CORTISOL LEVELS IN RESPONSE TO LONGTERM PHYSIOLOGICAL STRESSORS AS A RESULT OF CHRONIC NEUROPATHIC PAIN
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Lyons, Shannon C
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Abstract
The interaction between chronic pain and severe stress is of particular importance considering the increased population experiencing neuropathic pain. We studied the impact of a chronic physical pain stressor on corticosterone levels in rats. Animals underwent spared nerve injury (SNI) surgery or served as sham or naïve controls. A separate group was divided into either acute (1 day) or chronic (5 days) fox urine exposure and served as a reference as to the effects of a purely psychological stress source. The SNI procedure induces physiological stress that can be measured 28 days (chronic pain) post-surgery. Each animal’s plasma was tested using radioimmunoassay with Iodine125 to determine corticosterone levels. While SNI surgery resulted in an increase in corticosterone in both groups as compared to controls, chronic pain rats had less corticosterone than both groups of fox urine exposed rats. The corticosterone reduction in chronic stress rats may be explained by prolonged activation of the hypothalamic pituitary adrenal axis negative feedback loop. This experiment provides insight into the effect of prolonged stress which may lead to future treatment therapies for neuropathic pain.
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Biology, Brain, Neuroscience, Neuropathic pain