Glutamate-mediated synaptic transmission between neuron B4 and salivary cells ofHelisoma trivolvis |
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Authors: | Fredrick H Bahls Dennis G Emery Philip G Haydon |
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Institution: | (1) Department of Zoology and Genetics, Laboratory of Cellular Signaling, 339 Science II, Iowa State University, 50011 Ames, IA, USA |
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Abstract: | 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 ofHelisoma. 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
ofl-homocysteic acid, but not by NMDA,l-aspartate,d-glutamate or kainate. The response is blocked by the presence ofl- ord-glutamate in the bath, but not by CNQX, DNQX, DGG,d-AP5, orl-AP3. The depolarization is primarily dependent on the presence of calcium in the bathing solution. When eitherl- ord-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 thatl-glutamate is a strong candidate for the fast excitatory neurotransmitter at theHelisoma neuroglandular synapse. |
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Keywords: | synapse glutamate Helisoma salivary gland |
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