Comparative LTP profiles in the stratum oriens
(n = 6, left-hand graphs) and stratum radiatum
(n = 9, right-hand graphs) in 4-month-
(A Top) and 10-month-old (B
Middle) wild-type and mutant animals induced by 100 Hz for
1 s tetanus. LTP is selectively impaired in the stratum oriens,
and the magnitude of the deficit is increased with age.
(C) The bar graphs (Bottom) illustrate
LTP saturation profiles in the stratum oriens and radiatum of the
hippocampal CA1 region in a separate group of 10-month-old mutant and
wild-type mice (n = 4). These profiles were
generated by delivering a series of tetani, each comprising 100 Hz for
1 s, each tetanus separated from the next by a 30-min interval. No
significant differences were noted in the LTP saturation profiles in
the stratum radiatum (P > 0.05). In contrast, the
magnitude of LTP induced by each consecutive tetanus in the stratum
oriens of mutant animals was smaller than that observed in wild-type
mice (t test, *, P < 0.05,
**, P < 0.01).