Talk A C, Muzzio I A, Matzel L D
Department of Psychology, Rutgers University, New Brunswick, NJ 08903, USA.
Brain Res. 1997 Mar 21;751(2):196-205. doi: 10.1016/s0006-8993(96)01397-2.
During contiguous pairings of light and rotation, B photoreceptors in the Hermissenda eye undergo an increase in excitability that contributes to a modification of several light-elicited behaviors. This excitability increase requires a light-induced rise in intracellular Ca2+ in the photoreceptor concomitant with transmitter binding to G protein-coupled receptors as a result of presynaptic vestibular hair cell stimulation. Phospholipases and arachidonic acid (ArA) are here reported to be involved in independent signal transduction pathways that underlie both receptor function and activity-dependent facilitation of the B photoreceptor. 4-Bromophenacyl bromide (BPB), an inhibitor of phospholipases A2 (PLA2) and C (PLC), blocked the generation of light-induced depolarizing generator potentials, but had no affect on the inhibitory postsynaptic potential (IPSP) in the B cell that results from hair cell stimulation. Quinacrine, which predominantly blocks the activity of PLA2 in neurons, had no affect on either the light response or the IPSP, but did block increases in excitability (i.e. increased input resistance and elicited spike rate) of the B cell that results from pairings of light and presynaptic vestibular stimulation (i.e., in vitro associative conditioning). Neither nordihydroquararetic acid (NDGA), which inhibits metabolism of ArA by cyclooxygenase, nor indomethacin, which inhibits lipoxygenase metabolism of ArA, affected the light response or IPSP, but both blocked the increases in excitability in the B cell that accompanied in vitro conditioning. In combination with earlier results, these data suggest that ArA activates PKC in a synergistic fashion with Ca2+ and diacylglycerol in the B cell, and suggest that PLA2-induced ArA release, though not necessary for transduction of light or the hair cell-induced IPSP in the B cell, is a critical component of the convergence of signals that precipitates associative facilitation in this system.
在光与旋转的连续配对过程中，滨沙蚕眼中的B光感受器兴奋性增加，这有助于改变几种光诱发行为。这种兴奋性增加需要光诱导光感受器细胞内Ca2+升高，同时由于突触前前庭毛细胞刺激，递质与G蛋白偶联受体结合。据报道，磷脂酶和花生四烯酸（ArA）参与了独立的信号转导途径，这些途径是B光感受器受体功能和活动依赖性易化的基础。4-溴苯甲酰溴（BPB）是磷脂酶A2（PLA2）和C（PLC）的抑制剂，它阻断了光诱导的去极化发生器电位的产生，但对毛细胞刺激引起的B细胞抑制性突触后电位（IPSP）没有影响。喹吖因主要阻断神经元中PLA2的活性，对光反应或IPSP均无影响，但确实阻断了光与突触前前庭刺激配对（即体外联合条件反射）导致的B细胞兴奋性增加（即输入电阻增加和诱发的放电频率增加）。抑制ArA经环氧合酶代谢的去甲二氢愈创木酸（NDGA）和抑制ArA经脂氧合酶代谢的吲哚美辛，均未影响光反应或IPSP，但两者都阻断了体外条件反射时B细胞兴奋性的增加。结合早期结果，这些数据表明，ArA与Ca2+和二酰甘油协同激活B细胞中的蛋白激酶C，并表明PLA2诱导的ArA释放虽然不是B细胞光转导或毛细胞诱导的IPSP所必需的，但却是该系统中促成联合易化的信号汇聚的关键组成部分。
