Whitaker Leslie R, Warren Brandon L, Venniro Marco, Harte Tyler C, McPherson Kylie B, Beidel Jennifer, Bossert Jennifer M, Shaham Yavin, Bonci Antonello, Hope Bruce T
Behavioral Neuroscience Research Branch and
Behavioral Neuroscience Research Branch and.
J Neurosci. 2017 Sep 6;37(36):8845-8856. doi: 10.1523/JNEUROSCI.3761-16.2017. Epub 2017 Aug 4.
Learned associations between environmental stimuli and rewards drive goal-directed learning and motivated behavior. These memories are thought to be encoded by alterations within specific patterns of sparsely distributed neurons called neuronal ensembles that are activated selectively by reward-predictive stimuli. Here, we use the Fos promoter to identify strongly activated neuronal ensembles in rat prelimbic cortex (PLC) and assess altered intrinsic excitability after 10 d of operant food self-administration training (1 h/d). First, we used the Daun02 inactivation procedure in male FosLacZ-transgenic rats to ablate selectively Fos-expressing PLC neurons that were active during operant food self-administration. Selective ablation of these neurons decreased food seeking. We then used male FosGFP-transgenic rats to assess selective alterations of intrinsic excitability in Fos-expressing neuronal ensembles (FosGFP) that were activated during food self-administration and compared these with alterations in less activated non-ensemble neurons (FosGFP). Using whole-cell recordings of layer V pyramidal neurons in an brain slice preparation, we found that operant self-administration increased excitability of FosGFP neurons and decreased excitability of FosGFP neurons. Increased excitability of FosGFP neurons was driven by increased steady-state input resistance. Decreased excitability of FosGFP neurons was driven by increased contribution of small-conductance calcium-activated potassium (SK) channels. Injections of the specific SK channel antagonist apamin into PLC increased Fos expression but had no effect on food seeking. Overall, operant learning increased intrinsic excitability of PLC Fos-expressing neuronal ensembles that play a role in food seeking but decreased intrinsic excitability of Fos non-ensembles. Prefrontal cortex activity plays a critical role in operant learning, but the underlying cellular mechanisms are unknown. Using the chemogenetic Daun02 inactivation procedure, we found that a small number of strongly activated Fos-expressing neuronal ensembles in rat PLC play an important role in learned operant food seeking. Using GFP expression to identify Fos-expressing layer V pyramidal neurons in prelimbic cortex (PLC) of FosGFP-transgenic rats, we found that operant food self-administration led to increased intrinsic excitability in the behaviorally relevant Fos-expressing neuronal ensembles, but decreased intrinsic excitability in Fos neurons using distinct cellular mechanisms.
环境刺激与奖励之间的习得性关联驱动着目标导向学习和动机行为。这些记忆被认为是由稀疏分布的神经元的特定模式（称为神经元集群）内的变化所编码，这些神经元集群被奖励预测性刺激选择性激活。在这里，我们使用Fos启动子来识别大鼠前边缘皮层（PLC）中强烈激活的神经元集群，并评估在进行10天的操作性食物自我给药训练（每天1小时）后内在兴奋性的变化。首先，我们在雄性FosLacZ转基因大鼠中使用道诺霉素02失活程序，选择性地消融在操作性食物自我给药期间活跃的表达Fos的PLC神经元。选择性消融这些神经元会减少食物寻求行为。然后，我们使用雄性FosGFP转基因大鼠来评估在食物自我给药期间被激活的表达Fos的神经元集群（FosGFP）中内在兴奋性的选择性变化，并将其与激活程度较低的非集群神经元（FosGFP）的变化进行比较。通过在脑片制备中对V层锥体神经元进行全细胞记录，我们发现操作性自我给药增加了FosGFP神经元的兴奋性，降低了FosGFP神经元的兴奋性。FosGFP神经元兴奋性的增加是由稳态输入电阻的增加驱动的。FosGFP神经元兴奋性的降低是由小电导钙激活钾（SK）通道贡献的增加驱动的。向PLC注射特定的SK通道拮抗剂蜂毒明肽会增加Fos表达，但对食物寻求行为没有影响。总体而言，操作性学习增加了在食物寻求中起作用的PLC表达Fos的神经元集群的内在兴奋性，但降低了Fos非集群神经元的内在兴奋性。前额叶皮层活动在操作性学习中起关键作用，但其潜在的细胞机制尚不清楚。使用化学遗传学道诺霉素02失活程序，我们发现大鼠PLC中少数强烈激活的表达Fos的神经元集群在习得性操作性食物寻求中起重要作用。通过使用GFP表达来识别FosGFP转基因大鼠前边缘皮层（PLC）中表达Fos的V层锥体神经元，我们发现操作性食物自我给药导致行为相关的表达Fos的神经元集群的内在兴奋性增加，但使用不同的细胞机制降低了Fos神经元的内在兴奋性。
