antinociceptive tolerance within the
ventrolateral Periaqueductal Gray of rats. Neuroscience, 135:227-234.
Lane, D. A. &
Morgan, M. M. (2005). Antinociceptive tolerance to
morphine from repeated nociceptive testing in the rat. Brain Research,
1047:65-71.
Morgan, M. M., Clayton, C. C., & Boyer-Quick. J. S., &. (2005).
Differential susceptibility of the PAG and RVM to tolerance to the
antinociceptive effect of morphine in the rat. Pain, 113:91-98.
