Effects of Prenatal Ethanol Exposure on Dendritic Spines of Layer V Pyramidal Neurons in the Somatosensory Cortex of the Rat

The number of dendritic spines on consecutive segments from the cell body along the 400-600 micron proximal region of the apical dendrites of layer V pyramidal neurons, impregnated with the rapid Golgi method, in the somatosensory cortex was counted in ethanol-treated rats during gestation (25% ethanol in drinking water representing 30-35% of the total caloric intake) and in age-matched controls at postnatal ages 4, 15, 30 and 90 days. Although the mean values were lower in ethanol-treated rats than in controls during the first fortnight of postnatal life, significantly lower numbers of spines were observed only in the 15-day-old rat (Student's t-test, P less than 0.01-0.001). Spines with long, thin pedicles were characteristically encountered in ethanol-treated and controls aged 4 days; this sort of spine also predominated in ethanol-treated rats aged 15 days, but not in age-matched controls. The decrease in number and the abnormal morphology of spines was no longer present in ethanol-treated rats aged 30 and 90 days. These data suggest that impaired maturation of dendritic spines on cortical pyramidal cells, followed by recovery of the altered parameters at the end of the first postnatal month, occurs in the offspring of ethanol-treated rats during gestation.