This suggested that
the proportion of such axon terminals might be increased in
learning-impaired aged rats, resulting in a loss of synaptic
junctions. Another possibility could be that multiple-synapse
boutons establishing separate synaptic contacts with two
or more spines in the CA1 stratum radiatum of adult rats
[64,71] might be transformed into single-synapse boutons in
aged rats with impaired spatial learning. This would lead to
a reduction in the number of synapses, but not of axon terminals.
Our data derived from synapse quantification at the
electron microscopic level do not support the above possibilities.
The findings reported here definitively demonstrate,
for the first time, that neither age-related deficits in spatial
learning nor advanced chronological age is associated with
a loss of axospinous synapses from the rat CA1 stratum
radiatum.