Prostaglandins and cannabinoids in peripheral systems

Since their discovery, the prostaglandins have been known to have important roles in the reproductive systems. This has prompted investigators looking for mechanisms to explain the effects of cannabinoids on reproduction to study a possible role for the prostaglandins (Jordan and Castracane, 1976; Ayalon et al, 1977; Dalterio et al, 1978, 1981; Rettori et al., 1990). Cannabinoids appear to modulate PG levels in male and female models where they show both stimulatory and inhibitory actions. In another type of endocrine system, the pancreatic islet, where THC exerts an effect, the involvement of eicosanoids was suggested (Laychock et al., 1986).

Another body system where the prostaglandins play a major role is in the cardiovascular system. Both THC-induced hypotension and bradycardia could be inhibited by the prior administration of aspirin in dogs (Burstein et al., 1982b). The inhibition of THC-induced synthesis of vasoactive prostaglandins could explain this type of response. In a related effect, aspirin inhibited the effects of THC on lung perfusion pressure (Kaymacalan and Turker, 1975).

Intraocular pressure is sensitive to levels of prostaglandins in the eye, and the pressure lowering effect of THC is well known. Evidence has been published supporting the idea that the beneficial effect of THC in glaucoma may be explained by a lowering of intraocular PGE2 (Green and Kim, 1976, 1977; Green and Podos, 1974). Finally, there is some evidence that there are interactions between cannabinoids and prostaglandins that impact on intestinal physiology (Jackson et al., 1976a,b; Coupar and Taylor, 1983).

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