Antonsen Brian L, Edwards Donald H
Biology Department, Georgia State University, Atlanta, GA, USA.
J Neurophysiol. 2007 Dec;98(6):3494-504. doi: 10.1152/jn.00331.2007. Epub 2007 Sep 26.
The lateral giant (LG) command neuron of crayfish responds to an attack directed at the abdomen by triggering a single highly stereotyped escape tail flip. Experimentally applied serotonin (5-hydroxytrptamine, 5-HT) can increase or decrease LG's excitability, depending on the concentration, rate, and duration of 5-HT application. Here we describe three physiological mechanisms that mediate serotonergic facilitation of LG. Two processes strengthen electrical coupling between the primary mechanosensory afferent neurons and LG: first, an early increase in the conductance of electrical synapses between primary afferent neurons and LG dendrites and second, an early increase in the membrane resistance of LG dendrites. The increased coupling facilitates LG's synaptic response and it promotes recruitment of weakly excited afferent neurons to contribute to the response. Third, a delayed increase in the membrane resistance of proximal regions of LG increases the cell's input resistance near the initial segment. Together these mechanisms contribute to serotonergic facilitation of LG's response.
小龙虾的外侧巨（LG）指令神经元通过触发单次高度刻板的逃逸尾扇反应，对指向腹部的攻击做出响应。实验应用的血清素（5-羟色胺，5-HT）可根据5-HT应用的浓度、速率和持续时间，增加或降低LG的兴奋性。在此，我们描述了介导LG血清素能易化作用的三种生理机制。两个过程增强了初级机械感觉传入神经元与LG之间的电耦合：第一，初级传入神经元与LG树突之间电突触的电导早期增加；第二，LG树突的膜电阻早期增加。增加的耦合促进了LG的突触反应，并促进募集弱兴奋的传入神经元以促成该反应。第三，LG近端区域膜电阻的延迟增加，增加了细胞在起始段附近的输入电阻。这些机制共同促成了LG反应的血清素能易化作用。
