Long-term potentiation and long-term depression in hippocampal CA1 neurons of mice lacking the IP(3) type 1 receptor.
To investigate the role in synaptic plasticity of Ca(2+) released from intracellular Ca(2+) stores, mice lacking the inositol 1,4,5-trisphosphate type 1 receptor were developed and the physiological properties, long-term potentiation, and long-term depression of their hippocampal CA1 neurons were examined. There were no significant differences in basic synaptic functions, such as membrane properties and the input/output relationship, between homozygote mutant and wild-type mice. Enhanced paired-pulse facilitation at interpulse intervals of less than 60 ms and enhanced post-tetanic potentiation were observed in the mutant mice, suggesting that the presynaptic mechanism was altered by the absence of the inositol 1,4,5-trisphosphate type 1 receptor. Long-term potentiation in the field-excitatory postsynaptic potentials induced by tetanus (100 Hz, 1 s) and the excitatory postsynaptic currents induced by paired stimulation in hippocampal CA1 pyramidal neurons under whole-cell clamp conditions were significantly greater in mutant mice than in wild-type mice. Homosynaptic long-term depression of CA1 synaptic responses induced by low-frequency stimulation (1 Hz, 500 pulses) was not significantly different, but heterosynaptic depression of the non-associated pathway induced by tetanus was blocked in the mutant mice. Both long-term potentiation and long-term depression in mutant mice were completely dependent on N-methyl-D-aspartate receptor activity. To rule out the possibility of an effect compensating for the lack of the inositol 1,4,5-trisphosphate type 1 receptor occurring during development, an anti-inositol 1,4,5-trisphosphate type 1 receptor monoclonal antibody that blocks receptor function was diffused into the wild-type cell through a patch pipette, and the effect of acute block of inositol 1,4,5-trisphosphate type 1 receptor on long-term potentiation was examined. Significant enhancement of long-term potentiation was observed compared with after control immunoglobulin G injection, suggesting that developmental redundancy was not responsible for the increase in long-term potentiation amplitude observed in the mutant mouse. The properties of channels that could be involved in long-term potentiation induction were examined using whole-cell recording. N-methyl-D-aspartate currents were significantly larger in mutant mice than in wild-type mice only between holding potentials of -60 and -80 mV. We conclude that inositol 1,4,5-trisphosphate type 1 receptor activity is not essential for the induction of synaptic plasticity in hippocampal CA1 neurons, but appears to negatively regulate long-term potentiation induction by mild modulation of channel activities.
Nagase
T
T
Department of Physiology, Yamagata University School of Medicine, 990-9585, Yamagata, Japan.
Ito
K I
KI
Kato
K
K
Kaneko
K
K
Kohda
K
K
Matsumoto
M
M
Hoshino
A
A
Inoue
T
T
Fujii
S
S
Kato
H
H
Mikoshiba
K
K
D000200:Action Potentials / Q000235:genetics; D000818:Animals; D015220:Calcium Channels / Q000172:deficiency* / Q000235:genetics; D020013:Calcium Signaling / Q000235:genetics*; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000235:genetics; D006624:Hippocampus / Q000378:metabolism* / Q000503:physiopathology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D017774:Long-Term Potentiation / Q000235:genetics*; D036881:Long-Term Synaptic Depression / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D017966:Pyramidal Cells / Q000378:metabolism* / Q000503:physiopathology; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency* / Q000235:genetics; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D009435:Synaptic Transmission / Q000235:genetics
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D016194:Receptors, N-Methyl-D-Aspartate