A Study on the Role of N-Methyl-D-Aspartate Receptors in the Rat Visual Cortex

The amino acid L-glutamate is a major excitatory neurotransmitter in the central nervous system of vertebrates.¹ NMDA (N-methyl-d-aspartate) is one of the L-glutamate receptor subtypes.² During a critical period of early postnatal development, the viusal cortex is susceptible to experience-dependant modification of neuronal respones.³ Recently, the activation of NMDA receptors has been supposed as a prerequisite for the induction of such modification.³ We therefore investigated developmental changes of NMDA receptors in the rat visual cortex and questioned whether they could be related to the visual development. We assessed the density of [³H]-NMDA receptor in the visual cortex of normally reared rate (Group I) and visually deprived rats (Group II) using quantitative autoradiography.⁴ The density of [³H]-NMDA receptor was significantly lower in Group II than in group I during the early postnatal period, and increased rapidly by postnatal 1 week and, decreased after postnatal 5 weeks. These results suggested that NMDA receptors may play a role in neuronal development in the visual cortex during the early postnatal period.