Formalin-induced pain is reduced in σ1 receptor knockout mice

The role of σ1 receptors in non-acute pain has not been explored. In this study we show that both phases of formalin-induced pain were reduced by approximately 55% in σ1 receptor knockout mice in comparison to wild-type animals. These results suggest that the tonic pain induced by formalin is altered in mice lacking σ1 receptors, and highlight the potential usefulness of further studies of the role of σ1 receptors in models of non-acute pain.