Name: analysis of gene expression changes in the rat hippocampus after deep brain stimulation of the anterior thalamic nucleus
Uploaded: 2015-03-08T15:00:00
Description: Watch this Scientific Journal Video about Analysis of Gene Expression Changes in the Rat Hippocampus After Deep Brain Stimulation of the Anterior Thalamic Nucleus at JoVE.com

We are grateful for the support of the NREF foundation.

NOTE: Ethics Statement: All procedures discussed in this manuscript are in accordance with the NIH guidelines for Animal Research (Guide for the Care and Use of Laboratory Animals) and are approved by the Harvard Medical School IACUC Committee.
1. Pre-surgical Preparation
<ol>
	<li>Make sure that all surgical instruments are sterilized by either autoclaving or by cleansing with antiseptic solution and/or ethanol as necessary. Where possible, use sterile disposable equipment such as scalpels,...

Following the landmark work by Benabid et al. in using deep brain stimulation to treat Parkinson&#8217;s disease and essential tremor, the DBS surgical technique has been investigated with much interest over the past decade to treat many neurological disorders6,10,43. DBS studies targeting various neuro-anatomical regions of the brain circuitry are currently performed by many groups to address major neuronal diseases and are in various stages of clinical trials. Stimulation of the subthalamic nucleus ...

The history behind the development of Deep Brain Stimulation as a neurosurgical technique dates back to the 1870s when the possibility of electrically stimulating the brain circuitry was explored2. The use of chronic high-frequency stimulation as treatment for neuronal disorders started in the 1960s3. Later in the 1990s with the advent of chronic implantation DBS electrodes4-6, the number of neuronal disorders that were treated by DBS continued to increase. Deep Brain Stimulation was first used in the United States as a treatment for essential tremor6. Today the surgery is used widely to treat neuronal disorders that are currently untreatable by pharmacological intervention. DBS is currently used to treat movement disorders of Parkinson&#8217;s disease and dystonia7-9. Alzheimer&#8217;s type dementia, Huntington&#8217;s disease, epilepsy, pain and neuropsychiatric diseases such depression, OCD, Tourette&#8217;s syndrome and addiction are some of the conditions amenable to treatment by DBS10-12. While DBS surgery is FDA approved for treating Parkinson&#8217;s disease, dystonia and essential tremor, the use of DBS for treating other conditions mentioned above are in various stages of lab and clinical studies offering much promise to patients13,14.
Clinically, DBS surgery is performed in two stages. The first stage involves surgically positioning the DBS electrodes at the targeted anatomical location using a combination of radiological positioning, CT, MRI as well as microelectrode readings for enhanced precision. The second stage involves implanting a pulse generator in the patient&#8217;s upper chest and installing extension leads from the scalp to the pulse generator. Based on the neurological condition, several programming schemes for the pulse generator have been standardized and will be used to deliver the desired voltage. The final voltage is reached in a stepwise fashion so as to receive the best clinical response with minimal voltage15. However, in our studies, unlike the chronic DBS implants used clinically, for the sake of simplicity, we have resorted to studying a one-time high frequency stimulation (for 1 hr) in our animal models.
Part of our group&#8217;s research focuses on investigating the use of DBS surgery for treatment-refractory epilepsy. Stereotactic surgical approaches using high frequency stimulation has been explored by many others as an effective option to treat medically-refractory epilepsy which constitutes about 30% of all incidences of epilepsy10,16,17. Cerebellar stimulation targeting the cortical surface as well as the deep cerebellar nuclei have been used in the past as targets to treat epilepsy10,18,19. In addition, hippocampus stimulation has also been tried but with mixed results20,21. Some of the other investigated DBS targets for epilepsy include the cerebral cortex, thalamus, subthalamic nucleus and vagus nerve8. However, following results from several studies in the past few years, the anterior thalamic nucleus (ATN) has emerged as the most common DBS target for epilepsy treatment10,22. Based on knowledge about neuroanatomical circuitry and findings from animal models, several studies have focused on the therapeutic effect of deep brain stimulation of the ATN in treating epilepsy 23-26. The ATN is part of the limbic circuit and is located in the region of the brain that affects seizure frequency. Studies by Hamani et al., have tested the efficacy of ATN-DBS in a pilocarpine induced epilepsy model and found that bilateral ATN stimulation prolonged latencies for pilocarpine-induced seizures and status epilepticus24. Furthermore, high frequency stimulation of the ATN was found to reduce seizure frequency in a pentylenetetrazol (PTZ) model of epilepsy25,27-29. Lee et al., have reported a mean reduction in seizure frequency by about 75% upon chronic deep brain stimulation of the ATN in treating refractory partial epilepsy30.
A recent clinical study on treatment-refractory epilepsy has shown promising results after DBS surgery targeting the anterior thalamic nucleus (ATN)22. A multicenter randomized clinical trial with 110 patients undergoing bilateral DBS of the ATN for treatment refractory epilepsy (SANTE trial) indicated a drop in seizure frequency by approximately 40%31. The results from this study also hinted on a delayed optimal anti-epileptic effect observed at 2-3 months post surgery. Further studies by Toda et al., corroborated with these findings where they demonstrated neurogenesis happening at a later time post DBS (days 3-5) in animal models1. In addition, Encinas et al., have reported hippocampal neurogenesis in the adult mouse dentate gyrus after high frequency stimulation of the ATN32. Previous studies33-35 have reported declining hippocampal neurogenesis in certain epileptic cases such as chronic temporal lobe epilepsy and an association with learning deficits, memory impairment and spontaneous recurrent motor seizures. Furthermore, there was a reduction in neural stem cell progenitor factors such as FGF2 and IGF-1 in the chronically epileptic hippocampus in animal models 33. Considering this, interventional strategies such as DBS that show an augmentation of neurogenesis in the dentate gyrus are exciting avenues for research. These findings have encouraged us to explore further deeply into the mechanism underlying neurogenesis post-DBS treatment for epilepsy. We have targeted the ATN both unilaterally (data not reported) as well as bilaterally (in representative results) and seen elevated neurotrophin (BDNF) expression in the rat dentate gyrus. Our current hypothesis is that BDNF expression initiates a gene expression cascade that culminates in neurogenesis that translates to the anti-epileptic effect of DBS surgery. In this paper, we present our methods for DBS surgery targeting the ATN in rats followed by gene expression analysis as an attractive approach to study the mechanism underlying the benefits of DBS.

