Adult spinal cord neurogenesis: A regulator of nociception.

Adult spinal cord neurogenesis occurs at low, constant rate under normal conditions and can be amplified by pathologic conditions such as injury or disease. The immature neurons produced through adult neurogenesis have increased excitability and migrate preferentially to the superficial dorsal horn layers responsible for nociceptive signaling. Under normal conditions, this process may be responsible for maintaining a steady-state, but adaptable level of nociceptive sensitivity, thus representing an experience-dependent mechanism of regulation similar to other neurogenic niches. Under pathologic conditions, adult spinal cord neurogenesis is greatly amplified and may therefore account for the observed changes in general spinal cord excitability and nociceptive sensitivity. This mechanism also explains many types of chronic pain present in the absence of injury or disease, which may be the result of impaired neuronal differentiation due to a variety of genetic variations. This suggests the possibility of using promoters of neuronal differentiation for the long-term treatment of the causes of chronic pain, unlike current medication which is palliative and effective only for the duration of treatment. The presence of this spinal cord neurogenic niche may also lead to new approaches in spinal cord regeneration.