No abstract

Male rats were exposed daily to ethanol vapour from 3 days of age, and their brains were examined at 7, 14, 21, 56 and 76 days postnatally. Control animals were examined at each age, and ethanol-rehabilitated animals were examined at 56 and 76 days postnatally. Tissue from the parietal cortex of each animal stained with osmium tetroxide and with ethanolic-phosphotungstic acid (E-PTA) was analyzed by qualitative ultra-structural techniques. The ethanol flow rate in the incubation chamber was adjusted to maintain the blood ethanol level as close as possible to 0.1 g/100 ml. Ethanol-treated rats weighed less than ethanol-rehabilitated animals at days 56 and 76. At day 7 synapses were formed between axons and dendritic growth cones, dendritic shafts and filopodia in control and ethanol-treated tissue. At days 14 and 21 well-developed axodendritic and axospinous synapses were evident in both groups. The neuropil of 56- and 76-day-old material was similar in the control and treatment groups, except that there was an enlargement of dendritic profiles in the 56-day-old ethanol-treated material. Perforated synapses were most common in 56-day-old ethanol-treated material, with degenerating synapses most common in 56-day-old (and to a lesser extent 76-day-old) ethanol-rehabilitated material. No obvious differences were detected between any of the groups of the E-PTA-stained material. The presence of degenerating and perforated synapses suggests that synaptic remodelling is occurring, and this may be a means of adapting synaptic mechanisms to the functional demands imposed by ethanol.

Male rats were exposed to ethanol vapour daily from 3 days of age, and their brains were examined at 7, 14, 21, 56 and 76 days postnatally. Control animals were examined at each age, with ethanol-rehabilitated animals being examined at 56 and 76 postnatal days. Tissue, stained with osmium tetroxide and with ethanolic-phosphotungstic acid, from the parietal cortex of each animal was analyzed by quantitative ultrastructural techniques. Most of the statistically significant findings occurred at days 56 and 76. When compared with controls, ethanol-treated material at 56 days was characterized by a decrease in the number of synapses which were larger and more spherical, with a greater number of synaptic vesicles and a decrease in dense projections. At 76 days there was an increase in the percentage of axospinous-symmetrical terminals in the ethanol-treated population. In ethanol-rehabilitated tissue at 56 days the synaptic terminals were relatively immature, and were smaller, with a reduced number of synaptic vesicles coupled with an increase in large cisternae and with more positively curved junctions. By 76 days this material was practically indistinguishable from control tissue. It is proposed that at 56 days of age synaptic remodelling is under way in the ethanol-treated material, whereas following rehabilitation the terminals are relatively immature and appear to be actively functioning. Low to moderate levels of ethanol administered postnatally have a limited effect on synaptic maturation.