Adenosine A _2A analogue reduces long-term neurologic injury after blunt spinal trauma

ATL-146e is an adenosine A _2A agonist that has recently been demonstrated to improve neurological outcome in spinal cord injury in animals. In the current study, we extended the treatment paradigm and tested neurobehavioral functioning out to 1 week after injury to assess if early neurological improvement is sustained long term by an adenosine analogue. New Zealand White rabbits (3.0-3.5 kg) sustained mid-thoracic blunt spinal cord injury using a weight-drop model (10 g weight dropped from 6 cm directly onto dura). Animals received either (1) 3 h iv infusion of saline carrier (Trauma, N = 21); (2) 3 h iv infusion of 0.06 μg/kg/min ATL-146e followed by intraperitoneal bolus of 10.8 μg/kg ATL-146e at 3 h postinjury (ATL, N = 14); or (3) 3 h iv infusion of 0.06 μg/kg/min ATL-146e followed by intraperitoneal bolus injection of 10.8 μg/kg ATL-146e at 3, 12, and 24 h postinjury (ATL-PLUS, N = 11). Fourteen animals underwent sham injury. Hemodynamic parameters were monitored and hind limb motor functioning was assessed by Tarlov scores (0 = paralyzed to 5 = normal hop) for 7 days after injury. ATL-146e significantly improved Tarlov scores of ATL-146e groups compared with saline-treated controls (P < 0.01 12, 24, 36, and 48 h). Control animals, severely neurologically impaired at 48 h (Tarlov 1.61 ± 0.35), were euthanized early due to ethical concerns, thus not permitting later statistical comparisons. Early neurological improvements in both ATL-146e-treated groups were sustained longer term (7 day mean Tarlov, SHAM 4.9 ± 0.30, ATL 5.0 ± 0, ATL-PLUS 4.25 ± 0.31). ATL-146e given immediately after blunt spinal cord trauma significantly improves neurological outcome, which is sustained through 7 days. Early adenosine A2A receptor agonism may be critical since additional IP administration afforded no further neurological improvement. The current data further support the potential clinical utility of adenosine A _2A agonists in the treatment of spinal cord injury.