Antinociceptive and anti-inflammatory effects of choline in a mouse model of postoperative pain

Abstract

Background. Choline is a dietary supplement that activates α7 nicotinic receptors. α7 nicotinic activation reduces cytokine production by macrophages and has antinociceptive activity in inflammatory pain models. We hypothesized that systemic administration of choline would reduce the inflammatory response from macrophages and have antinociceptive efficacy in a murine model of postoperative pain. Methods. We studied the response of wild-type and α7 nicotinic knockout mice to heat and punctate pressure after a model surgical procedure. We investigated the effect of genotype and choline treatment on α-bungarotoxin binding to, and their production of tumour necrosis factor (TNF) from, macrophages. Results. Choline provided moderate antinociception. The ED50 for choline inhibition of heat-induced allodynia was 1.7 mg kg-1 h-1. The ED 50 for punctate pressure threshold was 4.7 mg kg-1 h -1 choline. α7 nicotinic knockout mice had no change in hypersensitivity to heat or pressure and were significantly different from littermate controls when treated with choline 5 mg kg-1 h -1 (P<0.05, 0.01). Choline 100 mM reduced binding of α-bungarotoxin to macrophages by 72% and decreased their release of TNF by up to 51 (sd 11). There was no difference by genotype in the inhibition of TNF release by choline. Conclusions. Systemic choline is a moderately effective analgesic via activation of α7 nicotinic acetylcholine receptors. The antinocicepive effect may not be mediated by a reduction of TNF pathway cytokine release from macrophages. Although choline at millimolar concentrations clearly inhibits the release of TNF, this effect is not α7 subunit-dependent and occurs at concentrations likely higher than reached systemically in vivo. © The Author [2010]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved.