Female mice developed tolerance to THC pain relief faster than males in chronic pain model | Research

The takeaway

In mice with chemotherapy-induced neuropathic pain, females acquired tolerance to THC anti-pain effects faster than males at both doses tested.

Pain researchers, pharmacologists studying cannabinoid tolerance, and clinicians considering sex-based dosing.

Females acquired THC tolerance faster than males at both doses tested

What the researchers found

Female mice developed tolerance to the anti-allodynic (pain-relieving) effects of both 6 mg/kg and 10 mg/kg THC faster than males. A mutation (S426A/S430A) designed to reduce CB1 receptor desensitization did not alter tolerance development in either sex. THC pain relief was blocked by the CB1 antagonist rimonabant and partially blocked by the CB2 inverse agonist SR144528.

Why it matters

Tolerance to cannabinoid pain relief is a major clinical limitation. The finding that females develop tolerance faster has direct relevance for dosing considerations, as women may need different treatment strategies for long-term cannabinoid pain management.

The numbers in context

Two THC doses tested: 6 and 10 mg/kg. Females developed tolerance faster at both doses. S426A/S430A mutation did not alter tolerance. Rimonabant (CB1 antagonist) fully blocked THC effects. SR144528 (CB2 inverse agonist) partially blocked effects.

How the study worked

Male and female S426A/S430A mutant mice and wild-type littermates received four weekly cisplatin injections (5 mg/kg) to induce chronic neuropathic pain. Mice were then tested for tolerance to THC anti-allodynic effects at 6 and 10 mg/kg doses. CB1 and CB2 receptor involvement was confirmed with selective antagonists.

What this study cannot tell us

Mouse model may not directly translate to human pain. Cisplatin-induced neuropathy is a specific pain type. Only two THC doses tested. The S426A/S430A mutation finding is negative, limiting mechanistic insight.

How to read the evidence

Well-controlled animal study with genetic and pharmacological tools. Preliminary because findings are in mice and may not translate to humans.

When this study was published

2021 preclinical study in mice.

The bigger picture

Sex differences in cannabinoid tolerance are increasingly recognized across preclinical research. If these findings translate to humans, they could explain why some clinical trials show inconsistent pain relief results when not accounting for sex as a variable.

Questions still open

What molecular mechanisms drive faster tolerance in females? Would intermittent dosing schedules reduce sex differences in tolerance? Do human women develop cannabinoid tolerance faster than men?

Common questions

Why do females develop THC tolerance faster?

The exact mechanism remains unclear. This study tested whether the GRK/beta-arrestin-2 desensitization pathway was responsible (using S426A/S430A mutant mice) but found it was not, suggesting other mechanisms drive the sex difference.

Did THC work through CB1 or CB2 receptors for pain relief?

Primarily CB1. The CB1 antagonist rimonabant completely blocked THC pain relief, while the CB2 inverse agonist only partially blocked it, indicating CB1 is the main target with some CB2 contribution.

Read the original research

Sex Differences in Tolerance to Delta-9-Tetrahydrocannabinol in Mice With Cisplatin-Evoked Chronic Neuropathic Pain.

Frontiers in molecular biosciences, 8, 684115

View on PubMed ↗Publisher’s paper ↗

Citation

Henderson-Redmond, Angela N; Crawford, LaTaijah C; Sepulveda, Diana E; Hale, David E; Lesperance, Julia J; Morgan, Daniel J. (2021). Sex Differences in Tolerance to Delta-9-Tetrahydrocannabinol in Mice With Cisplatin-Evoked Chronic Neuropathic Pain.. Frontiers in molecular biosciences, 8, 684115. https://doi.org/10.3389/fmolb.2021.684115