Exploring the nature of spinal cord plasticity: Neurobiological mechanisms and implications for recovery after injury
Prior research has shown that pain (nociceptive) circuits within the spinal cord are affected by environmental relations and support some simple forms of learning (e.g., sensitization, instrumental conditioning). Further, learning can induce a modification in the capacity for learning (a form of metaplasticity); controllable stimulation enables learning through a process that depends upon brain derived neurotrophic factor (BDNF) while uncontrollable stimulation induces a lasting learning impairment that has been linked to the development of central sensitization and the cytokine tumor necrosis factor (TNF). I review data that show temporal predictability also affects spinal function by engaging an internal oscillator. Spinal injury disrupts descending serotonergic fibers that appear to quell nociceptive sensitization. This process is related to a change in the co-transporters that regulate spinal GABA function. It is also shown that nociceptive stimulation impairs recovery after a contusion injury. This effect is related to increased cell death and alterations in BDNF/TNF. Potential therapeutic treatments will be discussed.