The limitations of the currently available treatments for chronic neuropathic pain highlight the need for safer and more effective alternatives. The authors carried out a focused review using a systems biology approach to integrate the complex mechanisms of nociception and neuropathic pain, and to decipher the effects of nitrous oxide (N2O) on those pathways, beyond the known effect of N2O on N-methyl-D-aspartate receptors. This review identified a number of potential mechanisms by which N2O could impact the processes involved in peripheral and central sensitization. In the ascending pathway, the effects of N2O include activating TWIK-related K+ channel 1 potassium channels on first-order neurons, blocking voltage-dependent calcium channels to attenuate neuronal excitability, attenuating postsynaptic glutamatergic receptor activation, and possibly blocking voltage-dependent sodium channels. In the descending pathway, N2O induces the release of endogenous opioid ligands and stimulates norepinephrine release. In addition, N2O may mediate epigenetic changes by inhibiting methionine synthase, a key enzyme involved in DNA and RNA methylation. This could explain why this short-acting analgesic has shown long-lasting anti-pain sensitization effects in animal models of chronic pain. These new hypotheses support the rationale for investigating N2O, either alone or in combination with other analgesics, for the management of chronic neuropathic pain.
Keywords: CPNP; N2O; central nervous system; chronic peripheric neuropathic pain; integrative biology; laughing gas; medical gas; neuralgia; peripheral nervous system; receptors.