Wang Z, Xu B, Jiang C, et al. - Researchers here examined the antinociceptive effects of DN-9 (Tyr-D.Ala-Gly-NMe.Phe-Gly-Pro-Gln-Arg-Phe-NH2) in a series of preclinical pain models and investigated the potential side-effects at the spinal level in mice. Findings revealed the production of analgesia via opioid receptors in the mouse tail-flick test when spinal DN-9 was administered. Decrease in both frequency and amplitude of spontaneous excitatory postsynaptic currents in spinal lamina IIo neurons was observed following DN-9 administration. No production of tolerance or Iba1, c-Fos upregulation was observed with chronic treatment with DN-9. In both inflammatory pain and neuropathic pain, spinal DN-9 produced potent analgesia. Limited opioid-related side effects were observed in relation to intrathecal DN-9.