Morphometric Evidence That the Total Number of Synapses on Purkinje Neurons of Old F344 Rats Is Reduced After Long-Term Ethanol Treatment and Restored to Control Levels After Recovery

Abstract

Clinical symptoms of alcohol abuse may be confused with symptoms of age-related neuropathologies in human patients. It is important, therefore, to determine the relationships between alcohol abuse and changes in brain structures in well-controlled studies of ageing subjects. Currently there is little well-documented information of this type available. The purpose of this study was to determine whether long-term ethanol treatment during ageing would lead to reductions in synaptic input to cerebellar Purkinje neurons (PN) of old F344 rats that: (1) were more severe than those attributable to ageing alone; (2) might be responsible for an ethanol-related deletion of dendritic segments of PN in old F344 rats shown previously in this laboratory. The total number of synapses per PN dendritic arbor was determined after ethanol treatment of old F344 rats for 40 weeks between 12 and 22 months of age and in similarly treated rats given a subsequent 20-week period of recovery between 22 and 27 months of age. Groups of age-matched rats fed a chow diet and water and rats pair-fed an isocaloric liquid diet lacking ethanol served as controls. The volume of the molecular layer per PN arbor and the numerical density of synapses in the molecular layer was determined from light microscopic preparations of a fixed volume of the cerebellar cortex. Photographic montages of the ultrastructure of the molecular layer of the cerebellum were also prepared from each rat for measurements of synaptic numerical densities. From the volume of the molecular layer per PN arbor and the numerical density of synapses in the molecular layer, the total number of synapses per PN arbor was estimated for each rat. There was a significant reduction in synapses in the old ethanol-treated rats relative to age-matched chow-fed rats. There were also significant interactions between recovery and treatment prior to recovery. During recovery, synaptic numbers in the old, ethanol-treated rats were restored to pre-recovery control levels whereas synaptic numbers in the old, chow-fed rats were significantly reduced during the same period of time. There were no significant diet- or age-related changes in synaptic numbers in the pair-fed control rats during treatment or recovery. The pattern of reduction in synaptic numbers during ethanol treatment and restoration of synaptic numbers during recovery from treatment paralleled the pattern of ethanol-related segment loss and recovery-related segment regrowth noted earlier in PN arbors of old F344 rats, suggesting that reductions in the numbers of synapses and deletion of terminal dendritic segments were causally related in this strain.

Ethanol-related increases in degenerating bodies in the Purkinje neuron dendrites of aging rats

“…Similar to the results of previous studies, chronic ethanol consumption did not result in marked alteration of the general morphology of the molecular layer of the cerebellum (Dlugos and Pentney, 1997;Dlugos 2006 a, b). The molecular layer began superior to the large PN soma at the level of the primary PN dendrite (Fig 1A).…”

“…Tissue preparation is described elsewhere in detail (Dlugos and Pentney, 1997;Dlugos, 2005;Dlugos 2006 a;Dlugos 2006 b). Briefly, at the end of treatment, rats were anesthetized with sodium pentobarbital (100mg/kg) and the brains fixed by perfusion of a bolus of physiological saline followed by 300 ml of 1% glutaraldehyde; 1% paraformaldehyde in 0,1 M phosphate buffer (pH=7.4).…”

“…In an aging Fischer 344 rat model, chronic ethanol consumption for a period of 40 weeks results in regression and degeneration of the very extensive PN dendritic arbor (Pentney andQuackenbush, 1990, 1991;Pentney, 1995;Pentney and Dlugos 2000). PN dendritic regression occurs simultaneously with an accompanying decline in the total number of synapses/ PN (Dlugos and Pentney, 1997). The mechanism behind ethanol-related regression of PN dendrites is unknown but ultrastructural observation of ethanol-related alterations of dendritic organelles may provide cues to cellular components and mechanisms behind the ethanol-related dendritic degeneration that precedes regression.…”

Alterations in synaptic proteins and their encoding mRNAs in prefrontal cortex in schizophrenia: a possible neurochemical basis for ‘hypofrontality’

“…Animal studies have suggested that chronic alcohol treatment may reduce syn- Figure 3 Northern hybridization and densitometric analysis of mRNAs using cDNAs for synaptophysin mRNA, for SNAP-25 mRNA, for GFAP mRNA, and for 28S rRNA in prefrontal (Brodmann's area 10) cortical tissue extracts from schizophrenic and control patients. aptic densities in cerebellum 20,21 and in brainstem nuclei. 22 Such a confounding effect, however, would skew the present data toward lesser, rather than greater, differences between schizophrenic and control populations.…”

Development and Resolution of Brain Lesions Caused by Pyrithiamine- and Dietary-Induced Thiamine Deficiency and Alcohol Exposure in the Alcohol-Preferring Rat: A Longitudinal Magnetic Resonance Imaging and Spectroscopy Study

“…In rodent studies of thiamine deficiency, neurodegenerative evidence has been observed in the frontal cortex and corpus callosum (Savage et al, 2000), cerebellum (eg, Dlugos and Pentney, 1997;Pentney and Dlugos, 2000;Pentney and Quackenbush, 1990;Rintala et al, 1997), and locus coeruleus . Initial MRI studies, conducted at 1.5 T, used thiamine deficiency models of WE (Pentney et al, 1993) and reported increased volume of lateral ventricles followed by normalization with a thiamine-enriched diet (Acara et al, 1995).…”