Bahls F H, Emery D G, Haydon P G
Department of Zoology and Genetics, Iowa State University, Ames 50011, USA.
Invert Neurosci. 1995;1(2):123-31. doi: 10.1007/BF02331910.
In this study, we have further characterized the morphology and physiology of the neuroglandular synapse between the identified buccal neuron, B4, and the salivary gland of Helisoma. We demonstrate that the coupling coefficient between salivary cells within an individual acinus is approximately 1.0. We also demonstrate that synapses within the salivary gland are located near a superficial muscle layer. We examine the effects of glutamate on the salivary gland and on the B4-salivary gland EPSP. L-glutamate produces a transient, rapid onset depolarization of salivary gland cells. The response is mimicked by high concentrations of L-homocysteic acid, but not by NMDA, L-aspartate, D-glutamate or kainate. The response is blocked by the presence of L- or D-glutamate in the bath, but not by CNQX, DNQX, DGG, D-AP5, or L-AP3. The depolarization is primarily dependent on the presence of calcium in the bathing solution. When either L- or D-glutamate is present in the bathing solution, the amplitude of the B4-salivary gland EPSP is reversibly reduced. The similar pharmacological properties of the response of the salivary gland to glutamate and the B4 epsp indicate that L-glutamate is a strong candidate for the fast excitatory neurotransmitter at the Helisoma neuroglandular synapse.
在本研究中，我们进一步描述了已鉴定的颊神经元B4与椎实螺唾液腺之间神经腺突触的形态和生理特征。我们证明单个腺泡内唾液细胞之间的耦合系数约为1.0。我们还证明唾液腺内的突触位于浅表肌肉层附近。我们研究了谷氨酸对唾液腺以及对B4 - 唾液腺兴奋性突触后电位（EPSP）的影响。L - 谷氨酸可使唾液腺细胞产生短暂、快速起效的去极化。高浓度的L - 高半胱氨酸可模拟该反应，但N - 甲基 - D - 天冬氨酸（NMDA）、L - 天冬氨酸、D - 谷氨酸或 kainate不能模拟。该反应可被浴液中L - 或D - 谷氨酸的存在所阻断，但不能被CNQX、DNQX、DGG、D - AP5或L - AP3阻断。去极化主要依赖于浴液中钙的存在。当浴液中存在L - 或D - 谷氨酸时，B4 - 唾液腺EPSP的幅度会可逆性降低。唾液腺对谷氨酸反应和B4兴奋性突触后电位的相似药理学特性表明，L - 谷氨酸是椎实螺神经腺突触快速兴奋性神经递质的有力候选者。
