Developmental regulation of N-methyl-D-aspartate- and kainate-type glutamate receptor expression in the rat spinal cord

Spinal motor neurons undergo experience-dependent development during a crit ical period in early postnatal life. It has been suggested that the reperto ire of glutamate receptor subunits differs between young and mature motor n eurons and contributes to this activity-dependent development. In the prese nt study we examined the expression patterns Of N-methyl-D-aspartate- and k ainate-type glutamate receptor subunits during the postnatal maturation of the spinal cord. Young motor neurons express much higher levels of the N-me thyl-D-aspartate receptor subunit NR I than do adult motor neurons. Althoug h there are eight potential splice variants of NR1, only a subgroup is expr essed by motor neurons. With respect to NR2 receptor subunits, young motor neurons express NR2A and C, while adult motor neurons express only NR2A. Yo ung motor neurons express kainate receptor subunits GluR5, 6 and KA2 but we are unable to detect these or any other kainate receptor subunits in the a dult spinal cord. Other spinal cord regions display a distinct pattern of d evelopmental regulation of N-methyl-D-aspartate and kainate receptor subuni t expression in comparison to motor neurons. Our findings indicate a precise spatio-temporal regulation of individual su bunit expression in the developing spinal cord. Specific combinations of su bunits in developing neurons influence their excitable properties and could participate in the emergence of adult neuronal form and function. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.