Research presented here sought to determine if opioid induced tolerance is linked to activity changes within the PI3Kγ-AKT-cGMP-JNK intracellular signaling pathway in spinal cord or peripheral nervous systems. Morphine or saline injections were given subcutaneously twice a day for five days (15 mg/kg) to male C57Bl/6 mice. A separate cohort of mice received spinal nerve ligation (SNL) one week prior to the start of morphine tolerance. Afterwards, spinal cord, dorsal root ganglia, and sciatic nerves were isolated for quantifying total and phosphorylated- JNK levels, cGMP, and gene expression analysis of Pik3cg, Akt1, Pten, and nNos1. This pathway was downregulated in the spinal cord with increased expression in the sciatic nerve of morphine tolerant and morphine tolerant mice after SNL. We also observed a significant increase in phosphorylated- JNK levels in the sciatic nerve of morphine tolerant mice with SNL. Pharmacological inhibition of PI3K or JNK, using thalidomide, quercetin, or SP600125, attenuated the development of morphine tolerance in mice with SNL as measured by thermal paw withdrawal. Overall, the PI3K/AKT intracellular signaling pathway is a potential target for reducing the development of morphine tolerance in the peripheral nervous system. Continued research into this pathway will contribute to the development of new analgesic drug therapies.
Bibliographical noteFunding Information:
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Funding provided by the NIH to AHK (K01 DA042902), the University of Minnesota Integrated Biosciences Graduate Program to T.O., and the University of Minnesota Duluth Undergraduate Research Opportunity Program award to TJ.
© The Author(s) 2021.
- Morphine tolerance
- peripheral nervous system
- spinal nerve ligation
PubMed: MeSH publication types
- Journal Article
- Research Support, N.I.H., Extramural
- Research Support, Non-U.S. Gov't