Quantitative analysis of the spontaneous activity and response profiles of odorant receptor neurons in larval Xenopus laevis using the cell-attached patch-clamp technique

by Rodi Topci
Doctoral thesis
Date of Examination:2020-06-24
Date of issue:2020-06-19
Advisor:Prof. Dr. Dr. Detlev Schild
Referee:Prof. Dr. Dr. Detlev Schild
Referee:Prof. Dr. Tina Pangrsic
Referee:Prof. Dr. Margarete Schön
Persistent Address: http://dx.doi.org/10.53846/goediss-8051

 

 

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Abstract

English

The scope of this thesis was to investigate the activity of ORNs in larval Xenopus laevis in the absence and presence of adequate stimuli. Acute nose-brain slice preparations of the olfactory epithelium, the olfactory nerves and the anterior part of the brain including the olfactory bulb were used as an experimental approach. The olfactory receptor neurons were incubated with the calcium dye Fluo-8-AM and following Ca2+-imaging enabled the detection of amino acid-sensitive ORNs. Patching the amino acid-sensitive ORNs in the cell-attached voltage clamp mode allowed the recording of both spontaneous and stimulus induced activities. All ORNs (n = 46) showed activity in the absence of obvious stimulus. Thereby, the SFRs of ORNs were constant during recording time but differed across different neurons, ranging from 0.24 to 5.5 APs per second on average (median 1.64/s). Furthermore, it was shown that in almost all ORNs the spontaneous activity was a Poisson process and the SFRs were a good first estimate of the event rate λ. The application of stimuli revealed diverse tuning of ORNs, 3/46 ORN responding to concentrations in the nanomolar range, all of them responding to stimulus concentrations as high as 50 μM. The calculated virtual EC-50 value is 8.8 μM. The post-stimulatory instantaneous frequencies and number of APs covered a range of 3.19 to 59.17 Hz and 13 APs to 135 APs, respectively. The reported results were comparable with studies in other species regarding spontaneous activity and the calculated EC-50 value for ORNs in larval Xenopus laevis. Future studies could investigate the origin and function of spontaneous activity in ORNs and its contribution to olfactory coding in the neuronal network.
Keywords: Xenopus laevis; patch-clamp; sensitivity of odorant receptor neurons; Poisson distribution of spontaneous activity in ORN; spontaneous activity of odorant receptor neurons
 
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