Effects of prenatal and early postnatal ethanol exposure on [3H]MK-801 binding in rat cortex and hippocampus

The effects of prenatal and/or early postnatal exposure to ethanol at high concentrations on N-methyl-D-aspartate (NMDA) receptor number and functioning in the weanling rat were examined. The binge-like exposure protocol was used in an animal model of acute ethanol effects at two critical periods of development. [3H]MK-801 binding parameters for the internal channel phencyclidine site were assessed in the presence of 10 microM glutamate and 10 microM glycine activation. Four treatment groups were included: (1) animals exposed to ethanol both prenatal and postnatal; (2) animals exposed only prenatal; (3) animals exposed early postnatal only; and (4) control animals with no exposure to ethanol. The results of the [3H]MK-801 binding experiments showed that both prenatal and postnatal exposure to ethanol resulted in a significant decrease in the density of NMDA receptors. In addition, data indicated an apparent increase in the percentage of high-affinity state (open channel state) relative to low-affinity state (close channel state) receptors in the ethanol-treated groups. These results show that both prenatal and postnatal ethanol exposure decrease NMDA receptor density in the cortex and hippocampus. The findings are consistent with previous observations by our laboratory and others that NMDA-mediated calcium influx is reduced in these regions, as well as in whole brain by prenatal ethanol exposure. It is suggested that after ethanol exposure, the remaining functional NMDA receptors might have altered sensitivity to coagonist activation with an increased probability of channel opening.