Chronic pain is a debilitating condition that affects one in four Americans, and for which there is a pressing need for safe, effective treatments. Chronic pain patients experience enhanced pain sensations and often experience pain when innocuous stimuli are presented. However, the neural basis for this amplification is poorly understood. Here, we propose to investigate the neural circuit basis for wind-up, a physiological type of central hyperexcitability that may also contribute to persistent pain. The studies we are proposing will begin to identify specific spinal circuitry involved in this amplification, and investigate whether these microcircuits are altered in conditions of injury. This knowledge may elucidate new therapeutic targets for the treatment of pain, which is the long-term goal of research of our program. In the first aim, we will use our novel skin/nerve/DRG/spinal cord preparation combined with optogenetic approaches to examine the involvement of select cell types in wind-up of cutaneous sensory inputs recorded in spinal projection neurons. These studies will examine the roles of specific subsets of cutaneous sensory neurons in wind-up by optogenetic stimulation of their cutaneous projections both in nave mice and following nerve injury. We will also employ optogenetic strategies to activate or inhibit specific subsets of genetically defined excitatory (neurotensin (Nt)-cre) and inhibitory (nNos-creER) spinal interneurons to determine their roles in this process. In the second aim we will examine potential neural network and/or synaptic mechanisms underlying the wind-up of sensory inputs. In particular, we will test the role of persistent, reverberating currents in wind-up. In addition, investigate which mediators cause the slow depolarizing current that is often observed with wind-up, and determine whether this plays a contributing role. In the third aim, we will use a novel behavioral model of wind-up using temporal summation of cutaneous sensory inputs. Specifically, we have developed a behavioral model of temporal summation in mice using the same optogenetic stimulation that we previously used to induce wind-up in the first aim. This will allow us, for the first time, to make a direct correlation between the physiological phenomenon (wind-up) and a behavioral response to the perception of pain (temporal summation), using place-aversion as a measure of nociception in mice. Completion of the studies proposed in this application will provide new insights into spinal circuitry underlying the processing of sensory information, and how these processes are altered following nerve injury. Importantly could provide potential targets for the development of pharmaceutical therapies. These new therapies could provide for improved treatments for the alleviation of the adverse symptoms of chronic neuropathic pain.

Public Health Relevance

Chronic pain is a serious health concern effecting millions of American annually. In this application we are proposing to use innovative genetic tools together with a novel somatosensory preparation to dissect the spinal circuitry involved in processing nociceptive information. These studies will provide new knowledge about how specific spinal network process peripheral sensory information under normal conditions and following peripheral neuropathy that should provide targets for new pharmaceutical therapies for the treatment of chronic pain.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS096705-03
Application #
9545887
Study Section
Somatosensory and Chemosensory Systems Study Section (SCS)
Program Officer
Oshinsky, Michael L
Project Start
2016-09-01
Project End
2021-08-31
Budget Start
2018-09-01
Budget End
2019-08-31
Support Year
3
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Pittsburgh
Department
Biology
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
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