Liebeswar G, Goldman J E, Koester J, Mayeri E
J Neurophysiol. 1975 Jul;38(4):767-79. doi: 10.1152/jn.1975.38.4.767.
In the abdominal ganglion of Aplysia californica, seven motoneurons have been described which modulate the myogenic heart beat and vasomotor tone (28). These neurons mediate their motor effects by chemical transmission. In this paper we have attempted to specify the transmitters of six of these motoneurons. We have 1) studied the effects of several common transmitters on the innervated structures and compared these effects with the effects of firing the motoneurons, 2) examined whether blocking agents influence similarly the effect of a putative transmitter applied to the innervated structure and the effect of firing a motoneuron, and 3) tested the capability of the motoneurons to synthesize the putative transmitters from precursors. The positive inotropic and chronotropic effects of firing the excitor motoneuron RB(HE) were mimicked by perfusion of the heart with serotonin at a low concentration. Cinanserin blocked both the effects of motoneuron excitation and serotonin perfusion. RB(HE) was also shown to synthesize [3H]serotonin from L-[3H]tryptophan injected directly into the cell body. The effects of firing the two LD(HI) heart-inhibitory motoneurons were mimicked by perfusion of the heart with acetylcholine. Benzoquinonium blocked the effects of the inhibitory motoneuron and acetylcholine perfusion. Perfusion with arecoline also inhibited the heart beat. Acetylcholine applied to the arteries mimicked the vasoconstriction caused by the LB(VC) motoneurons. Aortic constriction in response to activity in LB(VC) cells or to acetylcholine was blocked by hexamethonium and curare. The heart inhibitor and vasoconstrictor motoneurons synthesized [3H] acetylcholine from [3H] choline injected into their cell bodies. Thus, as in vertebrates, acetylcholine mediates inhibition to the heart. Unlike vertebrates, however, serotonin mediates excitation to the heart and acetylcholine mediates peripheral vasoconstriction.
在加州海兔的腹神经节中，已描述了七个运动神经元，它们可调节肌源性心跳和血管运动张力（28）。这些神经元通过化学传递介导其运动效应。在本文中，我们试图确定其中六个运动神经元的递质。我们进行了以下研究：1）研究了几种常见递质对受支配结构的影响，并将这些影响与激发运动神经元的影响进行比较；2）检查阻断剂是否同样影响应用于受支配结构的假定递质的作用以及激发运动神经元的作用；3）测试运动神经元从前体合成假定递质的能力。低浓度血清素灌注心脏可模拟激发兴奋性运动神经元RB(HE)所产生的正性变力和变时效应。辛那色林可阻断运动神经元兴奋和血清素灌注的效应。还发现RB(HE)可从直接注入细胞体的L-[3H]色氨酸合成[3H]血清素。灌注乙酰胆碱可模拟激发两个LD(HI)心脏抑制性运动神经元的效应。苯甲喹铵可阻断抑制性运动神经元和乙酰胆碱灌注的效应。灌注槟榔碱也可抑制心跳。应用于动脉的乙酰胆碱可模拟由LB(VC)运动神经元引起的血管收缩。六甲铵和箭毒可阻断LB(VC)细胞活动或乙酰胆碱引起的主动脉收缩。心脏抑制性和血管收缩性运动神经元可从注入其细胞体的[3H]胆碱合成[3H]乙酰胆碱。因此，与脊椎动物一样，乙酰胆碱介导对心脏的抑制作用。然而，与脊椎动物不同的是，血清素介导对心脏的兴奋作用，而乙酰胆碱介导外周血管收缩。
