| dc.contributor.advisor | Schild, Detlev Prof. Dr. Dr. | |
| dc.contributor.author | Okom, Camille Inès Alexandra | |
| dc.date.accessioned | 2016-12-19T10:57:56Z | |
| dc.date.available | 2016-12-19T10:57:56Z | |
| dc.date.issued | 2016-12-19 | |
| dc.identifier.uri | http://hdl.handle.net/11858/00-1735-0000-002B-7CE9-A | |
| dc.identifier.uri | http://dx.doi.org/10.53846/goediss-6046 | |
| dc.language.iso | eng | de |
| dc.relation.uri | http://creativecommons.org/licenses/by-nc-nd/4.0/ | |
| dc.subject.ddc | 570 | de |
| dc.title | Structural and functional characterisation of M/T cells using Ca2+ Imaging and Activity Correlation Imaging in dendritic networks of the developing Xenopus brain | de |
| dc.type | doctoralThesis | de |
| dc.contributor.referee | Schild, Detlev Prof. Dr. Dr. | |
| dc.date.examination | 2016-12-09 | |
| dc.description.abstracteng | Olfactory information collected in the nose is conveyed from the axon terminals of olfactory receptor neurons to the dendritic tufts of mitral/tufted (M/T) cells across glutamatergic synapses. These synaptic interactions occur within glomeruli, the spherical neuropil structures where presynaptic and postsynaptic fibres intermingle. The second-order projection
neurons, the M/T cells carry out sensory processing and integration of the olfactory signals. In Xenopus laevis larvae, sensitivity to temperature drops is encoded by a group of receptor neurons terminating a particular glomerulus, called the γ-glomerulus. Interestingly, several studies brought evidence that some M/T cells receive their input from more than one glomerulus. Yet, the implications of such a connectivity in terms of multi-processing and encoding of olfactory information have not yet been investigated. We hypothesised that the multiple glomerular innervation by M/T cells would enable them to collect and integrate both chemical and thermic information. Consequently, Ca2+ imaging experiments performed in olfactory bulb slices revealed that most temperature-sensitive M/T cells also responded to chemical odourants, indicating that the dual-sensitivity of these cells is a
function of their one-to-many glomerular connectivity.
Furthermore, Xenopus M/T cells display upon odourant stimulation three types of temporal activity patterns: activated, inhibited, unresponsive, which corroborate previous research showing that reciprocal and lateral M/T cell inhibition affects odour representations in the rodent bulb. Inhibitory periglomerular and granule cells establish contact with M/T cells through dendrodendritic synapses and constitute a scalable inhibitory lever on M/T cell outputs. In order to test the effect of GABA-mediated inhibition on Xenopus M/T cells, the Ca2+ dynamics of M/T ensembles were compared in the presence or absence of gabazine, a GABA-A receptor antagonist. The blockade of inhibition drastically altered
the patterns of odour responses in M/T cells. Moreover, gabazine did not desynchronise correlated patterns of spontaneous activity across these neurons, but enhanced them. These results demonstrate that GABAergic inhibition of M/T cells drives odour discrimination and contrast enhancement of overlapping odour signals in these neurons. In contrast, it plays a minor role, if any, in the coupling of M/T cells’ baseline activities.
Finally, simultaneous patch-clamp recordings and Ca2+ imaging proved that action potentials (APs) and AP-related Ca2+ signals backpropagate in the dendrites of Xenopus M/T cells. Spontaneous and somatically evoked APs activated Ca2+ channels generating Ca2+ spikes were observed in dendritic branches and glomerular endings. Besides, the cross-correlation analysis of Ca2+ fluctuations along M/T cell dendrites exposed differential activities of dendritic sub-compartments. Early evidence suggests that gabazine enhances
the uniformity of backpropagating spikes along dendrites. | de |
| dc.contributor.coReferee | Fiala, André Prof. Dr. | |
| dc.subject.eng | olfaction, Xenopus, mitral cells, thermosensitivity, inhibition, dendrite, calcium imaging | de |
| dc.identifier.urn | urn:nbn:de:gbv:7-11858/00-1735-0000-002B-7CE9-A-3 | |
| dc.affiliation.institute | Göttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften (GGNB) | de |
| dc.subject.gokfull | Biologie (PPN619462639) | de |
| dc.identifier.ppn | 875159621 | |