Synaptic Transmission and Modulation in the Autonomic Nervous System

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1. Measurement of the release of transmitters mediating the fast EPSP (glutamate and aspartate), the slow EPSP (noradrenaline) and the slow IPSP (noradrenaline) in the spinal lateral horn cells (cat) : The spontaneous and evoked release of glutamate and aspartate from tissue slices of the lateral hoorn were measured by the gass-mass spectrometry. The release of noradrenaline from the same tissue preparation was measured by a high-pressure liquid chromatography.2. Characterization of the receptors mediating the synaptic potentials in the lateral horn cells (cat) and analysis of the intracellular signal transduction for the slow PSPs : The glutamate receptors responsible for production of the fast EPSP were a non-NMDA type in 70% of the cells and non-NMDA plus NMDA types in 30% of the cells. Most of the fast IPSP were mediated by glycine via glycine receptors, while some of the fast IPSP were mediated by GABA through GABA-A receptors. The slow EPSP and IPSP were evoked by noradrenaline via alpha-1 and alpha-2 adrenoceptors, respectively. The former was associated with closing of Ca-dependent K channels due to activation of protein kinase C, and the latter was accompanied by opening of voltage-independent K channels due to activation of G protein.3. Presynaptic inhibition in the lateral horn cells (cat) : The fast EPSP in these cells were inhibited presynaptically by noradrenaline. This inhibition was due to a lowering of the probability of glutamate release.4. Intracellular signal transduction that produces the slow IPSP in Meissner's neurons of alimental canal (guinea-pig) : It was found that the outward synaptic current evoked by the transmitter noradrenaline in Meissner's neurons were produced not only by opening of K channels triggered by activated G protein but also by activation of Ca-dependent K channels that occurred simultaneously with the former.