Identified serotonergic neurons in the Tritonia swim CPG activate both ionotropic and metabotropic receptors
Identified serotonergic neurons in the Tritonia swim CPG activate both ionotropic and metabotropic receptors
复制标题
DOI：
10.1152/jn.2001.85.1.476
复制
发表时间：
2001-01-01
影响因子：
2.5
通讯作者：
Katz, PS
中科院分区：
文献类型：
--
作者：
Clemens, S;Katz, PS
虽然已知G蛋白偶联（代谢型）受体调节运动模式的产生，但裸鳃类软体动物Tritonia diomedea的逃逸游泳中枢模式发生器（CPG）的证据表明，它们也可能参与运动模式本身的产生。背侧游泳中间神经元（DSI）是Tritonia游泳CPG固有的神经元，可诱发其他CPG神经元和前运动中间神经元的双成分突触电位。快速和缓慢的成分先前被证明是由于5-羟色胺（5-HT）作用于不同的突触后受体。我们发现，阻断或促进代谢型受体在突触后前运动中间神经元的差异影响快，慢突触反应DSI刺激。通过离子电渗注射GDP-类似物鸟苷5 '-O-（2-硫代二磷酸）（GDP-β-S）阻断G蛋白激活对DTI诱发的快兴奋性突触后电位（EPSP）没有显著影响，但使慢成分的振幅降低50%以上。注射GTP类似物鸟苷5 '-O-（3-硫代三磷酸）（GTP-γ-S）和5'-鸟苷酰-亚氨二磷酸（5 '-guanyl-imidodiophosphate），以延长G蛋白激活，对快速成分有混合效应，但增加了DSI诱发反应的缓慢成分的幅度和持续时间，并且在重复DSI刺激下，导致持续去极化。这些结果表明，快速组件的双相突触电位诱发的多巴胺能CPG神经元上的前运动中间神经元的离子型受体（5-HT门控离子通道）介导的，而缓慢的组件介导的G-蛋白偶联受体。代谢型受体的类似突触激活也可能在CPG本身内发现，在那里它可以对运动模式的产生直接影响。
Although G-protein-coupled (metabotropic) receptors are known to modulate the production of motor patterns, evidence from the escape swim central pattern generator (CPG) of the nudibranch mollusk, Tritonia diomedea, suggests that they might also participate in the generation of the motor pattern itself. The dorsal swim interneurons (DSIs), identified serotonergic neurons intrinsic to the Tritonia swim CPG, evoke dual component synaptic potentials onto other CPG neurons and premotor interneurons. Both the fast and slow components were previously shown to be due to serotonin (5-HT) acting at distinct postsynaptic receptors. We find that blocking or facilitating metabotropic receptors in a postsynaptic premotor interneuron differentially affects the fast and slow synaptic responses to DSI stimulation. Blocking G-protein activation by iontophoretically injecting the GDP-analogue guanosine 5'-O-( 2-thiodiphosphate) (GDP-beta -S) did not significantly affect the DSI-evoked fast excitatory postsynaptic potential (EPSP) but decreased the amplitude of the slow component more than 50%. Injection of the GTP analogues guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma -S) and 5'-guanylyl-imidodiphosphate, to prolong G-protein activation, had mixed effects on the fast component but increased the amplitude and duration of the slow component of the DSI-evoked response and, with repeated DSI stimulation, led to a persistent depolarization. These results indicate that the fast component of the biphasic synaptic potential evoked by a serotonergic CPG neuron onto premotor interneurons is mediated by ionotropic receptors (5-HT-gated ion channels), whereas the slow component is mediated by G-protein-coupled receptors. A similar synaptic activation of metabotropic receptors might also be found within the CPG itself, where it could exert a direct influence onto motor pattern generation.