Intracellular calcium ion dynamics involved in long-term potentiation in hippocampal CA1 neurons in mice lacking the IP3 type 1 receptor.
In the present study, mice lacking the type 1 inositol-1,4,5-trisphosphate receptor (IP(3)R) were used to study the role of type 1 IP(3)Rs in the induction of long-term potentiation (LTP) in hippocampal CA1 neurons. The magnitude of the LTP induced by high frequency stimulation (HFS) consisting of 20 pulses at 30Hz in mice lacking type 1 IP(3)Rs was significantly larger than that in wild-type mice in terms of the field excitatory postsynaptic potential and population spike. By measuring changes in the intracellular Ca(2+) concentration ([Ca(2+)](i)) in CA1 pyramidal neurons using fluorometry, we found that the decay time of the transient increase in the [Ca(2+)](i) evoked by the HFS in mutant mice was significantly longer than that in wild-type mice, whereas the [Ca(2+)](i) at rest and the magnitude of the [Ca(2+)](i) increases caused by the HFS were no different from those in wild-type mice. In slices from the mutant mice, paired-pulse stimulation (PPS) delivered at an interval of 10ms resulted in significantly weaker paired-pulse inhibition (PPI) than in wild-type mice, suggesting that lack of type 1 IP(3)Rs reduces the PPI induced by PPS in the CA1 region. These results indicate that a lack of type 1 IP(3)Rs causes a slower decay of the transient [Ca(2+)](i) in CA1 pyramidal neurons and attenuates the activity of inhibitory interneurons, resulting in enhancement of LTP induction.
Yoshioka
Masatomo
M
Department of Physiology, Yamagata University School of Medicine, 2-2-2 Iida-Nishi, Yamagata 990-9585, Japan.
Yamazaki
Yoshihiko
Y
Fujii
Satoshi
S
Kaneko
Kenya
K
Kato
Hiroshi
H
Mikoshiba
Katsuhiko
K
D000818:Animals; D000831:Animals, Newborn; D001703:Biophysics; D056547:CA1 Region, Hippocampal / Q000166:cytology*; D002118:Calcium / Q000378:metabolism*; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000172:deficiency*; D007424:Intracellular Fluid / Q000378:metabolism*; D017774:Long-Term Potentiation / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism*; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology
D018691:Excitatory Amino Acid Antagonists; D053496:Inositol 1,4,5-Trisphosphate Receptors; C056639:2-amino-5-phosphopentanoic acid; D014633:Valine; D002118:Calcium