Electrotonic and Dye Coupling Between Mammalian Cortical Neurons: Mechanisms of Regulation

摘要

The research has involved studies on neuronal communication in the mammalian brain, and has focused on rapid conducting mechanisms in local neuronal circuits. Most of the work has centered on electrical interactions between cells in the hippocampus, but other research has involved excitatory chemical synaptic transmission in the hypothalmus. The authors have found that intracellular injection of antibodies directed at the liver gap junction polypeptide reduces dye coupling between cultured glial cells. Although antibody injections did not completely block junctional transmission, a similar approach could be useful with hippocampal pyramidal cells for understanding the role that electronic coupling may play in synchronization of neuronal activity. Another major area of research has involved low calcium solutions where chloride was replaced with propionate. These two treatments have been shown to block chemical synaptic transmission and electronic junctions, respectively. The authors have obtained preliminary evidence that synchronous activity can still be obtained in this solution, thus arguing that electrical field effects alone can synchronize the action potentials of hippocampal neurons. In collaboration with Roger Traub at IBM, theoretical studies with a computer model have provided a quantitative conceptual framework for understanding how electrical interactions operate in the hippocampus. Finally, studies with hypothalmic neuroendocrine cells have uncovered a synaptically activated slow depolarization and have provided evidence that excitatory amino acids may be responsible for fast excitatory transmission in the supraoptic nucleus.