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Novel approaches to explore mechanisms of epileptic seizures - optogenetic and chemogenetic manipulation of hippocampal circuitry

Berglind, Fredrik LU (2016) In Lund University Faculty of Medicine Doctoral Dissertation Series 2016:26.
Abstract
Epilepsy comprises a family of neurological disorders characterized by recurrent seizures, which can be

highly debilitating. Up to 30% of patients with temporal lobe epilepsy, the most common form of the disorder in adults, arising in the hippocampus, cannot be effectively treated by current pharmaceuticals. Novel treatment strategies are highly needed, as well as increased understanding of the hippocampal components and signaling properties involved in the mechanisms of epileptogenesis and induction of seizures, to guide a rational search for such future treatments.

In the present thesis, we have applied optogenetics to study these questions, a technology based on modified microbial membrane channels or pumps that are... (More)
Epilepsy comprises a family of neurological disorders characterized by recurrent seizures, which can be

highly debilitating. Up to 30% of patients with temporal lobe epilepsy, the most common form of the disorder in adults, arising in the hippocampus, cannot be effectively treated by current pharmaceuticals. Novel treatment strategies are highly needed, as well as increased understanding of the hippocampal components and signaling properties involved in the mechanisms of epileptogenesis and induction of seizures, to guide a rational search for such future treatments.

In the present thesis, we have applied optogenetics to study these questions, a technology based on modified microbial membrane channels or pumps that are introduced into target neurons, which can thereafter be activated by light. This is a powerful means of achieving excitatory or inhibitory control over neurons in a target specific manner.

In paper I, we have explored the use of inhibitory optogenetics to attenuate seizures (epileptiform bursts) in acute chemical models in vitro and in vivo. GABAergic inhibition was abolished creating a strong excitatory drive among principal neurons in mainly area CA3 of the hippocampus. Under these conditions, we showed that we could inhibit hypersynchronized bursts by activating the inhibitory chloride pump NpHR.

Repeated neuronal discharges gradually creating a hyperexcitable state in the hippocampal circuitry and presenting with seizure-like afterdischarges, known as the kindling process, is traditionally induced by electrical stimulation. In paper II & III, we showed that similarly, afterdischarges could be generated by repeated optogenetic train stimulation in anaesthetized transgenic mice expressing the excitatory cation channel ChR2. Additionally, we corroborated the well known role of the dentate gyrus is this type of progressive seizure model. Finally, using the chemogenetic novel hyperpolarizing Gi-DREADD receptor, activated by CNO, we could show that inhibiting the dentate gyrus and CA3 contralateral to optogenetic stimulation effectively halted the afterdischarge progression.

The work presented in this thesis reinforces the potential of optogenetic and chemogenetic techniques to explore the mechanistic underpinnings and new treatment options for seizures & epilepsy. (Less)
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author
supervisor
opponent
  • Professor Walker, Matthew, University College London
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Seizure, epileptogenesis, optogenetics, NpHR, ChR2, DREADD, hippocampus, in vivo, mouse
in
Lund University Faculty of Medicine Doctoral Dissertation Series
volume
2016:26
pages
71 pages
publisher
Experimental Epilepsy Group
defense location
Segerfalksalen, BMC A11, Sölvegatan 17, Lund
defense date
2016-02-12 09:15
ISSN
1652-8220
ISBN
978-91-7619-252-8
language
English
LU publication?
yes
id
028e2cba-548b-4fa1-9989-938229537fdd (old id 8565626)
date added to LUP
2016-01-26 14:06:31
date last changed
2017-09-19 14:58:15
@phdthesis{028e2cba-548b-4fa1-9989-938229537fdd,
  abstract     = {Epilepsy comprises a family of neurological disorders characterized by recurrent seizures, which can be<br/><br>
highly debilitating. Up to 30% of patients with temporal lobe epilepsy, the most common form of the disorder in adults, arising in the hippocampus, cannot be effectively treated by current pharmaceuticals. Novel treatment strategies are highly needed, as well as increased understanding of the hippocampal components and signaling properties involved in the mechanisms of epileptogenesis and induction of seizures, to guide a rational search for such future treatments.<br/><br>
In the present thesis, we have applied optogenetics to study these questions, a technology based on modified microbial membrane channels or pumps that are introduced into target neurons, which can thereafter be activated by light. This is a powerful means of achieving excitatory or inhibitory control over neurons in a target specific manner.<br/><br>
In paper I, we have explored the use of inhibitory optogenetics to attenuate seizures (epileptiform bursts) in acute chemical models in vitro and in vivo. GABAergic inhibition was abolished creating a strong excitatory drive among principal neurons in mainly area CA3 of the hippocampus. Under these conditions, we showed that we could inhibit hypersynchronized bursts by activating the inhibitory chloride pump NpHR.<br/><br>
Repeated neuronal discharges gradually creating a hyperexcitable state in the hippocampal circuitry and presenting with seizure-like afterdischarges, known as the kindling process, is traditionally induced by electrical stimulation. In paper II &amp; III, we showed that similarly, afterdischarges could be generated by repeated optogenetic train stimulation in anaesthetized transgenic mice expressing the excitatory cation channel ChR2. Additionally, we corroborated the well known role of the dentate gyrus is this type of progressive seizure model. Finally, using the chemogenetic novel hyperpolarizing Gi-DREADD receptor, activated by CNO, we could show that inhibiting the dentate gyrus and CA3 contralateral to optogenetic stimulation effectively halted the afterdischarge progression.<br/><br>
The work presented in this thesis reinforces the potential of optogenetic and chemogenetic techniques to explore the mechanistic underpinnings and new treatment options for seizures &amp; epilepsy.},
  author       = {Berglind, Fredrik},
  isbn         = {978-91-7619-252-8},
  issn         = {1652-8220},
  keyword      = {Seizure,epileptogenesis,optogenetics,NpHR,ChR2,DREADD,hippocampus,in vivo,mouse},
  language     = {eng},
  pages        = {71},
  publisher    = {Experimental Epilepsy Group},
  school       = {Lund University},
  series       = {Lund University Faculty of Medicine Doctoral Dissertation Series},
  title        = {Novel approaches to explore mechanisms of epileptic seizures - optogenetic and chemogenetic manipulation of hippocampal circuitry},
  volume       = {2016:26},
  year         = {2016},
}