Schläger, Laura (2018). Ionic currents and intrinsic properties of key interneurons and their influence on network activity in a chain of coupled oscillators. PhD thesis, Universität zu Köln.

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Abstract

Post-inhibitory rebound (PIR) plays an important role in producing rhythmic network activity. By inducing new excitation, following a phase of inhibition it promotes the generation of rhythmic neuronal activity. I investigated this property in identified neurons of the swimmeret system. These neurons are characterized by membrane potential oscillations and create the well-coordinated Power- and Return-Stroke movements of four pairs of swimmerets at the abdomen of crayfish. I isolated the abdominal nervous system and performed current clamp recordings with sharp electrodes at the dendritic aborizations of the neurons. I tested whether the neurons are able to produce a PIR by injecting hyperpolarizing current pulses. All spiking neurons (PSE, RSE, ASCE and DSC) possessed the ability to produce a PIR, which was accompanied by a small sag potential. In contrast, not all neurons of the central pattern generator, IPS, generated a PIR. The only neuron receiving excitatory synaptic input, ComInt1, also produce a PIR. Different ionic currents are shown in various studies to account for the generation of a PIR. Those are the L-type calcium current (ICaL), the hyperpolarization activated cation current (IH), and in some systems the persistent sodium current (INaP). In the following experiments, I investigated the ionic basis of the PIR in the above described neuron groups. I could detect that both ICaL and IH and partially INaP generate PIR responses in the spiking neurons PSE, RSE, ASCE and DSC, while only IH seemed to be involved in generating the PIR in IPS. To test the significance of the identified ionic conductances for generation of rhythmic motor output, I blocked the respective ionic currents individually while monitoring fictive locomotion of the system on the network-, as well as on the single cell level. During this series of experiments also the contribution of the transient potassium current, IA, was investigated by application of 4-AP. Confirming the importance of the above identified currents (ICaL, IH and INaP), all ion channel blockers altered the ability of the entire system to produce a steady motor rhythm. Similar strong effects were observed when blocking IA. These results of this study demonstrate that PIR is an essential mechanism for the neurons in the swimmeret system to induce new excitability after a phase of inhibition. This suggests that PIR plays a crucial role in establishing rhythmic cellular activity. Furthermore, I could show that PIR responses were mediated by different ionic current depending on the neuron group.

Item Type: Thesis (PhD thesis)
Creators:
CreatorsEmailORCID
Schläger, LauraUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-92688
Subjects: Life sciences
Uncontrolled Keywords:
KeywordsLanguage
ionic currentsEnglish
CPGEnglish
crayfishEnglish
Faculty: Faculty of Mathematics and Natural Sciences
Divisions: Faculty of Mathematics and Natural Sciences > Institute for Zoology
Language: English
Date: 2018
Date of oral exam: 3 September 2018
Referee:
NameAcademic Title
Wellmann, CarmenPD. Dr.
Büschges, AngsarProf. Dr.
Refereed: Yes
URI: http://kups.ub.uni-koeln.de/id/eprint/9268

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