Upregulation of Protein Kinase C Gamma in Spinal Cord after Formalin Intracolonic Injection

Visceral pain remains one of the most commonly observed clinical symptoms, and yet, it continues to represent a large unmet therapeutic demand. Work from our lab and others have aimed to describe potential mechanisms underlying the pathophysiology of visceral pain and have identified protein kinase C gamma (PKC γ) as an important molecular target, as it undergoes prominent membrane translocation in visceral pain and directly affects many pain signaling pathways. In this study, we continued our investigation of PKC γ modulation in visceral pain and measured PKC γ expression in the spinal cord at 30, 60, and 120 min following visceral pain that was induced by intracolonic injection of formalin. PKC γ mRNA was significantly increased at 60 min following formalin injection, but not at 30 or 120 min following injection, as detected by reverse transcriptase polymerase chain reaction (RT-PCR). Western blot analysis and immunocytochemistry confirmed the up-regulation of PKC γ protein expression at 60 min following formalin injection. Furthermore, immunocytochemistry also confirmed the localization of PKC γ positive neurons to the superficial layers of the spinal cord dorsal horn, where primary afferent terminals transmitting pain information are received. Taken together, our results implicate an important role for PKC γ in the development of visceral pain.