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288 Abstracts / Neuroscience R

2-k21 Mechanisms for regulation of synaptic plasticitynd memory formation by RARasanori Nomoto 1,2 , Yohei Takeda 1, Koji Mitsuda 1, Satoshi

ida 1,2

Department of Bioscience, Tokyo University of Agriculture, Tokyo, JapanCREST, JST, Tokyo, Japan

etinoic acid (RA), Vitamin A metabolite, functions as a specific ligand foretinoic acid receptors (RARs) and regulates various biological phenomenahrough transcriptional regulation. RARs highly and ubiquitously express inrain. Previous studies showed that RA-deficient mice and RARs-knockoutice exhibit impairments of hippocampal LTP and spatial memory, sug-

esting that RARs may play an important role in hippocampal synapticlasticity and memory. However, molecular mechanisms in which RARs reg-late synaptic plasticity and memory remain unclear. To ask this question, weave examined effects of loss-of-functions of RARs on memory and LTP byenerating and analyzing conditional mutant mice that enable to regulateorebrain-specific overexpression of dominant negative RARalpha mutantalpha-402) lacking C-terminal region of RARalpha (aa 403–462). Our recenttudies have shown that these mutant mice displayed impairments of hip-ocampal AMPA receptor-mediated excitatory postsynaptic potentials, LTPnd memory formation. To understand mechanisms of these impairmentst the molecular level, we performed biochemical analyses. Our expres-ion analyses revealed that inducible overexpression of alpha-402 led toecreases in expression of GluR1 and PSD-95 in hippocampus. These resultsuggest that RARs regulate memory formation and LTP via changing inxpression of synaptic plasticity-related genes. We are also analyzing expres-ion levels of RAR target genes in these mutant mice. To further understandechanisms in which RARalpha regulates learning and memory and LTP,e generated mutant mice expressing another dominant negative RARal-ha mutant (alpha-391) that displays an additional truncation containing auclear export signal compared to alpha-402 mutant. We are now perform-

ng biochemical, electrophysiological and behavioral analyses using theseutant mice.

oi:10.1016/j.neures.2010.07.1278

2-k22 Analysis of brain regions activated followingetrieval of remote fear memory in passive avoidance taskue Zhang 1,2 , Hotaka Fukushima 1,2, Satoshi Kida 1,2

Department Bio., Tokyo University of Agriculture 2 CREST

o generate long-term memory (LTM), short-term memory is stabilizedhrough memory consolidation. Previous studies have shown that retrievalf LTM is dependent on hippocampal function when memory is recent (day-ld), whereas retrieval of LTM becomes hippocampus-independent whenemory is remote (month-old). Our previous study using passive avoid-

nce task has shown that memory is strengthened by memory reactivation.n this study, we tried to characterize recent memory and remote mem-ry after reactivation using passive avoidance task. Consistent with ourrevious finding, we observed that re-exposure to the light box 24 h afterraining led to an enhancement of fear memory. In contrast, re-exposure tohe light box 3 weeks after training did not lead to this enhancement. Tonderstand mechanisms by which memory is enhanced after reactivationhen memory is recent but not remote, we examined brain regions acti-

ated following reactivation of recent and remote memory by analyzing thexpression level of c-fos, a marker of activity-dependent transcription, usingmmunohistochemistry. Consistent with our previous findings, increases in-fos expression were observed in medial prefrontal cortex (mPFC), amyg-ala (Amy) and hippocampus (HP) following retrieval of recent fear memory.

n contrast, we observed increases in c-fos expression in mPFC and ante-ior cingulate cortex (ACC) but not in HP and Amy when memory wasemote. From these findings, we suggest that activations of mPFC/ACC and/ornactivations of HP/Amy inhibit enhancement of remote fear memory afteretrieval.

oi:10.1016/j.neures.2010.07.1279

2-k23 Roles of CREB and BDNF in short- and long-termemory

1,2 1 1,2

otaka Fukushima , Takuya Mukawa , Satoshi KidaDep. of Bioscience, Tokyo University of Agriculture 2 CREST, JST

revious findings that loss-of-function of CREB leads to an impairment ofong-term memory (LTM) suggest that CREB positively regulates memoryormation. To examine whether gain-of-function of CREB enhances memory

