DOI: 10.34945/f56c7w
title: Behaviour and histopathology after simultaneous cortical infusion of PKA and EPAC agonists and rehabilitative forelimb motor training after incomplete cervical spinal cord injury in female rats

description: STUDY PURPOSE: There is a profound lack of regenerative potential following injury to the adult central nervous system. This has been found to be due in part to the decline of cyclic AMP (cAMP) that has been demonstrated to occur as the nervous system develops, as well as the fact that cAMP levels drop further following injury. cAMP is a ubiquitous signalling molecule found throughout the body, and in many different cell types including neurons. It primarily acts through two downstream effectors: Protein Kinase A (PKA) and the Exchange Protein Activation by cAMP (EPAC). Studies investigating the role of these downstream effectors have found that manipulation of these effectors can lead to an increase in neurite extension and even functional recovery after SCI. Recent in vitro work from our lab has demonstrated that simultaneous activation of both PKA and EPAC results in a synergistic increase in neurite extension and neuronal development. The aim of the current study was to investigate the application of agonists for EPAC or for both EPAC and PKA to the motor forelimb cortex innervating the injured corticospinal tract as a means to increase the beneficial effects of rehabilitative motor therapy after cervical SCI in rats. DATA COLLECTED: Female adult Lewis rats from Charles River Laboratories, Canada, weighing 180-220 g were used for this dataset. All rats were pre-trained in the single pellet grasping (SPG) task and received a unilateral dorsal-lateral quadrant (DLQ) spinal cord transection injury at cervical vertebrae level 4 on the side of the dominant paw. Prior to exclusion criteria, n = 13 in the Dual Agonist group, n = 15 in the EPAC Agonist group, n = 23 in control. Lesion size analysis, SPG functional scores, High Speed grasp motion analysis score, Von Frey data, MEP Latency, Count of Significant bins in collateral CST fiber density heatmapping data. Pharmacological compounds used in this study were: - 8-CPT-2'-Me-cAMP (EPAC Agonist) - 6-BnZ-cAMP (PKA Agonist) Pharmacological compounds were dissolved in sterile phosphate buffered saline, loaded into Alzet osmotic mini-pumps (model 2002) to a final in pump concentration of 300 micromolar per compound, and left in an incubator overnight at 37 degrees celsius to prime the pumps to start drug flow. Pumps were installed in the animals immediately following SCI and connected to an Alzet brain infusion kit (No. 2) that was modified to shorten the cannula needle down to 1.5 millimeters. When placed over the skull of the animal, this would result in a cortical penetration depth of approximately 0.5 millimeters. The infusion kits were installed over the motor forelimb cortex innervating the injured side of the spinal cord. Pumps remained in place for two weeks to allow for the pumps to fully release their contents. Control animals received pumps filled with saline. Corticospinal tract tracing was performed using Biotin Dextran Amine (BDA). A 10% BDA solution is made using sterile phosphate buffer. Each animal received 3 injections of 1 microliter of this solution in the cortical area surrounding the motor forelimb cortex innervating the injured CST (approximately 1.5 mm rostral and 1.5 mm lateral to bregma) DATA USAGE NOTES: Prolonged cortical injusion of agonists for EPAC or for both EPAC and PKA did not result in increases in functional motor recovery or CST plasticity using this methodology