Ks. Jun et al., ENHANCED HIPPOCAMPAL CA1 LTP BUT NORMAL SPATIAL-LEARNING IN INOSITOL 1,4,5-TRISPHOSPHATE 3-KINASE(A)-DEFICIENT MICE, Learning & memory, 5(4-5), 1998, pp. 317-330
To define the physiological role of IP(3)3-kinase(A) in vivo, we have
generated a mouse strain with a null mutation of the IP(3)3-kinase(A)
locus by gene targeting. Homozygous mutant mice were fully viable, fer
tile, apparently normal, and did not show any morphological anomaly in
brain sections. In the mutant brain, the IP4 level was significantly
decreased whereas the IP3 level did not change, demonstrating a major
role of IP(3)3-kinase(A) in the generation of IP4. Nevertheless, no si
gnificant difference was detected in the hippocampal neuronal cells of
the wild-type and the mutant mice in the kinetics of Ca2+ regulation
after glutamate stimulation. Electrophysiological analyses carried out
in hippocampal slices showed that the mutation significantly enhanced
the LTP in the hippocampal CA1 region, but had no effect on the LTP i
n dentate gyrus (DG). No difference was noted, however, between the mu
tant and the wild-type mice in the Morris water maze task. Our results
indicate that IP(3)3-kinase(A) may play an important role in the regu
lation of LTP in hippocampal CA1 region through the generation of IP4,
but the enhanced LTP in the hippocampal CA1 does not affect spatial l
earning and memory.