ch 68S (2010) e223–e334

formation, we have generated and analyzed transgenic mice expressing adominant active CREB mutant (Y134F or DIEDML) in forebrain. These trans-genic mice displayed enhancements of ST- and LT- social recognition andfear memories. We also found up-regulation of hippocampal BDNF in thesetransgenic mice. Interestingly, transgenic lines displaying higher expressionof BDNF exhibited enhancement of shorter-term memory. In this study, tounderstand roles of up-regulated BDNF in STM and LTM, we examined effectsof microinfusion of BDNF or BDNF inhibitor (trkB blocker; K252a) on socialrecognition memory into hippocampus. Consistent with previous observa-tions, microinfusion of BDNF or BDNF inhibitor enhanced and impaired STM,respectively, in WT mice. Interestingly, infusion of low-dose -BDNF, thatdid not affect STM in WT mice, enhanced 30 min-STM in Y134F-line C micethat display up-regulated BDNF but normal 30 min-STM, suggesting that up-regulated BDNF in these mutant mice contributed to enhancement of STM.Furthermore, infusion of higher-dose-K252a is required to impair 2 h-STM inDIEDML mice compared to WT mice. Finally, we asked whether up-regulatedBDNF contributes to enhancement of LTM. Microinfusion of BDNF furtherenhanced LTM in Y134F-line A mice that display normal BDNF level butenhanced LTM, suggesting that up-regulated BDNF and CREB activity coop-eratively enhances LTM-formation. Our findings suggest that CREB positivelyregulates memory consolidation and moreover, affect the degree in abilityin memory performance through expression regulation of BDNF.

doi:10.1016/j.neures.2010.07.1280

P2-k24 Regulation of memory formation by retinoic acidreceptorsYohei Takeda 1 , Masanori Nomoto 1,2, Hatsune Enomoto 1, TesuChoi 1, Shusaku Uchida 1, Takahisa Miyao 1, Satoshi Kida 1,2

1 Department of Bioscience, Tokyo University of Agriculture, Tokyo, Japan2 CREST, Tokyo, Japan

Retinoic acid (RA), Vitamin A metabolite, functions as a specific ligand forretinoic acid receptors (RARs) and regulates various biological phenomenathrough transcriptional regulation. RARs highly and ubiquitously express inbrain. Previous studies have shown that RA-deficient mice and RARs knock-out mice exhibit impairments of LTP and spatial memory, suggesting thatRARs may play an important role in learning and memory. To further clar-ify the roles of RARs in learning and memory, we generated conditionalmutant mice that enable to regulate forebrain-specific expression of dom-inant negative (dn) mutant of RAR� using tetracycline system (Mayford etal., 1996). We first observed that overexpression of dnRAR� leads to impair-ments of formation of social recognition and spatial memories, suggestingthat RARs are required for memory formation. We further examined effectsof loss-of-RARs-function on memory formation using social recognition task.dnRAR� mutant mice displayed an impairment of 2 h-short-term memory(STM) when mice were exposed to a juvenile mouse for 1.5 min. However,stronger training condition (exposure for 3 min) rescued this deficit of STM.Furthermore, although these mutant mice displayed an impairment of 24 hlong-term memory (LTM) when mice were exposed to a juvenile mousefor 3 min, spaced trainings (exposure for 3 min twice) by 10 min, 1 or 2 hinterval rescued this impairment of LTM. Taken together with our previousfinding that dnRAR� mutant mice displayed an impairment of LTP in hip-pocampal CA1 neuron after weak conditioning stimulation but not strongconditioning stimulation, a nice correlation between memory performanceand hippocampal LTP in dnRAR� mutant mice suggests that RARs signalingpathway regulates memory formation via the changes in neuronal plasticity.

doi:10.1016/j.neures.2010.07.1281

P2-k25 Reward prediction error coding in striatal neuronsKei Oyama 1 , Istvan Hernadi 2, Toshio Iijima 1, Ken-IchiroTsutsui 1

1 Division of Systems Neuroscience, Tohoku University Graduate School ofLife Sciences 2 Department of Exp. Zool. and Neurobiol., University of Pécs,Pécs, Hungary

Midbrain dopamine neurons are known to code reward prediction error(RPE), the difference between expected and received reward. The RPE sig-nal carried by dopamine is considered to be working as a teaching signal inreward-based learning, as it modifies the strength of synaptic connectivity in

the target neurons. A fundamental interest in current neuroscience concernsthe neural origin of dopamine RPE signals. So far little is known whethermedium spiny projection neurons, which are the vast majority of striatalneurons, are involved in RPE coding. The purpose of this study was to exam-ine whether RPE signals are coded in the striatum. We recorded single-unit

