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Evaluation of the Functional Roles of TRPA1 Homologs, Painless and dTRPA1, in Chemical Nociception in Drosophila

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abstract
The detection of harmful chemical irritants is important for the avoidance of potential tissue-damaging and life threatening compounds. There are multiple physiological systems that exist to detect these irritants, and one specific target of these compounds is the TRPA1 channel. Drosophila possess four evolutionary homologs of mammalian TRPA1, two of which are painless and dTRPA1. These are thought to be involved in chemical nociception, though the specific role of painless in the behavioral aversion to the compound, allyl isothiocyanate, is disagreed upon. We have analyzed the behavioral phenotypes of painless and dTRPA1 mutants using the proboscis extension reflex (PER) and two-choice capillary feeding assays, both of which indicated the requirement for each channel in the aversion to AITC. Expression patterns of these two channels were evaluated to determine if there was any overlap in expression between painless and dTRPA1. We observed a lack of colocalization in the adult CNS. Cell populations were further defined by the identification of cell specific markers. Subsets of painless- and dTRPA1-expressing cells coexpress the neuropeptides, DH31 and leucokinin, respectively. Additionally, we specifically expressed tetanus toxin, which blocks synaptic transmission, to verify that these drivers were capturing the aversive circuit. However, it is unclear whether painless and dTRPA1 are acting independently or in combination. To assess painless and dTRPA1 cell excitability, the GCaMP transgene was utilized to observe changes in calcium levels. Both painless- and dTRPA1-expressing cells exhibited significant changes in fluorescence following the application of AITC. Notably, it was determined that activation via AITC occurred in a direct manner following the ectopic expression of painless and dTRPA1 in AKH cells and evaluation of GCaMP responses for painless in a dTRPA1 mutant background. Collectively, these results suggest that each channel is acting independently to detect irritants and that both are required for behavioral aversion.
subject
Chemical nociception
Drosophila
dTRPA1
Irritants
Neural circuits
painless
contributor
Shoaf, Madison Lee (author)
Silver, Wayne L (committee chair)
Johnson, Erik C (committee member)
McCauley, Anita K (committee member)
date
2012-06-12T08:36:00Z (accessioned)
2012-12-12T09:30:07Z (available)
2012 (issued)
degree
Biology (discipline)
embargo
2012-12-12 (terms)
identifier
http://hdl.handle.net/10339/37290 (uri)
language
en (iso)
publisher
Wake Forest University
title
Evaluation of the Functional Roles of TRPA1 Homologs, Painless and dTRPA1, in Chemical Nociception in Drosophila
type
Thesis

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