A CB2 agonist relieved nerve pain in mice even without CB1 receptors, working through anti-inflammatory pathways | Research

The takeaway

The CB2 receptor agonist AM1710 reversed neuropathic pain in mice regardless of whether they had CB1 receptors, working by reducing inflammatory cytokines and increasing the anti-inflammatory cytokine IL-10 in the spinal cord.

Pain researchers, cannabinoid pharmacologists developing CB2-selective drugs, and clinicians interested in non-psychoactive cannabinoid therapies.

CB2 agonist reversed pain equally in CB1 knockout and wildtype mice

What the researchers found

AM1710 reversed mechanical allodynia to sham levels in CB1 knockout, heterozygous, and wildtype mice via both peripheral (i.p.) and spinal (i.t.) routes. Spinal AM1710 restored IL-10 immunoreactivity in dorsal root ganglia and spinal cord, and reduced pro-inflammatory cytokines. In cell cultures, AM1710 suppressed TNF-alpha production by macrophages.

Why it matters

CB2 agonists that work independently of CB1 could provide pain relief without the psychoactive effects, euphoria, or abuse potential associated with CB1 activation, addressing a major limitation of current cannabinoid therapies.

The numbers in context

AM1710 reversed allodynia to sham levels across all three CB1 genotypes. IL-10 was restored by intrathecal administration. Pro-inflammatory cytokines were reduced in spinal cord (i.t. only) and DRG (both i.p. and i.t.).

How the study worked

Chronic constriction injury model of neuropathic pain in CB1 receptor knockout, heterozygous, and wildtype mice. AM1710 administered intraperitoneally or intrathecally. Immunoreactivity for IL-10 and pro-inflammatory cytokines measured in spinal cord and dorsal root ganglia. Macrophage cultures used for in vitro validation.

What this study cannot tell us

Mouse model of neuropathic pain may not fully represent human conditions. Knockout mice may develop compensatory mechanisms. Only one CB2 agonist tested. Long-term effects and tolerance were not assessed.

How to read the evidence

Well-controlled preclinical study using genetic and pharmacological approaches across multiple mouse genotypes, but animal model limitations apply.

When this study was published

2020 animal study. Supports ongoing development of CB2-selective agonists for pain without psychoactive effects.

The bigger picture

Separating pain-relieving cannabinoid effects from psychoactive ones is a central goal of cannabinoid pharmacology. This study strengthens the case for CB2 as a standalone therapeutic target for neuropathic pain.

Questions still open

Would CB2 agonists be effective for other types of pain beyond neuropathic? Could IL-10 elevation be a biomarker for CB2 agonist efficacy? How close are CB2-selective agonists to clinical trials for pain?

Common questions

Why does it matter that AM1710 works without CB1?

CB1 receptors mediate the psychoactive "high" from cannabis. A drug that relieves pain through CB2 alone could provide cannabinoid-based pain relief without intoxication, euphoria, or abuse potential.

What is IL-10?

Interleukin-10 (IL-10) is an anti-inflammatory cytokine that helps resolve inflammation. This study found that the CB2 agonist boosted IL-10 in areas involved in pain processing, suggesting an anti-inflammatory mechanism for pain relief.

Read the original research

Peripheral versus central mechanisms of the cannabinoid type 2 receptor agonist AM1710 in a mouse model of neuropathic pain.

Brain and behavior, 10(12), e01850

View on PubMed ↗Publisher’s paper ↗

Citation

Wilkerson, Jenny L; Alberti, Lauren B; Kerwin, Audra A; Ledent, Catherine A; Thakur, Ganesh A; Makriyannis, Alexandros; Milligan, Erin D. (2020). Peripheral versus central mechanisms of the cannabinoid type 2 receptor agonist AM1710 in a mouse model of neuropathic pain.. Brain and behavior, 10(12), e01850. https://doi.org/10.1002/brb3.1850