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Syrett M, Reed NR, Reed WR, Richey ML, Frolov A, Little JW. Sex-Related Pain Behavioral Differences following Unilateral NGF Injections in a Rat Model of Low Back Pain. BIOLOGY 2022; 11:biology11060924. [PMID: 35741445 PMCID: PMC9219698 DOI: 10.3390/biology11060924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 06/10/2022] [Accepted: 06/11/2022] [Indexed: 11/16/2022]
Abstract
Low back pain (LBP) is a globally prevalent and costly societal problem with multifactorial etiologies and incompletely understood pathophysiological mechanisms. To address such shortcomings regarding the role of neurotrophins in the underlying mechanisms of pain, an LBP model was developed in rats involving two unilateral intramuscular injections of nerve growth factor (NGF) into deep trunk muscles. To date, behavioral investigations of this NGF-LBP model have been limited, especially as it pertains to female pain behaviors. This study compared mechanical sensitivity to noxious (hyperalgesia) and non-noxious (hypersensitivity) stimuli in control and NGF-injected male and female rats through pain resolution. Although the baseline testing revealed no differences between males and females, NGF-injected females demonstrated prolonged ipsilateral deep trunk mechanical hyperalgesia that resolved seven days later than males. Moreover, females showed bilateral trunk mechanical sensitivity to noxious and non-noxious stimuli compared to only ipsilateral behaviors in males. Sex differences were also observed in the severity of behavioral responses, with females displaying greater mean differences from baseline at several timepoints. Overall, these NGF-LBP behavioral findings mirror some of the sex differences reported in the clinical presentation of LBP and accentuate the translatability of this NGF-LBP model. Future studies using this LBP-NGF model could help to elucidate the neurobiological mechanisms responsible for the development, severity, and/or resolution of muscular LBP as well as to provide insights into the processes governing the transition from acute to chronic LBP.
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Affiliation(s)
- Michael Syrett
- Saint Louis University School of Medicine, 1402 South Grand Blvd., Saint Louis, MO 63104, USA; (M.S.); (N.R.R.); (M.L.R.); (A.F.)
| | - Nicholas R. Reed
- Saint Louis University School of Medicine, 1402 South Grand Blvd., Saint Louis, MO 63104, USA; (M.S.); (N.R.R.); (M.L.R.); (A.F.)
| | - William R. Reed
- Department of Physical Therapy, University of Alabama at Birmingham, 1720 2nd Ave. South, Birmingham, AL 35294, USA;
| | - Madison L. Richey
- Saint Louis University School of Medicine, 1402 South Grand Blvd., Saint Louis, MO 63104, USA; (M.S.); (N.R.R.); (M.L.R.); (A.F.)
| | - Andrey Frolov
- Saint Louis University School of Medicine, 1402 South Grand Blvd., Saint Louis, MO 63104, USA; (M.S.); (N.R.R.); (M.L.R.); (A.F.)
| | - Joshua W. Little
- Saint Louis University School of Medicine, 1402 South Grand Blvd., Saint Louis, MO 63104, USA; (M.S.); (N.R.R.); (M.L.R.); (A.F.)
- Correspondence:
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