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
Ca. Dlugos et Rj. Pentney, 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, Alcohol and alcoholism, 32(2), 1997, pp. 161-172
Clinical symptoms of alcohol abuse may be confused with symptoms of ag
e-related neuropathologies in human patients. It is important, therefo
re, to determine the relationships between alcohol abuse and changes i
n brain structures in well-controlled studies of ageing subjects. Curr
ently there is little well-documented information of this type availab
le. The purpose of this study was to determine whether long-term ethan
ol treatment during ageing would lead to reductions in synaptic input
to cerebellar Purkinje neurons (PN) of old F344 rats that: (1) were mo
re severe than those attributable to ageing alone; (2) might be respon
sible for an ethanol-related deletion of dendritic segments of PN in o
ld 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 b
etween 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 eth
anol served as controls. The volume of the molecular layer per PN arbo
r and the numerical density of synapses in the molecular layer was det
ermined from light microscopic preparations of a fixed volume of the c
erebellar cortex. Photographic montages of the ultrastructure of the m
olecular layer of the cerebellum were also prepared from each rat for
measurements of synaptic numerical densities. From the volume of the m
olecular layer per PN arbor and the numerical density of synapses in t
he molecular layer, the total number of synapses per PN arbor was esti
mated for each rat. There was a significant reduction in synapses in t
he old ethanol-treated rats relative to age-matched chow-fed rats. The
re were also significant interactions between recovery and treatment p
rior to recovery. During recovery, synaptic numbers in the old, ethano
l-treated rats were restored to pre-recovery control levels whereas sy
naptic numbers in the old, chow-fed rats were significantly reduced du
ring the same period of time. There were no significant diet- or age-r
elated changes in synaptic numbers in the pair-fed control rats during
treatment or recovery. The pattern of reduction in synaptic numbers d
uring ethanol treatment and restoration of synaptic numbers during rec
overy 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 synaps
es and deletion of terminal dendritic segments were causally related i
n this strain.