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o-coupled receptor-mediated presynaptic inhibition at granule cell-interneuron synapses in rat cerebellar cortex
Abstracts P2-b26 Diversity in the Gi/o -coupled receptor-mediated presynaptic inhibition at granule cell-interneuron synapses in rat cerebellar cortex Shin’Ichiro Satake 1,2 , Keiji Imoto 1,2 1
2
National Institute for Physiological Sciences, Okazaki, Japan; ate University for Advanced Studies, Okazaki, Japan
The Gradu-
We previously reported that paired-pulse activation of granule cell (GC) axons caused a transient facilitation not only in the peak amplitude (PPFamp ) but also in the decay time constant (PPFdecay ) of the EPSCs recorded from molecular-layer interneurons (INs). Repetitive activation of GC axons (50 Hz for 400 ms) elicited a presynaptic inhibition of EPSCs derived from different but closely appositional GC pathways converging on the same IN with a significant depression of the PPFdecay . This heterosynaptic inhibition among different GC pathways was suppressed by blocker mixture of group III mGluRs and GABAB Rs. Brief depolarization of INs (0 mV for 2 s) also caused a transient suppression of the GC-IN EPSC depending on a CB1R-mediated retrograde mechanism (namely, DSE). During the DSE, PPFdecay however remained unchanged. These findings suggest that distinct GPCR subtypes play a role to process neuronal information by differentially modifying the properties of vesicular release at the single synapse. doi:10.1016/j.neures.2009.09.727
S145
In the pond snail Lymnaea a tactile or shadow stimulus induces an avoidance behavior, that is part of the whole body withdrawal (WBW) response. We tested at both the behavioral and electrophysiologic level whether WBW was altered in the presence of an ecologically relevant stress. Snails in the predator-exposed group had a significantly more pronounced and longer lasting WBW to the shadow stimulus compared to a control. Since RPeD11 is assumed to be the key interneuron controlling WBW, we focused on the activity of RPeD11. Presenting a shadow stimulus to the pneumostome area evoked an EPSP in RPeD11 in semi-intact preparations (without ocular photoreceptors). This EPSP is monosynaptic and is mediated by dermal photoreceptors in the pneumostome area. That is, the EPSP is present in hi Mg2+ /hi Ca2+ saline while it disappears in Ca2+ free saline. The amplitude and duration of the EPSP are significantly enhanced in the presence of the predator compared to naive preparations. These data strongly suggest that augmentation of sensory input to RPeD11 plays a key role in the enhanced WBW when predator is present. doi:10.1016/j.neures.2009.09.730
P2-b30 Transection of infraorbital nerve induces multiple innervations of lemniscal fibers onto the relay neuron in the somatosensory thalamus Yuichi Takeuchi 1,2,3,4 , Keiji Imoto 2,3 , Mariko Miyata 1 1
Dept. Physiol., Tokyo Women’s Medical University, SOKENDAI, Hayama, Japan; 3 NIPS, Okazaki, Japan; Japan
2
proBDNF-p75NTR
P2-b27 Possible involvement of signaling in LTDrepetition-operated synaptic suppression, a form of long-lasting synaptic plasticity Yoshihiro Egashira 1 , Masami Kojima 2 , Hara Tomoko 2 , Keiko Tominaga-Yoshino 1 , Akihiko Ogura 1 1
Grad. Sch. Frontier Biosci., Osaka University, Osaka, Japan; Japan
2
AIST, Osaka,
Synapse formation and elimination are the cellular bases for memory consolidation. We previously reported that the repeated induction (<3 times) of mGluR-dependent LTD led to the long-lasting reduction in synaptic strength and synapse density in the stable cultures of hippocampal slices. We call this phenomenon LTD-repetitionOperated Synaptic Suppression (LOSS) to distinguish it from conventional single LTD. We have already shown the dependency of LOSS on new protein synthesis in a limited time window. It is recently suggested that the precursor of BDNF (proBDNF) has its own effect in apoptosis and LTD. Thus we examined here the possible involvement of proBDNF and its receptor p75NTR in the induction of LOSS. Application of neutralizing antibody against p75NTR after repeated inductions of LTD prevented the LOSS induction. The results of quantitative analyses on the expression levels of BDNF, proBDNF, TrkB and p75NTR largely in line with the above hypothesis. doi:10.1016/j.neures.2009.09.728
