Many traditional analgesics have insufficient efficacy, and therefore continued research is of high importance. Recently, we have developed a hypothesis for peripheral cannabinoid antihyperalgesia/antiallodynia via ionotropic cannabinoid receptors. We propose to test the central hypothesis that peripheral cannabinoid antihyperalgesia/ antiallodynia is mediated, at least in part, by peripheral ionotropic receptors. Our original preliminary data demonstrated that application of cannabinoids to sensory neurons leads to: 1) activation of protein phosphatase 2B (i.e., calcineurin); 2) dephosphorylation of TRPV1; and 3) inhibition of TRPV1 activity in a fashion reversed by calcineurin antagonists. Since the original submission, we have discovered that arachidonyl-2-chloroethylamide (ACEA) selectively activates TRPV1 in transfected CHO cells, whereas WIN selectively activates TRPA1, and that AM1241 preferentially activates a heretofore unreported TRPV1/TRPA1 heteromultimer. Although these cannabinoids differ in their activation of TRP channels, they share the ability to desensitize multiple TRP channels and this may be an important property in peripheral analgesia. Moreover, peripheral cannabinoid antihyperalgesia in rats is blocked by a calcineurin antagonist, suggesting that these peripheral effects might be mediated, in part, by ionotropic receptors.
Specific Aim #1; Determine whether cannabinoid pretreatment activates specific calcineurin catalytic subunits(Aa, Ap, or Ay) leading to dephosphorylation of TRPVI or TRPA1.
Specific Aim #2 : Determine whether TRPV1 is required to mediate the peripheral antihyperalgesic/antiallodynic effects of certain cannabinoids.
Specific Aim #3 : Determine whether TRPA1 is required to mediate the peripheral antihyperalgesic/antiallodynic effects of certain cannabinoids. If the hypothesis of ionotropic receptors mediating peripheral cannabinoid antihyperalgesia/antiallodynia is confirmed, then we believe that it will be an important and conceptually innovative discovery for several reasons: First, this is the first demonstration of a functional implication of ionotropic receptors for peripheral cannabinoid antihyperalgesia/antiallodynia. Second, identification of cannabinoid modulation of pain via TRPchannels provides a rationale for a novel class of analgesics that are devoid of classical cannabinoid side effects.
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