Cellular bases of noncoincidence learning in Hermissenda

描述(由申请人提供)：我们将研究软体动物Hermissenda(H.C.)中潜在的非符合学习和条件抑制的细胞过程。通过将动物暴露在经典的条件反射过程中，光(CS)发出不旋转的信号(US)，这一基本但鲜为人知的联想学习类别可以很容易地在H.C.中产生。光和旋转的显式不配对(EU)呈现增加了动物的趋光行为。我们将继续研究CS通路中B型和A型光感受器产生的持续性兴奋性变化。我们发现，接受EU训练而不是对照条件的动物的眼部B型细胞，其稳态去极化发生器电位(SSGP)持续下降，光诱发的尖峰频率下降。我们将完成我们的研究，证明A型细胞与EU训练表现出互补的变化：SSGP增加和光诱导的尖峰频率。光感受器兴奋性改变的离子基础将用电压钳、离子替代和药理学方法来研究。我们将完成我们的研究，表明B细胞兴奋性的降低是由于体细胞K+电流(IA和IK-Ca)的持续增加，并进一步描述了相关的机制。将研究钙依赖过程对B细胞光反应变化表达的贡献，以及IA变化对EU的贡献降低尖峰频率。我们还将确定导致A型细胞兴奋性增加的离子电导变化。我们将通过在学习后保留几天的突触前和突触后细胞内同步记录，来测试欧盟在B-B和B-A光感受器之间的突触传递方面发生的变化。我们将继续我们的研究，通过使用体外条件化方案诱导B细胞兴奋性降低，并将测试钙、蛋白磷酸酶1(PP1)和花生四烯酸(AA)是否参与了与EU相关的B细胞兴奋性降低的产生。由于时态变化的[钙]i水平可能是B细胞兴奋性因光和旋转的不同刺激方案而降低或增加的关键因素，因此我们将在光后的不同时间点测量B细胞的[Ca2+]i水平。比率计量型Fura-2成像方法将被用来观察导致EU条件作用成功的刺激间间隔是否与特定的[钙]i水平相匹配。

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.