P2-b28 Region-selectivel establishment of repetitive-LTP-induced synaptic enhancement in the cultured hippocampal slice with divided input pathways Yuki Oe Dept. Neurosci., Osaka Univ., Grad. Sch. Frontier Biosci. Suita 565-0871 Osaka, Japan We previously reported that 3 repeated inductions of LTP by means of forskolin (FK; a PKA activator) or glutamate application to the stable cultures of rat hippocampal slice led to a weeks-order enhancement of synaptic strength coupled with synaptogenesis. We named this enhancement RISE to discriminate from single conventional LTP. In order to ascertain that RISE can be evoked locally, we divided the input pathway to the CA1 pyramidal cells with a knife-cut. After 2 global applications of FK, a tetanic stimulation (Tet) was given to one of the pathways. Using a voltagesensitive dye imaging technique we detected a significant enhancement of synaptic response in the region where LTP was induced 3 times (2FK + Tet) but not in the region where LTP was induced twice (2FK). Morphological inspection using Golgi staining is now under way to examine whether local synaptogenesis is accompanied by the enhancement. doi:10.1016/j.neures.2009.09.729
P2-b29 The neuronal substrates of predator induced stress on the shadow response in Lymnaea Hiroshi Sunada, Manabu Sakakibara, Tetsuro Horikoshi Grad. Sch. Biosci, Tokai Univ., Shizuoka, Japan
Tokyo, Japan; 4 JSPS, Tokyo,
Lesion of peripheral sensory nerve induces reorganization of receptive field in the somatosensory thalamus (VPm). However, it is still unknown functional changes of the individual lemniscal synapse, which convey primary somatosensory inputs to VPm, underlie this phenomenon. Our electrophysiological study has previously demonstrated that the thalamic relay neuron becomes to receive a single lemniscal fiber by postnatal days 21 (P21) after developmental synapse elimination in the rodent VPm. Here, we show that the transection of infraorbital nerve at P21 altered the wiring of this synapse. After 1 week from the surgery, multiple steps of lemniscal EPSCs were observed, implying the additional recruitment of lemniscal fibers. Multiply innervated relay neurons occasionally contained silent synapses which were absent in normal young adult mice. These results indicate the lesion-induced rewiring of lemniscal fibers in the VPm. doi:10.1016/j.neures.2009.09.731
P2-b31 Androgens rapidly increased hippocampal dendritic spines and thorns via several kinases Yusuke Hatanaka, Tetsuya Kimoto, Suguru Kawato Dept. Biophys. Life Sci., The Univ. of Tokyo, Tokyo, Japan The hippocampus is a center for learning and memory. Dendritic spines and thorns are postsynaptic structures in hippocampal CA1 and CA3, respectively. It has been reported that the application of androgen have anti-anxietic effects. Therefore, androgen-induced morphological changes of hippocampal spines and thorns has been attracting much attention. Here we demonstrated dihydrotestosterone (DHT) and testosterone (T) rapidly affect the number and morphology of dendritic spines and thorns in rat dorsal hippocampus. The application of 10 nM DHT or T induced rapid increase in the density of spines and thorns within 2 h. While DHT mainly increased large-head spines, T increased small-head spines. These effects was suppressed by blocking MAP kinases, such as ERK1/2 and p38 MAPK. We observed that the androgen-induced thorn-genesis is opposite to estrogen-induced thorndegeneration in CA3. On the other hand, in CA1 region, estrogen had the same effect on spines as androgen. doi:10.1016/j.neures.2009.09.732
P2-b32 The involvement of Raf-kinase inhibitory protein in cerebellar long-term depression Keiko Tanaka-Yamamoto 1,2 , Shinya Kuroda 1 1
Grad. Sch. of Science, The University of Tokyo, Japan;
2
JST, Tokyo, Japan
We have previously demonstrated that a positive feedback loop, including protein kinase C (PKC) and mitogen-activated protein kinase (MAPK), is required for the gradual expression of cerebellar long-term depression (LTD). PKC and MAPK mutually activate in this loop and MAPK-dependent PKC activation is likely mediated by phospholipase A2. However, it is not known how PKC activates MAPK pathways. We tested whether Raf-kinase inhibitory protein (RKIP) is involved in LTD, because RKIP has been reported to regulate MAPK activities via its phosphorylation by PKC in other cells. When recombinant protein of dominant-negative form of RKIP, which is not phosphorylated by PKC, was introduced into Purkinje cells through patch
