Department of Biology, Case Western Reserve University, Degrace Hall 106, Cleveland, Ohio 44106, USA.
J Neurophysiol. 2010 Aug;104(2):654-64. doi: 10.1152/jn.00846.2009. Epub 2010 Jun 2.
Neuromodulation is well known to provide plasticity in pattern generating circuits, but few details are available concerning modulation of motor pattern coordination. We are using the crustacean stomatogastric nervous system to examine how co-expressed rhythms are modulated to regulate frequency and maintain coordination. The system produces two related motor patterns, the gastric mill rhythm that regulates protraction and retraction of the teeth and the pyloric rhythm that filters food. These rhythms have different frequencies and are controlled by distinct mechanisms, but each circuit influences the rhythm frequency of the other via identified synaptic pathways. A projection neuron, MCN1, activates distinct versions of the rhythms, and we show that hormonal dopamine concentrations modulate the MCN1 elicited rhythm frequencies. Gastric mill circuit interactions with the pyloric circuit lead to changes in pyloric rhythm frequency that depend on gastric mill rhythm phase. Dopamine increases pyloric frequency during the gastric mill rhythm retraction phase. Higher gastric mill rhythm frequencies are associated with higher pyloric rhythm frequencies during retraction. However, dopamine slows the gastric mill rhythm frequency despite the increase in pyloric frequency. Dopamine reduces pyloric circuit influences on the gastric mill rhythm and upregulates activity in a gastric mill neuron, DG. Strengthened DG activity slows the gastric mill rhythm frequency and effectively reduces pyloric circuit influences, thus changing the frequency relationship between the rhythms. Overall dopamine shifts dependence of frequency regulation from intercircuit interactions to increased reliance on intracircuit mechanisms.
神经调节被广泛认为可以提供模式生成电路的可塑性，但关于运动模式协调的调节的细节知之甚少。我们正在使用甲壳类动物的口胃神经系统来研究如何调节共表达的节律以调节频率并维持协调。该系统产生两种相关的运动模式，即调节牙齿伸展和缩回的胃磨节律和过滤食物的幽门节律。这些节律具有不同的频率，由不同的机制控制，但每个电路都通过已识别的突触途径影响另一个电路的节律频率。一个投射神经元 MCN1 激活不同版本的节律，我们表明激素多巴胺浓度调节 MCN1 引发的节律频率。胃磨电路与幽门电路的相互作用导致幽门节律频率的变化取决于胃磨节律相位。在胃磨节律收缩阶段，多巴胺增加幽门频率。在收缩期间，较高的胃磨节律频率与较高的幽门节律频率相关。然而，尽管幽门频率增加，多巴胺仍会降低胃磨节律频率。多巴胺降低了幽门电路对胃磨节律的影响，并上调了 DG 胃磨神经元的活动。DG 活动的增强会降低胃磨节律的频率，并有效地降低幽门电路的影响，从而改变节律之间的频率关系。总体而言，多巴胺将频率调节的依赖性从电路间相互作用转移到对内部电路机制的依赖增加。
