Altered Purkinje cell maturation in rats exposed prenatally to ethanol. II. Synaptology.

Pregnant rats of Sprague-Dawley strain were offered a protein- and vitamin-enriched nutritionally balanced liquid ethanol diet, providing 35% of calories as ethanol. Control animals were pair-fed identical liquid diet except that maltose-dextrins were substituted for ethanol. Pups of both ethanol-exposed and pair-fed groups were surrogate-fostered by mothers which received normal rat chow ad libitum. An average of eight pups of each experimental and control group was killed at 0-1, 5, 7, 10, 14, 21, 28, and 42 days. After fixation, their cerebella were bisected in the midvermal plane and one-half embedded in Araldite. Thin sections cut from lobules II/III were stained with uranyl acetate and lead citrate and the synaptology of the Purkinje neurons was studied with the electron microscope in both the experimental and control groups. Impaired climbing fiber maturation was seen in ethanol-exposed pups as evident from the presence of somatic spines--climbing fiber synapses at 14 days postnatally. In the 14-day-old control pups the climbing fiber maturation was complete or nearly complete as evident by their synapses on spines situated on the smooth dendritic branches and by the absence or paucity of climbing fiber--somatic spine synapse. In addition, a reduction in the number of parallel fibers was evident from the increase in Purkinje cell spines per varicosity in the ethanol-exposed pups. We conclude, therefore, a direct or indirect effect of ethanol occurs on climbing fiber maturation and Purkinje cell parallel fiber relationship.