Figure 4.
Compass points or the cannabinoid cartwheel of complicated cross-talk; green lines with arrow tips represent stimulation/enhancement of the indicated activity; red arrows with ball ends represent inhibition; dashed arrows represent unknown or variable relationships; no line represents no effect. For example, it appears that low levels of intracellular calcium enhance TRPV1, while prolonged/excessive calcium exposure leads to TRPV1 desensitization (c). ERK activity appears to have variable enhancing effects on PPAR activity that may be subtype- or tissue-dependent, but appears to have not been studied with respect to the majority of the endocannabinoid system, other than as a target of receptor activation (d). DAGL, diacylglycerol lipase, ERK, extracellular signal-regulated kinase; FAAH, fatty acid amide hydrolase; PKA, protein kinase A; PKC, protein kinase C; MAGL, monoacylglycerol lipase; NAPE-PLD, N-arylphosphatidylethanolamine-phospholipase D; PPAR, peroxisome proliferator-activated receptor.