Kupfermann I, Cohen J L, Mandelbaum D E, Schonberg M, Susswein A J, Weiss K R
Fed Proc. 1979 Jun;38(7):2095-102.
The serotonergic metacerebral cell (MCC) of the mollusk Aplysia produces slow synaptic potentials in motor neurons of the buccal muscle, and increases the rate of ongoing rhythmic burst output of the buccal ganglion. In addition, the MCC acts peripherally to enhance the strength of buccal muscle contractions that are produced by firing of motor neurons. The potentiation of contraction is not associated with any detectable changes of resting membrane potential of muscle cells. Although MCC activity produces a small enhancement of excitatory junctional potentials, several experiments clearly indicate that the MCC has a direct potentiating effect on excitation-contraction coupling. The data suggest that potentiation of contraction might be mediated by cAMP. For example, activity of the MCC enchances the rate of accumulation of cAMP in buccal muscle, application of phosphodiesterase resistant analogs of cAMP potentiates muscle contraction, and a phosphodiesterase inhibitor enhances the effect of MCC stimulation. Recordings from free-moving animals indicate that the MCC becomes activated by exposure of the animal to food stimuli, and that the activation parallels the presence of a food-arousal state. Food-arousal is characterized by enhanced strength and increased frequency of biting responses. Both these effects can result from activity of the MCC. Thus, in this system, modulatory synaptic actions function to provide the substrate for a type behavioral modulation.
软体动物海兔的5-羟色胺能大脑后叶细胞（MCC）在颊肌运动神经元中产生缓慢的突触电位，并增加颊神经节持续节律性爆发输出的频率。此外，MCC在外周起作用，增强运动神经元放电所产生的颊肌收缩强度。收缩增强与肌肉细胞静息膜电位的任何可检测变化均无关。尽管MCC活动会使兴奋性接头电位略有增强，但多项实验清楚地表明，MCC对兴奋-收缩偶联具有直接的增强作用。数据表明，收缩增强可能由环磷酸腺苷（cAMP）介导。例如，MCC的活动会提高颊肌中cAMP的积累速率，应用cAMP的磷酸二酯酶抗性类似物可增强肌肉收缩，而磷酸二酯酶抑制剂可增强MCC刺激的效果。对自由活动动物的记录表明，动物接触食物刺激会激活MCC，且这种激活与食物激发状态的存在平行。食物激发的特征是咬食反应的强度增强和频率增加。这两种效应都可能是由MCC的活动引起的。因此，在这个系统中，调制性突触作用为一种行为调制类型提供了基础。
