The goal of this research study is to evaluate whether the central nervous systems of those with low back pain are different from those of healthy, pain-free individuals. Specifically, the researchers will test whether "glial cells" (the immune cells of the brain and spinal cord) are more active in patients with low back pain than in healthy volunteers. The investigators' previous study showed that patients with chronic low back pain demonstrated elevations in brain levels of the 18kDa translocator protein (TSPO), a marker of glial activation. To test this hypothesis, the study team will image the brains and spinal cords of patients suffering from low back pain using integrated magnetic resonance- positron emission tomography (MR-PET), and a radiotracer called [11C]PBR28, which tracks levels of glial activation. The efficacy of minocycline as a treatment for chronic low back pain will also be evaluated. A recent study demonstrated a statistically significant reduction in pain in those with lumbar radiculopathy after treatment with minocycline, leading the investigators of this study to believe that minocycline may have potential efficacy in treating other back pain populations. The study team will observe whether a short course of minocycline hydrochloride may reduce glial activation along with self-reported low back pain symptoms. To this end, patients will be evaluated clinically and/or re-scanned after completing a 2-week trial of minocycline or placebo (a sugar pill). This study will be enrolling individuals who have been suffering from sub-acute (short-term) and chronic low back pain.
Inclusion Criteria: - the ability to give written informed consent - fluency in English - on a stable pain treatment - Chronic or sub-acute low back pain Exclusion Criteria: - no interventional pain procedures during drug trial - contraindications to MRI and PET scanning (including presence of a cardiac pacemaker or pacemaker wires, metallic particles in the body, vascular clips in the head or previous neurosurgery, prosthetic heart valves, claustrophobia) - pregnancy or breast feeding - any use of recreational drugs in the past 6 months - allergy to minocycline or other tetracyclines, or taking medications known to interact with minocycline - any other contraindications to minocycline administration