Spinal CB1 Blockade Affected Both Developing and Established Morphine Tolerance in Rats
Preventing tolerance and reversing an already established response are different experimental questions. A rat study of spinal CB1 signaling examined both in relation to morphine antinociception.
The intervention targeted spinal signaling
Rats with spinal catheters received morphine under acute repeated-dose and longer regimens. Researchers measured thermal and mechanical responses and examined calcitonin gene-related peptide, or CGRP, in spinal tissue and cultured sensory neurons.
The antagonist changed the tolerance pattern
The abstract reports that AM251 coadministration inhibited development of acute and chronic tolerance. In animals already tolerant to morphine, AM251 restored antinociceptive potency under the tested conditions. It also attenuated morphine-related CGRP changes.
These are not interchangeable exposures
Blocking CB1 signaling with an antagonist/inverse agonist is different from giving THC or stimulating cannabinoid receptors. A finding involving receptor blockade cannot be summarized as evidence that cannabis itself reverses opioid tolerance.
The neuronal culture findings add mechanistic context but are not clinical treatment outcomes. Spinal delivery, animal reflexes and selected peptide measurements constrain translation. The work supports investigation of endogenous cannabinoid participation in opioid adaptation without establishing a human combination strategy, a safe medication change or a general treatment for dependence.
Related: interpreting cannabis tolerance claims.
Research cited
Trang T; Sutak M; Jhamandas K. Involvement of cannabinoid (CB1)-receptors in the development and maintenance of opioid tolerance. Neuroscience (2007). doi:10.1016/j.neuroscience.2007.02.031. Findings discussed from the study abstract.
