Büschges A, Kittmann R, Ramirez J M
Faculty of Biology, University of Kaiserslautern, Germany.
J Neurobiol. 1993 May;24(5):598-610. doi: 10.1002/neu.480240506.
The modulatory actions of the biogenic amine octopamine on the femur tibia (FT) control loop in the stick insect Carausius morosus were examined. The response properties of the FT control loop were determined under open loop conditions. Mechanical stimulation of the femoral chordotonal organ (fCO) was the input and tibial movement and motoneuronal activity were measured as the output of the system. Following octopamine injection into the hemolymph of intact, inactive animals, two consecutive phases occurred at the behavioral level. Octopamine caused initially an activation of the animal. During this first phase (3.5-12 min duration) the response properties of the FT control loop were similar to those found in animals that were activated by tactile stimuli under normal conditions. Afterward, animals became inactive. During this second phase (15-20 min duration), the gain of the control loop was zero and no resistance reflex in the FT joint was generated in response to fCO stimulation. However, active movements of the tibia could still be elicited. As we could show in restrained animals, where DL-octopamine was applied topically onto the undesheated mesothoracic ganglion, the complete suppression of the resistance reflex on the motoneuronal level was dose dependent starting at concentrations of 5 x 10(-3) M octopamine. We could show that octopamine specifically suppressed the pathways involved in the resistance reflex, while feedback loop responses to fCO stimuli typical for active animals could still be elicited. Our results indicate that an increase in the octopamine concentration mimicks activation of the animal: Properties being characteristic for the control of the FT joint in the inactive animal are inhibited by octopamine, while properties of the FT control loop typical for the active animal appear to be facilitated following octopamine injection. The results clearly demonstrate that different pathways in the neuronal network underlying the FT control loop are involved in the responses of the control loop to fCO stimuli in the inactive and active behavioral states of the stick insect.
研究了生物胺章鱼胺对竹节虫墨胸斑腿蝗股胫（FT）控制回路的调节作用。在开环条件下测定了FT控制回路的反应特性。以股弦音器官（fCO）的机械刺激作为输入，测量胫节运动和运动神经元活动作为系统的输出。向完整、不活动动物的血淋巴中注射章鱼胺后，行为水平上出现了两个连续阶段。章鱼胺最初会使动物兴奋。在第一阶段（持续3.5 - 12分钟），FT控制回路的反应特性与正常条件下经触觉刺激激活的动物相似。之后，动物变得不活动。在第二阶段（持续15 - 20分钟），控制回路的增益为零，对fCO刺激在FT关节不产生阻力反射。然而，仍可诱发胫节的主动运动。正如我们在受约束动物身上所展示的，将DL - 章鱼胺局部应用于未加热的中胸神经节，从5×10⁻³ M章鱼胺浓度开始，运动神经元水平上阻力反射的完全抑制呈剂量依赖性。我们能够证明章鱼胺特异性地抑制了参与阻力反射的通路，而对活跃动物典型的fCO刺激的反馈回路反应仍可诱发。我们的结果表明，章鱼胺浓度的增加模拟了动物的激活：不活动动物中FT关节控制的特征性特性被章鱼胺抑制，而活跃动物典型的FT控制回路特性在注射章鱼胺后似乎得到促进。结果清楚地表明，FT控制回路基础神经网络中的不同通路参与了竹节虫在不活动和活跃行为状态下控制回路对fCO刺激的反应。
