PI3-kinases (PI3Ks) participate in nociception within spinal cord, dorsal root ganglion (DRG) and peripheral nerves. To extend our knowledge, we immunohistochemically stained for each of the four Class I PI3K isoforms along with several cell specific markers within lumbar spinal cord, DRG and sciatic nerve of naïve rats. Intrathecal and intraplantar isoform specific antagonists were given as pre-treatments before intraplantar carrageenan; pain behavior was then assessed over time. The α-isoform was localized to central terminals of primary afferent fibers in spinal cord laminae IIi-IV as well as to neurons in ventral horn and DRG. The PI3Kβ isoform was the only Class I isoform seen in dorsal horn neurons, it was also observed in DRG, Schwann cells and axonal paranodes. The δ-isoform was found in spinal cord white matter oligodendrocytes and radial astrocytes, while the γ-isoform was seen in a subpopulation of IB4-positive DRG neurons. No isoform co-localized with microglial markers or satellite cells in naïve tissue. Only the PI3Kβ antagonist, but none of the other antagonists, had anti-allodynic effects when administered intrathecally; coincident with reduced pain behavior, this agent completely blocked paw carrageenan-induced dorsal horn 2-amino-3-(3-hydroxy-5-methylisoxazol- 4-yl) propanoic acid (AMPA) receptor trafficking to plasma membranes. Intraplantar administration of the γ-antagonist prominently reduced pain behavior. These data suggest that each isoform displays specificity with regard to neuronal type as well as to specific tissues. Furthermore, each PI3K isoform has a unique role in development of nociception and tissue inflammation.