OHSU

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Gregory P. Mark, Ph.D.

Associate Professor, Behavioral Neuroscience
Admin Unit: SOM-Behavioral Neuroscience Department
Phone: (503) 494-2680
Lab Phone: (503) 494-1801
Fax: (503) 494-6877
Office: MRB726
Mail Code: L470
Programs:
Behavioral Neurocience
Neuroscience Graduate Program
Research Interests:
Acetylcholine Animal models of addiction Dopamine Neurochemistry; behavioral » Click here for more about Dr. Mark's research » PubMed Listing
Preceptor Rotations
Academic Term Available Winter 2010 No Fall 2009 No Spring 2010 Yes
Faculty Mentorship
Dr. Mark is available as a mentor for 2010-2011. Dr. Mark is available as a mentor for 2009-2010.
Profile

Major Areas

  • Neurophysiology/neurochemistry of motivation and reward
  • drug addiction 

Summary of Current Research

The research in my laboratory is broadly concerned with exploring the biological bases of motivation, reward, and behavior reinforcement. Much of this effort is centered on understanding the neurochemical substrates that mediate drug reward and ultimately addiction. One important neural pathway underlying these behaviors originates in the area of the ventral midbrain and sends connections to a variety of higher brain structures including the nucleus accumbens, prefrontal cortex, neostriatum, and amygdala. The projections of this pathway communicate with other brain sites using a variety of neurotransmitter systems including dopamine, acetylcholine, GABA, and glutamate. We are interested in determining the neurochemical changes that occur during long-term methamphetamine and cocaine exposure and to what extent each of the neurotransmitters affect drug-seeking behavior.

My research relies on several methodological strategies including neurochemical, behavioral, electrophysiological, and biochemical techniques that are used to investigate the role of the nucleus accumbens, ventral tegmental area, and other limbic structures in the development of conditioned behavior and drug-seeking. In one line of experiments, we use in vivo microdialysis to monitor the release of neurotransmitters in freely-behaving rats during the presentation of primary and secondary rewards. The goal is to determine which alterations in neurotransmitter systems correlate with changes in reward value of drugs and stimuli that are associated with drugs.  Behavioral pharmacology techniques are used to study the impact of receptor specific agonists and antagonists on drug self-administration behavior.

Repeated exposure to drugs such as cocaine and methamphetamine can cause long-term (perhaps permanent) changes in neuronal firing patterns and neurotransmitter output (release), receptor density or effector coupling, signal transduction mechanisms, and gene expression. Through collaborative efforts with other OHSU researchers, we have studied the impact of active (i.e. self-administered) and passive (i.e. response independent) drug exposure on neuronal plasticity and biochemical markers associated with these processes. In several instances, we have found that active drug-seeking causes changes in neurotransmitter levels, neuron firing, and gene expression patterns that are distinctly different from those induced strictly through pharmacological intervention. Identifying and understanding such changes is a critical step toward determining the neural basis of addictive behavior and developing strategies to combat addiction. 

Recent Publications

Hansen, ST & Mark, GP  (2007) The nicotinic acetylcholine receptor antagonist mecamylamine prevents escalation of cocaine self-administration in rats with extended daily access. Psychopharmacology, 194:53-61.

Mark, GP, Kinney, AE, Zhu, X, Finn, DA, Berger, SP, Mader, SL  & Bechtholt, AJ (2006) Injection of oxotremorine in nucleus accumbens shell reduces cocaine but not food self-administration in rats. Brain Research, 1123 (1): 51-59.

DuMont EC, Mark GP, Mader S, Williams JT (2005) Self-administration enhances excitatory synaptic transmission in the bed nucleus of the stria terminalis. Nature Neuroscience. 8(4):413-4.

Mitchell JM, Cunningham CL, Mark GP (2005) Locomotor activity predicts acquisition of self-administration behavior but not cocaine intake. Behavioral Neuroscience. 119(2):464-472.

Education

  • PhD (1988) University of Delaware, Newark

Previous Positions

  • Research Staff Member/Lecturer, Department of Psychology, Princeton University
  • NIH Postdoctoral Fellow, Department of Psychology, Princeton University

Non-Academic Interests