NMDA RECEPTORS IN MOUSE BARREL CORTEX DURING NORMAL DEVELOPMENT AND FOLLOWING VIBRISSECTOMY

The development of N-methyl-D-aspartate (NMDA) receptors and the effects of vibrissectomy upon [H-3]MK-801 binding were examined in the barrel cortex of mice. Autoradiographic studies showed that initially very low binding of [H-3]MK-801 sharply increased during the second postnatal week reaching the adult level by the end of the third week. Scatchard analysis performed on cortical membrane preparations indicated that this rise of [H-3]MK-801 labelling was due to an increase in the number of binding sites and a decrease of K-d at postnatal day 15 and 28. The interlaminar differences of labelling were registered from postnatal day 8. Changes of interlaminar distribution were found during the second and third postnatal weeks. In adult barrel cortex the highest binding was found in supragranular layers. In layer IV of the cortex, the pattern of binding resembled the pattern of barrels. Unilateral denervation of of vibrissae performed in neonatal and adult mice did not alter the intensity of [H-3]MK-801 labelling or the laminar distribution of binding sites. These results suggest that NMDA receptor binding does not reflect the plastic changes occurring in the barrel cortex.