Impact of axon initial segment variability and plasticity onto neuronal excitability in CA1 pyramidal cellDolenc, Jan (Avtor) Kreft, Marko (Mentor) Draguhn, Andreas (Komentor) biologyneurobiologyhippocampuspyramidal cellaxon initial segmentplasticityThe hippocampus is considered to be one of the most thoroughly researched parts of the brain. The primary type of hippocampal nerve cells are pyramidal cells, which make up most of the cells in hippocampal pyramidal layer. In our study we focused on CA1 pyramidal cells, more specifically on the specialized proximal part of their axons, the axonal initiation segment (AIS). The aim of the study was to learn more about the variability of AIS within the CA1 pyramidal layer of the hippocampus, to determine its impact on neuronal excitability and to monitor changes in AIS morphology due to external factors in order to understand its plasticity. Acute mouse brain slices from two genetic lines were used for the experiments: the wild-type Black 6 and the transgenic mouse line, which expressed the fluorescent fusion protein ankyrin G-GFP under the ankG promoter. Our results confirmed that the length of the AIS varies greatly between neurons within the CA1 pyramidal layer of the hippocampus. It has been shown that neurons in the more dorsal parts of the hippocampus have on average longer AIS than neurons located ventrally. It was also determined that the maximum number of action potentials triggered by a single stimulation with a high electric current depends on the length of the AIS. Longer AISs contribute to a greater number of consecutive action potentials. We have shown that even after the death of an organism, spontaneous changes in the length of the AIS occur. In our study we demonstrated how elevated extracellular potassium concentration affects the activity of CA1 pyramidal cells and their AIS. The increased potassium concentration has caused shortening of the AIS and a decrease in their fluorescence intensity.20202020-10-16 07:15:08Magistrsko delo/naloga121564sl