Morphological evidence of climbing fiber plasticity after long-term alcohol intake.

The morphological effects of long-term alcohol consumption on the climbing fiber terminals of the cerebellum of adult rats were studied in groups of controls and animals fed a 20% aqueous alcohol solution for 1, 3, 6, 12, and 18 months. Following 12 months of alcohol consumption, vacated postsynaptic sites on Purkinje cell spines from large dendrites (the usual postsynaptic targets for climbing fiber terminals) were seen. Concomitantly, an increased number of climbing fiber profiles were observed in the inner third of the molecular layer. Their volumetric density (Vv) was significantly increased in 12 and 18-month alcohol-fed groups. Along with these findings, large numbers of climbing fiber terminals were seen in the outer third of the molecular layer, synapsing with Purkinje cell spines. The data show that climbing fiber terminals under these experimental conditions display structural plastic capabilities which presumably result in functional modifications on the cerebellar circuitry.