Developmental regulation of PSD-95 and nNOS expression in lumbar spinal cord of rats.

Postsynaptic density (PSD)-95 is originally isolated from glutamatergic synapse where it serves as a physical tether to allow neuronal nitric oxide synthase (nNOS) signaling by N-methyl-D-aspartate receptor (NMDAR) activity. Considering the physiological importance of glutamate receptor and nitric oxide (NO) during development, we examined the spatiotemporal expression of PSD-95 and nNOS in the lumbar spinal cord at a postnatal stage. Temporally, both gene and protein levels of them gradually increased with age after birth, peaked at the postnatal day 14 (P14), and then decreased to an adult level. In addition, the enhanced coimmunoprecipitations between PSD-95 and nNOS were detected in developing spinal cord. Spatially, PSD-95 staining codistributed with nNOS in NeuN-positive motor neurons and sensory neurons at P14. These findings indicate that PSD-95 and nNOS might collectively participate in spinal cord development.