Jordan R, Cohen K P, Kirk M D
Division of Biological Sciences, University of Missouri, Columbia 65211.
J Exp Zool. 1993 Apr 1;265(5):496-506. doi: 10.1002/jez.1402650505.
To further define the control of intrinsic buccal muscles by identified motoneurons B11, B15, and B16 in Aplysia californica, we made physiological recordings from semi-intact and isolated preparations of the buccal ganglia and buccal mass. B15 and B16 were previously known to innervate muscle 15 (also called the accessory radula closer muscle). We show here that these motoneurons also innervate other buccal muscles ipsilateral to their cell bodies; for example, B15 reliably innervates and can cause contraction in intrinsic muscle I4. Likewise, B11 appears to innervate all of the intrinsic buccal muscles, but elicits contractions only in I4. The form and time course of synaptic plasticity displayed by these motoneurons is common to all the muscles they innervate. No evidence for electrical coupling between fibers of adjacent muscles could be obtained, suggesting that all recorded innervation is direct. Like B15 and B16 (Cohen et al., '78), B11 neuromuscular synapses appear to be cholinergic, since they are reversibly antagonized by hexamethonium and d-tubocurarine (acetylcholine [ACh] receptor antagonists). In addition, direct application of ACh elicits depolarizing responses and contractions in I4 which are also blocked by hexamethonium. Application of glutamate and GABA do not elicit depolarizations or contractions in I4 or I5. We conclude that these motoneurons control radula position through complex synaptic actions on multiple intrinsic buccal muscles, using ACh as their conventional transmitter.
为了进一步明确加州海兔中已鉴定的运动神经元B11、B15和B16对颊内肌的控制，我们对颊神经节和颊块的半完整及分离标本进行了生理学记录。此前已知B15和B16支配肌肉15（也称为副齿舌闭合肌）。我们在此表明，这些运动神经元还支配与其细胞体同侧的其他颊肌；例如，B15可靠地支配固有肌I4并可使其收缩。同样，B11似乎支配所有颊内肌，但仅在I4中引发收缩。这些运动神经元所表现出的突触可塑性的形式和时间进程在它们所支配的所有肌肉中都是相同的。未获得相邻肌肉纤维之间存在电耦合的证据，这表明所有记录到的神经支配都是直接的。与B15和B16（科恩等人，1978年）一样，B11神经肌肉突触似乎是胆碱能的，因为它们可被六甲铵和d - 筒箭毒碱（乙酰胆碱[ACh]受体拮抗剂）可逆性拮抗。此外，直接施加ACh会在I4中引发去极化反应和收缩，这些反应也会被六甲铵阻断。施加谷氨酸和GABA不会在I4或I5中引发去极化或收缩。我们得出结论，这些运动神经元通过对多个颊内肌的复杂突触作用来控制齿舌位置，使用ACh作为其传统递质。
