A role for the anandamide membrane transporter in TRPV1-mediated neurosecretion from trigeminal sensory neurons

Many n-acylethanolamines utilize the anandamide membrane transporter (AMT) to gain facilitated access to the intracellular compartment, hence, we hypothesized that this mechanism might be important for anandamide (AEA)- and N-arachidonoyl-dopamine (NADA)-evoked CGRP release from cultured trigeminal ganglion (TG) neurons. Using [C-14]AEA we demonstrated that TG neurone transported AEA in a FAAH- and AMT-inhibitable fashion. Although TRPV1-positive TG neurons were found to express fatty acid amide hydrolase, the application of FAAH inhibitors had no effect on AEA-evoked CGRP release. In contrast, application of the AMT inhibitors OMDM-2 or VDM-11 significantly reduced the potency and efficacy of AEA-, NADA- and capsaicin-evoked CGRP release. Moreover OMDM-2 (IC50 values ranging from 6.4-9.6 mu M) and VDM-11 (IC50 values ranging from 5.3-11 mu M) inhibited CGRP release evoked by EC80 concentrations of AEA, NADA and CAP and these values were consistent with IC50, obtained for inhibition of uptake. OMDM-2 had no effect on CGRP release per se while VDM-11 evoked CGRP release on its own (EC50 similar to 35 mu M) in a CPZ-insensitive, but ruthenium red (RR)-sensitive fashion. This is the first demonstration that TG sensory neurons possess an AMT-like mechanism suggesting that this mechanism is important for the pharmacological action of AEA and NADA at native TRPV1 channels. (c) 2005 Elsevier Ltd. All rights reserved.