Levonantradol: a role for central prostanoid mechanisms?

Although delta 9-tetrahydrocannabinol (THC) possesses many pharmacologic activities, attempts to define sites of biochemical action for the natural cannabinoids have been hampered by their low solubility, their low potency, and their relative lack of biologic selectivity. We have recently described a potent, cannabinoid-related analgetic, levonantradol, which acts stereospecifically in animals to produce analgesia qualitatively similar to morphine but at 1/9 to 1/34 the dose. While levonantradol does not act at or through the opiate receptor, the finding of one-way cross tolerance in animals suggests that morphine and levonantradol influence common nociceptive pathways. This report describes a striking structural homology between PGE1 and levonantradol as elucidated by x-ray and conformational studies. This observation is consistent with the generally recognized involvement of prostaglandins in pain and emesis and may have relevance to the site of levonantradol's analgetic actions. More importantly, it provides an ongoing, heuristic basis for exploring, in depth, the role of prostaglandins in the action of levonantradol and cannabinoids.