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Abstracts / Neuroscience R

ctivity in the striatum of rats that had been conditioned in a probabilisticavlovian conditioning task, in which different sensory stimuli (auditory tonetimuli) are associated with different reward probabilities (0%, 25%, 50%, 75%nd 100%). We found that a group of striatal neurons showed a clear paramet-ic RPE coding similar to that of dopamine neurons, that is, the CS responses strongest when the CS indicates 100% reward probability and gradually

eakens as the indicated reward probability decreases, whereas the rewardesponse is weakest when the reward is totally predictable (100% rewardrobability) and gradually strengthens as the indicated reward probabilityecreases. Furthermore, comparing the distribution of the onset latencies ofS and reward responses between striatal and dopamine neurons, we foundo significant differences between them. Together with the fact that stria-um and dopamine neurons have strong direct and indirect fiber connections,hese results suggest that the striatum plays an important role in coding RPEignal by cooperating with dopamine neurons.

oi:10.1016/j.neures.2010.07.1282

2-k26 Neural correlates of category-based prediction ofutcome in the prefrontal cortexunekazu Yamada , Toshio Iijima, Ken-Ichiro Tsutsui

Division of Systems Neuroscience, Tohoku University Graduate School of Lifeciences

e recorded single-unit activity in the monkey prefrontal cortex while theyerformed a task requiring categorization of abstract figures by reward con-ingencies. A stimulus set consisted of 8 stimuli. In a session of several tensf trials, 4 stimuli out of 8 predicted juice delivery, and the other predictedaline delivery. In every new session, the stimulus-outcome combinationsf all stimuli were reversed (stimulus-outcome rule reversal). With thisask design, 4 stimuli within a subset always lead to a common outcome,lthough which specific outcome they led to varied by rule. A series of behav-oral probe test indicated that all monkeys recognized 4 stimuli that alwaysead to a common outcome as a category, and used that information toerform efficiently in the task, especially at the rule reversals. Many neu-ons were found to respond phasically at the stimulus presentation, andere classified into three types depending on their response properties.

he first type (contingency coding neurons) responded commonly to thetimuli which predicted the same outcome. They reversed their stimuluselectivity at every rule reversal. The second type (category coding neu-ons) always responded commonly to 4 stimuli within a category. Theyid not change their stimulus selectivity at the rule reversals. The thirdype (category-specific contingency coding neurons) responded to 4 stimuliithin a category only when they were associated with a specific outcome. In

ddition, another group of neurons showed rule-specific anticipation for thetimulus onset, which may be possibly related to short-term memory of rel-vant rule information. Based on these results, we propose a possible neuronircuit model that integrates category information with currently relevantule information to yield category-specific contingency information and theneneral contingency information, which works for the prediction of futureutcomes.

oi:10.1016/j.neures.2010.07.1283

2-k27 Effects of alcohol (ethanol) on hippocampal CA1euronal activity and hippocampal cerebral blood flow inonscious ratsahori Takenaka 1 , Momoka Tanji 1, Chiaki Megumi 2, Takuyaamano 2, Nobuaki Tsuge 2, Kenju Miki 1

Department of Integrative Physiology, Nara Women’s UniversitySomatech Center, House Foods Co., Chiba

here is mounting evidence that ethanol effects on learning and memoryy altering neuronal activity and regional cerebral blood flow (CBF) in theippocampus. However, little is known regarding effects of ethanol on hip-ocampal neuronal activity and regional CBF in freely behaving rats. In theresent study, hippocampal CA1 neuronal activity and hippocampal CBFere measured simultaneously, and determined quantitative relationship

etween plasma alcohol concentration and hippocampal CA1 neuronal activ-ty and hippocampal CBF. Wistar male rats were instrumented chronically

ith a combined probe made with multiple electrodes (100 �m stainless

teal wires) for measurement of hippocampal CA1 neuronal activity andlass fiber (250 �m o.d.) for measurement of hippocampal CBF and withenous catheter for ethanol infusion. At least 3 days after the surgery, 20% ofthanol (2 g/kg body weight) was infused intravenously over 5 min. Immedi-tely after start of ethanol infusion, the hippocampal CA1 neuronal activity

h 68S (2010) e223–e334 e289

decreased by 50% and then it recovered gradually to the control level. Bycontrast, hippocampal CBF decreased gradually by 10% after the start ofethanol administration. There was a significant (r = 0.89, P < 0.05) inverse lin-ear relationship between plasma ethanol concentration and hippocampalCA1 neuronal activity. There was also a weak (0.05

doi:10.1016/j.neures.2010.07.1284

P2-k28 Amelioration of reversal learning caused by the lossof cholinergic interneuron in the dorsomedial striatumKana Okada 1,2 , Nobuyuki Kai 1, Akira Shiota 3, Masatsugu Ueda 3,Yuji Tsutsui 4, Kazuto Kobayashi 1,2

