Spinal Endocannabinoids Stayed Unchanged Despite Other Regional Findings in a Mouse Morphine Study

A mouse study of prolonged HIV-protein exposure and escalating morphine found region-dependent lipid and inflammatory changes. Spinal endocannabinoid levels were not affected by morphine in the reported comparison, even though other biological measures changed.

The exposures were not cannabis treatment

The experiment used a transgenic HIV-1 Tat model and morphine administration. Researchers measured endocannabinoids and related lipids rather than administering THC. Endocannabinoid observations in this setting cannot be relabeled as evidence that marijuana improves HIV-associated pain or neurological injury.

Lipid classes and brain regions differed

The abstract described striatal increases in related non-endocannabinoid lipids, including OEA and PEA, during morphine exposure. In the spinal cord, morphine changed selected amino acids without changing the assessed endocannabinoids or related lipids. A statement that endocannabinoids increased everywhere would therefore misidentify both the chemical category and the region.

Inflammation assays did not all agree

Cellular and cytokine measures changed, while PET imaging did not show an increase in the examined neuroinflammatory signal. That null imaging finding does not negate every tissue observation. The techniques measure different features, so their disagreement limits a broad claim of either universal inflammation or universal absence of inflammation.

Interpreting the evidence

The study illustrates why sample region, analyte class and assay belong in a mechanistic explanation. It does not establish a THC treatment effect, a human clinical benefit or equivalence between imaging and tissue markers.

Related reading: related lipids and cannabinoid-receptor action.

Research reference

Hermes DJ; Jacobs IR; Key MC; et al. (2020). Escalating morphine dosing in HIV-1 Tat transgenic mice with sustained Tat exposure reveals an allostatic shift in neuroinflammatory regulation accompanied by increased neuroprotective non-endocannabinoid lipid signaling molecules and amino acids. Journal of neuroinflammation. doi:10.1186/s12974-020-01971-6. Evidence basis: study abstract.