Cellular bases of noncoincidence learning in Hermissenda

描述（由申请人提供）：我们将研究在软体动物Hermissenda（H.C.）的非巧合学习和条件抑制的细胞过程。这种基本的，但理解甚少的联想学习类别可以很容易地在H. c.，通过将动物暴露于经典的条件反射程序，其中光（CS）发出旋转不存在的信号（US）。光和旋转的显式不成对（EU）呈现增加了动物的趋光行为。我们将继续表征CS通路内B型和A型光感受器中产生的持续兴奋性变化。我们已经发现，眼B型细胞从欧盟训练，但不是控制条件下，动物表现出持续下降，其稳态去极化发生器电位（SSGP），并减少光诱发的尖峰频率。我们将完成我们的研究，证明A型细胞显示出与EU训练互补的变化：SSGP和光引发的尖峰频率增加。光感受器兴奋性变化的离子基础将使用电压钳、离子取代和药理学方法进行研究。我们将完成我们的研究，表明B细胞的兴奋性降低是由于持续增加的体细胞K+电流（IA和IK-Ca），并进一步表征负责的机制。将研究钙依赖性过程对B细胞光响应变化表达的贡献，以及IA变化对EU峰频率降低的贡献。我们还将确定负责A型细胞兴奋性增加的离子电导变化。我们将测试的发生欧盟产生的变化，在B-B和B-A光感受器之间的突触传递，通过同时从前和突触后细胞的保留日学习后的细胞内记录。我们将继续研究通过使用体外预处理方案诱导B细胞兴奋性降低，并将检测钙、蛋白磷酸酶1（PP 1）和花生四烯酸（AA）参与产生EU相关的B细胞兴奋性降低。由于时间变化的[Ca 2 +]i水平可能是决定B细胞是否由于涉及光和旋转的不同刺激方案而表现出兴奋性降低或增加的关键因素，因此我们将在光照射后的不同时间点测量B细胞[Ca 2 +]i水平。将使用比率fura-2成像方法观察导致成功EU调节的刺激间隔是否与特定[Ca 2 +]i水平匹配。

DESCRIPTION (provided by applicant): We will study cellular processes underlying non-coincidence learning and conditioned inhibition in the mollusk Hermissenda (H.c.). This fundamental, but poorly understood category of associative learning can be readily produced in H.c., by exposing animals to a classical conditioning procedure where light (the CS) signals the absence of rotation (the US). Explicitly unpaired (EU) presentations of light and rotation increase animals' phototactic behavior. We will continue to characterize the persistent excitability changes that are produced in Type B and A photoreceptors within the CS-pathway. We have found that ocular Type B cells from EU-trained, but not control-condition, animals exhibit persistent decreases in their steady-state depolarizing generator potentials (SSGPs), and decreases in light-evoked spike frequencies. We will complete our studies demonstrating that Type A cells show complementary changes with EU-training: increases in SSGPs and light-elicited spike frequency. The ionic bases of the changes in photoreceptor excitability will be studied using voltage-clamp, ion substitution, and pharmacological methods. We will complete our studies that indicate that the decreased excitability of B cells is due to persistent increases in somatic K+ currents (IA and IK-Ca), and further characterize the mechanisms responsible. The contribution of calcium-dependent processes to expression of B cell photoresponse changes will be studied, as well as the contribution of changes in IA to the EU decreases in spike frequency. We will also determine the ionic conductance changes responsible for the increased excitability of Type A cells. We will test for the occurrence of EU-produced changes in synaptic transmission between B-B and B-A photoreceptors, through simultaneous intracellular recordings from pre- and postsynaptic cells on retention days following learning. We will continue our studies of the induction of decreases in B cell excitability, through the use of an in vitro conditioning protocol, and will test for the involvement of calcium, protein phosphatase 1 (PP1), and arachidonic acid (AA) in the production of the EU-associated decreases in B cell excitability. Because temporally-varying [Ca2+]i levels may be a crucial factor as to whether B cells exhibit excitability decreases or increases due to different stimulation regimens involving light and rotation, we will measure B cell [Ca2+]i levels at different time points following light. Ratiometric fura-2 imaging methods will be used to see if the interstimulus intervals that result in successful EU-conditioning match a specific [Ca2+]i level.