College of Arts and Sciences

Department of Psychology

Michael M. Morgan


Ph.D. University of California, Los Angeles, 1989

Contact Information:

On Sabbatical 2013/2014
Office: CLS 208G - Vancouver (Regional Campus)
Phone: (360) 546-9726


Personal Web Page

Classes Taught:

  • Psychology 312: Research Methods in Psychology
  • Psychology 372: Introduction to Physiological Psychology
  • Psychology 401: Historical Development of Psychology
  • Psychology 473: Advanced Physiological Psychology
  • Psychology 504: History of Psychology: Theoretical and Scientific Foundations

Research Interests:

  • Pain Modulation
  • Tolerance to Opiods

Pain messages traveling from the skin to the brain are subject to powerful modulation in the spinal cord. This modulation can occur by direct application of narcotics to the spinal cord or via descending messages from the brain. The primary descending system involved in pain modulation runs from the periaqueductal gray (PAG) to the rostral ventromedial medulla (RVM) to the spinal cord. Microinjection of narcotics such as morphine into the PAG or RVM inhibit pain throughout the body. The research in my laboratory focuses on role of the PAG and RVM in pain modulation, and the contributions of these structures to opioid tolerance.

Function of the PAG & RVM: Insights into the function of the PAG and RVM can be revealed by examining the behavioral effects evoked from direct application of drugs (e.g., opioids, excitatory amino acids) into the PAG or RVM of awake rats. The running, jumping, and immobility produced by activation of PAG and/or RVM neurons indicate that the function of these structures is the integration of defensive reactions of which pain inhibition is merely one component.

Opiod Tolerance: Tolerance to the antinociceptive effect of microinjecting opioids such as morphine into the ventrolateral PAG develops with repeated administration. Current research is aimed at identifying the intracellular signaling molecules that contribute to opioid tolerance.

Behavioral Consequences of Ligand-Biased Signaling: Injection of opioids into the PAG inhibit pain by binding to mu-opioid receptors. We currently are examining how administration of different mu-opioid receptor agonists (e.g., morphine, fentanyl, DAMGO) into the PAG vary in the analgesia produced and signaling molecules activated. This ligand biased signaling is particularly evident in the mechanisms underlying tolerance to opioids.

Selected Publications:

Mehalick, M. L., Ingram, S. L., Aicher. S. A., & Morgan, M. M. (in press). Chronic inflammatory pain prevents tolerance to the antinociceptive effect of morphine microinjected into the ventrolateral periaqueductal gray of the rat. Journal of Pain.

Suckow, S. K., Deichsel, E. L., Ingram, S. L., Morgan, M. M., & Aicher. S. A. (2013). Columnar distribution of catecholaminergic neurons in the ventrolateral periaqueductal gray (vlPAG) and their relationship to efferent pathways. Synapse, 67:94-108. PMID: 23152302

Wilson-Poe, A. R., Pocius, E., Herschbach, M., & Morgan, M. M. (2013). The periaqueductal gray contributes to bidirectional enhancement of antinociception between morphine and cannabinoids. Pharmacology, Biochemistry & Behavior, 103:444-449. PMID: 23063785

Bobeck, E. N., Haseman, R. A., Hong, D., Ingram, S. L., & Morgan, M. M. (2012). Differential development of antinociceptive tolerance to morphine and fentanyl is not linked to efficacy in the ventrolateral periaqueductal gray of the rat. Journal of Pain, 13(8):799-807. PMID 22766006

Wilson-Poe, A.R., Morgan, M.M., Aicher, S.A., & Hegarty, D.M. (2012). Distribution of CB1 Cannabinoid Receptors and Their Relationship with Mu-Opioid Receptors in the Rat Periaqueductal Gray. Neuroscience, 213: 191-200. PMID: 22521830

Cyr, M.C., Ingram, S.L., Aicher, S.A., Morgan, M.M. (2012). Chronic psychostimulant exposure to adult, but not periadolescent rats reduces subsequent morphine antinociception. Pharmacology, Biochemistry, and Behavior, 101:538-543. PMID: 22405777

    Michael M. Morgan
Department of Psychology, Washington State University, Pullman WA 99164-4820, 509-335-2631, Contact Us