Wieland S J, Gelperin A
J Neurosci. 1983 Sep;3(9):1735-45. doi: 10.1523/JNEUROSCI.03-09-01735.1983.
A neural system within the cerebral and buccal ganglia of the terrestrial mollusc Limax maximus responds to lip chemostimulation by emitting a feeding motor program (FMP) in vivo and in vitro. We have analyzed chemically the cerebral and buccal ganglia of Limax for neurotransmitters involved in controlling expression of FMP. Dopamine was found in clusters of cells in and the neuropil of the cerebral ganglia at a concentration of 62 pmol/ganglion; a large proportion of such dopamine-containing cells projected to the lips. The buccal ganglia contained several small dopaminergic cells and large amounts of dopamine in the neuropil; the measured concentration was 10 pmol/ganglion. Exogenous dopamine applied to the cerebral and buccal ganglia in vitro between 10(-7) M and 3 X 10(-6) M excited an autoactive salivary duct motor neuron (FB) and inhibited an autoactive secretomotor neuron (BSN). Concentrations of dopamine between 3 X 10(-6) M and 3 X 10(-5) M triggered FMP output, with an increased probability of triggering at higher concentrations of dopamine. ADTN and SK&F38393 were potent agonists in this system, whereas ergonovine was the only potent antagonist found; none of the neuroleptics tested was effective. Thus, the Limax system shows agonist responses similar to the vertebrate D1 receptors, but its antagonist-binding properties appear to have requirements quite different from vertebrate receptors. The effects of exogenous serotonin differed from dopamine's effects; serotonin excited BSN and several buccal motor neurons, could not elicit synchronized motor program cycling, and was not efficiently blocked by ergonovine. These data suggest that dopamine is a good candidate as an endogenous triggering and sustaining transmitter for the Limax feeding motor program.
陆生软体动物大蛞蝓大脑和口腔神经节内的一个神经系统，在体内和体外通过发出摄食运动程序（FMP）对唇部化学刺激作出反应。我们已对大蛞蝓的大脑和口腔神经节进行化学分析，以寻找参与控制FMP表达的神经递质。在大脑神经节的细胞簇和神经纤维网中发现了多巴胺，浓度为62皮摩尔/神经节；这类含多巴胺的细胞中有很大一部分投射到唇部。口腔神经节含有几个小的多巴胺能细胞，神经纤维网中有大量多巴胺；测得的浓度为10皮摩尔/神经节。在体外将10⁻⁷ M至3×10⁻⁶ M的外源性多巴胺施加于大脑和口腔神经节，可兴奋一个自主活动的唾液腺运动神经元（FB），并抑制一个自主活动的分泌运动神经元（BSN）。3×10⁻⁶ M至3×10⁻⁵ M的多巴胺浓度可触发FMP输出，多巴胺浓度越高触发概率增加。ADTN和SK&F38393是该系统中的强效激动剂，而麦角新碱是唯一发现有效的强效拮抗剂；所测试的神经阻滞剂均无效。因此，大蛞蝓系统显示出与脊椎动物D1受体相似的激动剂反应，但其拮抗剂结合特性似乎具有与脊椎动物受体截然不同的要求。外源性5-羟色胺的作用与多巴胺不同；5-羟色胺兴奋BSN和几个口腔运动神经元，不能引发同步的运动程序循环，且不能被麦角新碱有效阻断。这些数据表明，多巴胺很可能是大蛞蝓摄食运动程序的内源性触发和维持递质。
