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Role of P2X7 receptors during seizure activity in the dentate gyrus
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García Durillo, Mónica (2022) Role of P2X7 receptors during seizure activity in the dentate gyrus. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3878505~S15
Abstract
Thirty percent of the adult population with epilepsy is resistant to commercially available anti-seizure drugs (ASDs). Therefore, there is a need to find new molecular targets to develop new drugs. Purinergic signalling is mediated by purine nucleotides and nucleosides such as ATP and adenosine. While adenosine is an important endogenous anticonvulsant, ATP is an extracellular-signalling molecule able to bidirectionally modulate seizure-activity by activating ionotropic P2X and metabotropic P2Y receptors. Among all P2 receptors, a potential therapeutic role of the P2X7 receptor (P2X7R) in refractory epilepsy has been proposed.
In this thesis we focused our attention on the dentate gyrus (DG) region of the hippocampus since our data showed an overexpression of the P2X7R in the DG after intra-amygdala kainic acid-induced status epilepticus (SE). To pharmacologically study the role of the P2X7Rs in the DG during seizures, we used an in vitro model of refractory SE and three models of acute seizures by incubating hippocampal slices with: 0 mM Mg2+ / 50 M 4-aminopyridine (4-AP) / 1 M 8-cyclopentyl-1,3-dimethylxanthine (8-CPT). Our electrophysiological data showed minor or no effect of the selective P2X7R antagonist A740003 on seizure activity. However, a combination of A740003 with lorazepam delayed the onset of spontaneous seizure-like events (SLEs). In contrast, we observed that a late application of lorazepam (after 60 min of SE-like activity) had a pro-convulsive effect indicative of entry into drug refractory SE. Furthermore, we observed adenosine release from the DG during seizure-activity by enzyme-based biosensor recordings. However, ATP release detection was elusive and technically challenging even when using an ecto-ATPases inhibitor, ARL67156, to prevent ATP hydrolysis.
In addition to pharmacological experiments targeting P2X7Rs, we used P2X7R null and over-expressing mice to study the role of P2X7Rs in seizure activity and ATP and adenosine release during seizure-like activity in the DG. However, electrophysiological and biosensor data revealed little or no differences between mouse genotypes. 17
Finally, our in vitro model of refractory SE did not induce the mRNA upregulation of several pro-inflammatory molecules such as interleukin-1β (Il-1β), the ionized calcium binding adaptor molecule 1 (Iba1) or the tumour necrosis factor alpha (TNFα) measured by RT-qPCR.
Overall, our data confirmed that obtaining an effective anti-seizure effect of lorazepam is time-dependent where a late treatment could even aggravate SLEs. Moreover, even though our data showed a minor or no contribution of P2X7Rs on seizure activity, blocking P2X7R could be considered as an adjunct therapy with lorazepam to treat patients with refractory SE.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QP Physiology R Medicine > RC Internal medicine |
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Library of Congress Subject Headings (LCSH): | Epilepsy, Dentate gyrus, Epilepsy -- Treatment | ||||
Official Date: | September 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Life Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Frenguelli, Bruno G. ; Pankratov, Yuriy | ||||
Extent: | 258 pages : illustrations, charts | ||||
Language: | eng |
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