Peter Drummond

Purpose: Complex regional pain syndrome (CRPS) is a neuropathic pain condition that can be acquired after minor trauma or surgery to soft tissues and nerves. Biopsies from affected tissue show an increased density of α1-adrenergic receptors (AR1) compared to controls. In order to further study the role of AR1 in CRPS, we wish to use an immortalized cortical neuron cell line, NIE115. The present study aimed to (i) characterise the expression of AR1 on NIE115 cells and (ii) document how the metabolic profile of NIE115 cells is affected by adrenergic pharmacological intervention. Methods: NIE115 cultures (n = 15) were dual-or triple-labelled with antibodies directed against AR1 as well as specific neuronal markers (neurofilament, TRPV1, TUJ1, CGRP). Cells were then exposed to an AR1 agonist (phenylephrine, n = 18), an antagonist (prazosin, n = 12) or a combination of both (n = 12) and the biochemical effects studied using gas chromatography-mass spectrometry-based metabolomics. Results: Immunohistochemistry confirmed the presence of AR1 on the NIE115 cells. Treatment of the cells with phenylephrine led to changes in both carbon and nitrogen metabolism consistent with stimulation of AR1. It was expected that prazosin would block the metabolic effects of phenylephrine, but a different set of changes to carbon and nitrogen metabolism were observed. This provides further evidence to the observations that prazosin may in fact be acting as an inverse agonist. Conclusion: These data indicate that metabolomics is a powerful technology in the study of receptor signaling, and have provided us with a new tool to investigate CRPS.