Opioid-induced hyperalgesia (OIH) is a serious adverse event produced by opioid analgesics. Lack of an model has hindered study of its underlying mechanisms. Recent evidence has implicated a role of nociceptors in OIH. To investigate the cellular and molecular mechanisms of OIH in nociceptors, , subcutaneous administration of an analgesic dose of fentanyl (30 μg/kg, s.c.) was performed in male rats. Two days later, when fentanyl was administered intradermally (1 μg, i.d.), in the vicinity of peripheral nociceptor terminals, it produced mechanical hyperalgesia (OIH). Additionally, two days after systemic fentanyl, rats had also developed hyperalgesic priming (opioid-primed rats), long-lasting nociceptor neuroplasticity manifested as prolongation of prostaglandin E (PGE) hyperalgesia. OIH was reversed, , by intrathecal administration of cordycepin, a protein translation inhibitor that reverses priming. When fentanyl (0.5nM) was applied to dorsal root ganglion (DRG) neurons, cultured from opioid-primed rats, it induced a mu-opioid receptor (MOR)-dependent increase in [Ca] in 26% of small-diameter neurons and significantly sensitized (decreased action potential rheobase) weakly IB4-positive and IB4-negative neurons. This sensitizing effect of fentanyl was reversed in weakly IB4-positive DRG neurons cultured from opioid-primed rats after treatment with cordycepin, to reverse of OIH. Thus, administration of fentanyl induces nociceptor neuroplasticity, which persists in culture, providing evidence for the role of nociceptor MOR-mediated calcium signaling and peripheral protein translation, in the weakly IB4-binding population of nociceptors, in OIH.Clinically used mu-opioid receptor agonists such as fentanyl can produce hyperalgesia and hyperalgesic priming. We report on an model of nociceptor neuroplasticity mediating this opioid-induced hyperalgesia (OIH) and priming, induced by fentanyl. Using this model, we have found qualitative and quantitative differences between cultured nociceptors from opioid naïve and opioid primed animals, and provide evidence for the important role of nociceptor MOR-mediated calcium signaling and peripheral protein translation, in the weakly IB4-binding population of nociceptors, in OIH. These findings provide information useful for the design of therapeutic strategies to alleviate OIH, a serious adverse event of opioid analgesics.