2
National Institute for Physiological Sciences, Okazaki, Japan; ate University for Advanced Studies, Okazaki, Japan
The Gradu-
We previously reported that paired-pulse activation of granule cell (GC) axons caused a transient facilitation not only in the peak amplitude (PPFamp ) but also in the decay time constant (PPFdecay ) of the EPSCs recorded from molecular-layer interneurons (INs). Repetitive activation of GC axons (50 Hz for 400 ms) elicited a presynaptic inhibition of EPSCs derived from different but closely appositional GC pathways converging on the same IN with a significant depression of the PPFdecay . This heterosynaptic inhibition among different GC pathways was suppressed by blocker mixture of group III mGluRs and GABAB Rs. Brief depolarization of INs (0 mV for 2 s) also caused a transient suppression of the GC-IN EPSC depending on a CB1R-mediated retrograde mechanism (namely, DSE). During the DSE, PPFdecay however remained unchanged. These findings suggest that distinct GPCR subtypes play a role to process neuronal information by differentially modifying the properties of vesicular release at the single synapse. doi:10.1016/j.neures.2009.09.727
S145
In the pond snail Lymnaea a tactile or shadow stimulus induces an avoidance behavior, that is part of the whole body withdrawal (WBW) response. We tested at both the behavioral and electrophysiologic level whether WBW was altered in the presence of an ecologically relevant stress. Snails in the predator-exposed group had a significantly more pronounced and longer lasting WBW to the shadow stimulus compared to a control. Since RPeD11 is assumed to be the key interneuron controlling WBW, we focused on the activity of RPeD11. Presenting a shadow stimulus to the pneumostome area evoked an EPSP in RPeD11 in semi-intact preparations (without ocular photoreceptors). This EPSP is monosynaptic and is mediated by dermal photoreceptors in the pneumostome area. That is, the EPSP is present in hi Mg2+ /hi Ca2+ saline while it disappears in Ca2+ free saline. The amplitude and duration of the EPSP are significantly enhanced in the presence of the predator compared to naive preparations. These data strongly suggest that augmentation of sensory input to RPeD11 plays a key role in the enhanced WBW when predator is present. doi:10.1016/j.neures.2009.09.730
P2-b30 Transection of infraorbital nerve induces multiple innervations of lemniscal fibers onto the relay neuron in the somatosensory thalamus Yuichi Takeuchi 1,2,3,4 , Keiji Imoto 2,3 , Mariko Miyata 1 1
Dept. Physiol., Tokyo Women’s Medical University, SOKENDAI, Hayama, Japan; 3 NIPS, Okazaki, Japan; Japan
2
proBDNF-p75NTR
P2-b27 Possible involvement of signaling in LTDrepetition-operated synaptic suppression, a form of long-lasting synaptic plasticity Yoshihiro Egashira 1 , Masami Kojima 2 , Hara Tomoko 2 , Keiko Tominaga-Yoshino 1 , Akihiko Ogura 1 1
Grad. Sch. Frontier Biosci., Osaka University, Osaka, Japan; Japan
2
AIST, Osaka,
Synapse formation and elimination are the cellular bases for memory consolidation. We previously reported that the repeated induction (<3 times) of mGluR-dependent LTD led to the long-lasting reduction in synaptic strength and synapse density in the stable cultures of hippocampal slices. We call this phenomenon LTD-repetitionOperated Synaptic Suppression (LOSS) to distinguish it from conventional single LTD. We have already shown the dependency of LOSS on new protein synthesis in a limited time window. It is recently suggested that the precursor of BDNF (proBDNF) has its own effect in apoptosis and LTD. Thus we examined here the possible involvement of proBDNF and its receptor p75NTR in the induction of LOSS. Application of neutralizing antibody against p75NTR after repeated inductions of LTD prevented the LOSS induction. The results of quantitative analyses on the expression levels of BDNF, proBDNF, TrkB and p75NTR largely in line with the above hypothesis. doi:10.1016/j.neures.2009.09.728
