Johnson B R, Harris-Warrick R M
Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853.
J Neurosci. 1990 Jul;10(7):2066-76. doi: 10.1523/JNEUROSCI.10-07-02066.1990.
Graded chemical synaptic transmission is important for establishing the motor patterns produced by the pyloric central pattern generator (CPG) circuit of the lobster stomatogastric ganglion (Raper, 1979; Anderson and Barker, 1981; Graubard et al., 1983). We examined the modulatory effects of the amines dopamine (DA), serotonin (5-HT), and octopamine (Oct) on graded synaptic transmission at all the central chemical synapses made by the pyloric dilator (PD) neuron onto its follower cells, using synaptic input-output curves measured from cell somata. DA strongly reduced the graded synaptic strength at all the PD synapses. DA reduction of chemical synaptic strength from PD onto the inferior cardiac (IC) neuron could change the sign of synaptic interaction between these 2 cells from inhibitory to excitatory by uncovering a weak electrical connection. 5-HT had weaker and more variable effects, reducing graded synaptic strength from the PD onto the lateral pyloric and pyloric neurons and enhancing the weak synapse from the PD to the IC cell. Oct strongly enhanced the graded synaptic strength at all the PD central synapses. Oct enhancement of graded synaptic strength between the PD and IC cells could also change the sign of the interaction: weak, excitatory electrical coupling, which was sometimes dominant before Oct, was masked by the enhanced chemical inhibitory interaction during Oct application. Measurements of electrical coupling between 2 PD cells and between 2 postsynaptic cells suggest that Oct does not change the input resistance of these cells and may act directly at the PD synapses. The effects of DA and 5-HT are most easily explained by their general reductions in pre- and postsynaptic input resistance. DA, 5-HT, and Oct each produce a distinct pyloric motor pattern (Flamm and Harris-Warrick, 1986a). These amine-induced motor patterns may be explained by the unique actions of each amine on the intrinsic membrane properties of different pyloric CPG neurons (Flamm and Harris-Warrick, 1986b) and by modulation of graded synaptic transmission between the pyloric neurons.
分级化学突触传递对于建立龙虾口胃神经节幽门中央模式发生器（CPG）回路产生的运动模式很重要（拉珀，1979年；安德森和巴克，1981年；格劳巴德等人，1983年）。我们使用从细胞体测量的突触输入-输出曲线，研究了多巴胺（DA）、5-羟色胺（5-HT）和章鱼胺（Oct）对幽门扩张肌（PD）神经元与其跟随细胞之间所有中央化学突触处分级突触传递的调节作用。多巴胺强烈降低了所有PD突触处的分级突触强度。多巴胺降低从PD到下心（IC）神经元的化学突触强度，可能通过揭示微弱的电连接，改变这两个细胞之间突触相互作用的符号，从抑制变为兴奋。5-羟色胺的作用较弱且更具变异性，降低了从PD到外侧幽门和幽门神经元的分级突触强度，并增强了从PD到IC细胞的微弱突触。章鱼胺强烈增强了所有PD中央突触处的分级突触强度。章鱼胺增强PD和IC细胞之间的分级突触强度，也可能改变相互作用的符号：在章鱼胺作用前有时占主导的微弱兴奋性电耦合，在应用章鱼胺期间被增强的化学抑制性相互作用所掩盖。对两个PD细胞之间以及两个突触后细胞之间电耦合的测量表明，章鱼胺不会改变这些细胞的输入电阻，可能直接作用于PD突触。多巴胺和5-羟色胺的作用最容易通过它们对突触前和突触后输入电阻的普遍降低来解释。多巴胺、5-羟色胺和章鱼胺各自产生独特的幽门运动模式（弗拉姆和哈里斯-沃里克，1986a）。这些胺诱导的运动模式，可能由每种胺对不同幽门CPG神经元内在膜特性的独特作用（弗拉姆和哈里斯-沃里克，1986b）以及幽门神经元之间分级突触传递的调节来解释。
