Spinal Noradrenergic Alpha-2 Receptors Mediate the Antinociceptive Effects of Therapeutic Intraspinal Microstimulation

This study investigates the role of noradrenergic signaling in the antinociceptive effects of intraspinal microstimulation intended to restore movement after spinal cord injury. Two rat cohorts, intact and with chronic spinal cord injury, underwent intraspinal microstimulation (ISMS), and the multiunit neuronal response to peripheral noxious stimulation was examined at the spinal cord level. The observed effects were compared with those after blocking alpha-2 adrenergic receptors using RX821002. SCI heightened the nociceptive response to pinch stimulation, but ISMS exhibited clear antinociceptive effects in both intact and injured groups. These effects were nullified by blocking alpha-2 receptors, highlighting their involvement in the depression of nociceptive processing induced by ISMS.