Uncoupling protein 2 in primary pain and temperature afferents of the spinal cord.

Uncoupling protein 2 (UCP2) is a mitochondrial protonophore that regulates cellular energy homeostasis. In this study, we explored the expression of UCP2 in the spinal cord. UCP2 was expressed in the substantia gelatinosa and ventral horn of the rodent and primate spinal cord. In all of these areas, UCP2 expression was associated with axons and axon terminals and direct appositions between UCP2-immunoreactive fibers and NMDA glutamate receptors-containing perikarya were frequently detected. All of the UCP2-labeled processes were also immunoreactive for substance P. The expression of UCP2 in primary sensory afferents of the spinal cord suggests that this mitochondrial uncoupler is involved in the mechanism of pain and temperature sensation.