1 Department Mol. Genet., Fukushima Medical University, Fukushima, Japan2 CREST, JST, Tokyo, Japan 3 PhenixBio, Co., Ltd., Hiroshima, Japan 4 Faculty ofSymbiotic Systems Sci., Fukushima University, Fukushima, Japan

The striatum is a large component in the prefrontal cortex–basal gangliacircuit that plays a critical role in cognitive flexibility including a shift inresponse patterns or strategies. Lesion and pharmacological studies showedthat dorsal striatum involves in a shift in response patterns such as spa-tial reversal learning. Cholinergic interneurons in dorsal striatum, regardedas tonically active neurons, are situated from their anatomical and elec-trophysiological features to influence striatal outputs which may facilitatea shift in response patterns. This study examined the behavioral involve-ment in the spatial reversal learning of the cholinergic interneurons in thedifferent dorsal striatum regions, using the immunotoxin-mediated cell tar-geting. In Experiment 1, the elimination of cholinergic interneuron in dorsalstriatum caused the amelioration the spatial reversal learning in T-mazespatial learning task, regardless of the pre-surgery experience of the samespatial reversal learning in the different room. That elimination did notaffect the spatial learning. In Experiment 2, the elimination of choliner-gic interneurons in dorsomedial striatum ameliorated the reversal learning,but that in dorsolateral striatum did not. In Experiment 3, the elimina-tion of cholinergic interneuron in dorsal striatum caused the facilitationof extinction in T-maze spatial learning task. The results exhibited thatcholinergic interneuron in the dorsomedial striatum are selectively involvedin the spatial reversal learning. Amelioration of spatial reversal learningcaused by cholinergic interneuron deficit might be led from the facilita-tion of extinction in spatial original learning in former sessions in the samemaze.

doi:10.1016/j.neures.2010.07.1285

P2-l01 The role of dopamine D2 receptor-expressing neu-rons in the nucleus accumbens core in operant matchingNobuyuki Kai 1 , Ryoji Fukabori 1, Yuji Tsutsui 2, MotokazuUchigashima 3, Masahiko Watanebe 3, Akira Shiota 4, MasatsuguUeda 4, Kazuto Kobayashi 1

1 Department Molecular genetics, Fukushima Medical University,Fukushima, Japan 2 Faculty of Symbiotic Systems Science, FukushimaUniversity, Fukushima, Japan 3 Department of Anatomy and Embryol-ogy, Hokkaido University Graduate School of Medicine, Sapporo, Japan4 PhoenixBio Co., Ltd, Utsunomiya, Japan

The nucleus accumbens (Nac) core is known for its role in mediating moti-vated behaviors such as lever pressing which are elicited by natural rewardsor incentive stimuli. However, there is little information concerning the neu-ral mechanisms by which appetitive responses are learned. Recent modelssuggest that tonic levels of dopamine in the Nac convey signals correspond-ing to the net rate of rewards, in determining the optimal rate of responding.To investigate a role of Nac core neurons containing dopamine D2 recep-tor (D2R) on the regulation of motivated behavior, we tested a paradigmknown as the matching law that account for response rate as a functionof reinforcement rate. D2R-expressing neurons were selectively removedfrom Nac core of the transgenic rats using immunotoxin-mediated cell tar-geting method. After the treatment, rats were trained to press a lever toget rewards in a series of sessions consisted of six variable interval (VI)schedules ranging from VI 7 s to VI 297 s. VI schedules within each sessionwere presented randomly without replacement. Subjects were exposed tothe VI schedules for 18 sessions. There was no stimulus that signals cur-

rent reward rate and rats were expected to press a lever in proportion tothe expected current reward rate. Immunotoxin-injected transgenic ratsshowed significantly larger divergence from the operant matching behav-ior than the control group in the middle phase (from 7 to 12) of sessions.In addition, the transgenic rats obtained significantly smaller amount ofreward than the control. These results suggest that selective removal of