Photo of Susan Ingram, Ph.D.

Susan Ingram Ph.D.

  • (503) 494-1220
    • Associate Professor of Neurological Surgery School of Medicine

My research is focused on understanding neuronal mechanisms of synaptic plasticity involved in pain and drug addiction circuits. One area of current research is focused on identifying intracellular signaling pathways involved in morphine tolerance and dependence using in vitro brain-slice recordings and in vivo behavioral assays. Our experiments focus on how mu opioid receptors (MOPrs) in the periaqueductal gray area (PAG) modulate neuronal excitability and synaptic transmission of PAG neurons. MOPrs are an integral part of the endogenous descending antinociceptive pathway that decreases pain impulses in the spinal cord. Repeated and continuous opioid administration induces neural changes in this system. A second area of research in my laboratory is the dopamine transporter (DAT) and an associated chloride current that I identified in midbrain dopamine neurons. The DAT is one of a family of transporters that are the main targets for psychostimulants, such as amphetamine and cocaine. These transporters are also targets for therapeutic drugs for disorders including depression and attention deficit disorder. Although the transporters are primarily known for regulating extracellular concentrations of neurotransmitters through reuptake of released neurotransmitters, they have significant electrical activities as well. My recent studies determined that these transporters have a role in modulating excitability of midbrain neurons.


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  • B.A., Bowdoin College, Brunswick Maine 1990
  • Ph.D., Oregon Health & Science University, Portland Oregon 1996


  • "Compensatory activation of cannabinoid CB2 receptor inhibition of GABA release in the rostral ventromedial medulla in inflammatory pain." Journal of Neuroscience In: , Vol. 37, No. 3, 18.01.2017, p. 626-636.
  • "Sex differences in GABA signaling in the periaqueductal gray induced by persistent inflammation." Journal of Neuroscience In: , Vol. 36, No. 5, 03.02.2016, p. 1669-1681.
  • "Ligand-biased activation of extracellular signal-regulated kinase 1/2 leads to differences in opioid induced antinociception and tolerance." Behavioural Brain Research In: , Vol. 298, 01.02.2016, p. 17-24.
  • "GABAergic transmission and enhanced modulation by opioids and endocannabinoids in adult rat rostral ventromedial medulla." Journal of Physiology In: , Vol. 593, No. 1, 01.01.2015, p. 217-230.
  • "Change in functional selectivity of morphine with the development of antinociceptive tolerance." British Journal of Pharmacology In: , Vol. 172, No. 2, 2015, p. 549-561.
  • "Amphetamine Modulates Excitatory Neurotransmission through Endocytosis of the Glutamate Transporter EAAT3 in Dopamine Neurons." Neuron In: , Vol. 83, No. 2, 16.07.2014, p. 404-416.
  • "Pain : Novel analgesics from traditional Chinese medicines." Current Biology In: , Vol. 24, No. 3, 03.02.2014.
  • "Contribution of adenylyl cyclase modulation of pre- and postsynaptic GABA neurotransmission to morphine antinociception and tolerance." Neuropsychopharmacology In: , Vol. 39, No. 9, 2014, p. 2142-2152.
  • "Chronic inflammatory pain prevents tolerance to the antinociceptive effect of morphine microinjected into the ventrolateral periaqueductal gray of the rat." Journal of Pain In: , Vol. 14, No. 12, 12.2013, p. 1601-1610.
  • "A New Take on Uptake : Dopamine Transporters and the Cellular Mechanisms of Amphetamine Action."   Catecholamine Research in the 21st Century: Abstracts and Graphical Abstracts, 10th International Catecholamine Symposium, 2012. Elsevier Inc., 2013. p. 44.
  • "Differential control of opioid antinociception to thermal stimuli in a knock-in mouse expressing regulator of G-protein signaling-insensitive Gαo protein." Journal of Neuroscience In: , Vol. 33, No. 10, 06.03.2013, p. 4369-4377.
  • "Columnar distribution of catecholaminergic neurons in the ventrolateral periaqueductal gray and their relationship to efferent pathways." Synapse In: , Vol. 67, No. 2, 02.2013, p. 94-108.
  • "Regulation of μ-opioid receptors : Desensitization, phosphorylation, internalization, and tolerance." Pharmacological Reviews In: , Vol. 65, No. 1, 2013, p. 223-254.
  • "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 In: , Vol. 13, No. 8, 08.2012, p. 799-807.
  • "Chronic psychostimulant exposure to adult, but not periadolescent rats reduces subsequent morphine antinociception." Pharmacology Biochemistry and Behavior In: , Vol. 101, No. 4, 06.2012, p. 538-543.
  • "A sensitive membrane-targeted biosensor for monitoring changes in intracellular chloride in neuronal processes." PLoS One In: , Vol. 7, No. 4, e35373, 10.04.2012.
  • "Association of mu-opioid and NMDA receptors in the periaqueductal gray : What does it mean for pain control." Neuropsychopharmacology In: , Vol. 37, No. 2, 01.2012, p. 315-316.
  • "Tolerance to the antinociceptive effect of morphine in the absence of short-term presynaptic desensitization in rat periaqueductal gray neurons." Journal of Pharmacology and Experimental Therapeutics In: , Vol. 335, No. 3, 12.2010, p. 674-680.
  • "Opioid receptor internalization contributes to dermorphin-mediated antinociception." Neuroscience In: , Vol. 168, No. 2, 06.2010, p. 543-550.
  • "Functional characterization of rhesus embryonic stem cell-derived serotonin neurons." Experimental Biology and Medicine In: , Vol. 235, No. 5, 05.2010, p. 649-657.
  • "The Brainstem and Nociceptive Modulation."  The Senses: A Comprehensive Reference. Vol. 5 Elsevier Inc., 2010. p. 593-626.
  • "Extracellular signal-regulated kinase 1/2 activation counteracts morphine tolerance in the periaqueductal gray of the rat." Journal of Pharmacology and Experimental Therapeutics In: , Vol. 331, No. 2, 11.2009, p. 412-418.
  • "Glutamate modulation of antinociception, but not tolerance, produced by morphine microinjection into the periaqueductal gray of the rat." Brain Research In: , Vol. 1295, 12.10.2009, p. 59-66.
  • "Role of protein kinase C in functional selectivity for desensitization at the μ-opioid receptor : From pharmacological curiosity to therapeutic potential." British Journal of Pharmacology In: , Vol. 158, No. 1, 09.2009, p. 154-156.
  • "Contribution of dopamine receptors to periaqueductal gray-mediated antinociception." Psychopharmacology In: , Vol. 204, No. 3, 06.2009, p. 531-540.
  • "Behavioral consequences of delta-opioid receptor activation in the periaqueductal gray of morphine tolerant rats." Neural Plasticity In: , Vol. 2009, 516328, 2009.
  • "Tolerance to repeated morphine administration is associated with increased potency of opioid agonists." Neuropsychopharmacology In: , Vol. 33, No. 10, 09.2008, p. 2494-2504.
  • "Microinjection of the vehicle dimethyl sulfoxide (DMSO) into the periaqueductal gray modulates morphine antinociception." Brain Research In: , Vol. 1204, 14.04.2008, p. 53-58.
  • "Analgesic tolerance to microinjection of the μ-opioid agonist DAMGO into the ventrolateral periaqueductal gray." Neuropharmacology In: , Vol. 52, No. 8, 06.2007, p. 1580-1585.
  • "Behavioral and electrophysiological evidence for opioid tolerance in adolescent rats." Neuropsychopharmacology In: , Vol. 32, No. 3, 03.2007, p. 600-606.

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