P2-b28 Region-selectivel establishment of repetitive-LTP-induced synaptic enhancement in the cultured hippocampal slice with divided input pathways Yuki Oe Dept. Neurosci., Osaka Univ., Grad. Sch. Frontier Biosci. Suita 565-0871 Osaka, Japan We previously reported that 3 repeated inductions of LTP by means of forskolin (FK; a PKA activator) or glutamate application to the stable cultures of rat hippocampal slice led to a weeks-order enhancement of synaptic strength coupled with synaptogenesis. We named this enhancement RISE to discriminate from single conventional LTP. In order to ascertain that RISE can be evoked locally, we divided the input pathway to the CA1 pyramidal cells with a knife-cut. After 2 global applications of FK, a tetanic stimulation (Tet) was given to one of the pathways. Using a voltagesensitive dye imaging technique we detected a significant enhancement of synaptic response in the region where LTP was induced 3 times (2FK + Tet) but not in the region where LTP was induced twice (2FK). Morphological inspection using Golgi staining is now under way to examine whether local synaptogenesis is accompanied by the enhancement. doi:10.1016/j.neures.2009.09.729
P2-b29 The neuronal substrates of predator induced stress on the shadow response in Lymnaea Hiroshi Sunada, Manabu Sakakibara, Tetsuro Horikoshi Grad. Sch. Biosci, Tokai Univ., Shizuoka, Japan
Tokyo, Japan; 4 JSPS, Tokyo,
Lesion of peripheral sensory nerve induces reorganization of receptive field in the somatosensory thalamus (VPm). However, it is still unknown functional changes of the individual lemniscal synapse, which convey primary somatosensory inputs to VPm, underlie this phenomenon. Our electrophysiological study has previously demonstrated that the thalamic relay neuron becomes to receive a single lemniscal fiber by postnatal days 21 (P21) after developmental synapse elimination in the rodent VPm. Here, we show that the transection of infraorbital nerve at P21 altered the wiring of this synapse. After 1 week from the surgery, multiple steps of lemniscal EPSCs were observed, implying the additional recruitment of lemniscal fibers. Multiply innervated relay neurons occasionally contained silent synapses which were absent in normal young adult mice. These results indicate the lesion-induced rewiring of lemniscal fibers in the VPm. doi:10.1016/j.neures.2009.09.731
P2-b31 Androgens rapidly increased hippocampal dendritic spines and thorns via several kinases Yusuke Hatanaka, Tetsuya Kimoto, Suguru Kawato Dept. Biophys. Life Sci., The Univ. of Tokyo, Tokyo, Japan The hippocampus is a center for learning and memory. Dendritic spines and thorns are postsynaptic structures in hippocampal CA1 and CA3, respectively. It has been reported that the application of androgen have anti-anxietic effects. Therefore, androgen-induced morphological changes of hippocampal spines and thorns has been attracting much attention. Here we demonstrated dihydrotestosterone (DHT) and testosterone (T) rapidly affect the number and morphology of dendritic spines and thorns in rat dorsal hippocampus. The application of 10 nM DHT or T induced rapid increase in the density of spines and thorns within 2 h. While DHT mainly increased large-head spines, T increased small-head spines. These effects was suppressed by blocking MAP kinases, such as ERK1/2 and p38 MAPK. We observed that the androgen-induced thorn-genesis is opposite to estrogen-induced thorndegeneration in CA3. On the other hand, in CA1 region, estrogen had the same effect on spines as androgen. doi:10.1016/j.neures.2009.09.732
P2-b32 The involvement of Raf-kinase inhibitory protein in cerebellar long-term depression Keiko Tanaka-Yamamoto 1,2 , Shinya Kuroda 1 1
Grad. Sch. of Science, The University of Tokyo, Japan;
2
JST, Tokyo, Japan
We have previously demonstrated that a positive feedback loop, including protein kinase C (PKC) and mitogen-activated protein kinase (MAPK), is required for the gradual expression of cerebellar long-term depression (LTD). PKC and MAPK mutually activate in this loop and MAPK-dependent PKC activation is likely mediated by phospholipase A2. However, it is not known how PKC activates MAPK pathways. We tested whether Raf-kinase inhibitory protein (RKIP) is involved in LTD, because RKIP has been reported to regulate MAPK activities via its phosphorylation by PKC in other cells. When recombinant protein of dominant-negative form of RKIP, which is not phosphorylated by PKC, was introduced into Purkinje cells through patch