Interaction of local anaesthetic agents with the endogenous norepinephrine transporter in SH-SY5Y human neuroblastoma cells.

Use of intravenous guanethidine for the treatment of complex regional pain syndrome type I is of variable efficacy. Guanethidine injection is painful, so local anaesthetic is co-administered. We hypothesize that local anaesthetic inhibits uptake of guanethidine and hence reduces its efficacy. In this study we have examined the effects of a range of local anaesthetic agents on the uptake of [3H]norepinephrine ([3H]NE) (as a surrogate for guanethidine) and the binding of [3H]nisoxetine to the NE transporter in cultured SH-SY5Y human neuroblastoma cells. All local anaesthetic agents inhibited NE uptake with a rank order cocaine>tetracaine>procaine(esters), dibucaine > bupivacaine > prilocaine > lidocaine (amides). In addition all anaesthetic agents displaced [3H]nisoxetine with a rank order cocaine > tetracaine > dibucaine > procaine > prilocaine > bupivacaine > lidocaine. There was a positive correlation between [3H]NE uptake and [3H]nisoxetine binding. Our data suggest that when local anaesthetic and guanethidine are co-administered the former may reduce uptake of the latter and hence reduce the clinical efficacy of guanethidine.