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			<td height="25" style="height:25px;width:236px;">Deep Brain Stimulation Surgery</td>
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			<td>Catalog No.&#160;</td>
			<td>Comments</td>
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			<td height="20" style="height:20px;">Stereotactic frame</td>
			<td>Kopf Instruments</td>
			<td>Model 900</td>
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			<td>Dremmel</td>
			<td>7700, 7.2 V</td>
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			<td>372610</td>
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			<td>Patterson Veterinary</td>
			<td>07-803-6637</td>
			<td>Schedule III Controlled Substance, procurement, use and storage according to institutional rules</td>
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			<td>Patterson Veterinary</td>
			<td>07-808-1947</td>
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			<td>Patterson Veterinary</td>
			<td>07-850-2280</td>
			<td>Schedule III Controlled Substance, procurement, use and storage according to institutional rules</td>
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			<td>ConMed Corporation</td>
			<td>8035</td>
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			<td>Harvard Apparatus</td>
			<td>72-3333</td>
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			<td>Sterile, use for Anesthesia administration intraperitoneally</td>
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			<td>Sterile, use for Analgesia administration subcutaneously</td>
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			<td>305761</td>
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			<td>Fisher Scientific</td>
			<td>S25309B</td>
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			<td>Fisher Scientific</td>
			<td>19-898-350</td>
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			<td>Medtronic</td>
			<td>Model 3628</td>
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			<td>Rhodes Medical Instruments, CA</td>
			<td>SNEX100x-100mm</td>
			<td>Electrodes are platinum, concentric and bipolar</td>
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			<td height="20" style="height:20px;">Betadine (Povidone-Iodine)&#160;</td>
			<td>PDI</td>
			<td>S23125</td>
			<td>Single use swabsticks, use for sterilizing the scalp before making incision&#160;</td>
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			<td colspan="2" height="25" style="height:25px;">&#160;Brain Dissection and Hippocampal tissue isolation</td>
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			<td>Vendor Name</td>
			<td>Catalog No.&#160;</td>
			<td>Comments</td>
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			<td height="20" style="height:20px;">Acrylic Rodent Brain Matrix</td>
			<td>Electron Microscopy Sciences</td>
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			<td>www.emsdiasum.com</td>
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			<td>V W R</td>
			<td>55411-050</td>
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			<td>Clauss</td>
			<td>18039</td>
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			<td>Codman Classic</td>
			<td>34-4098</td>
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			<td>Electron Microscopy Sciences</td>
			<td>72957-06</td>
			<td>Use for removing the brain from the skull and for handling during dissection</td>
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			<td height="20" style="height:20px;">Phosphate Buffered Saline&#160;</td>
			<td>Boston Bioproducts</td>
			<td>BM-220</td>
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			<td colspan="2" height="25" style="height:25px;">&#160;RNA Extraction and cDNA Preparation</td>
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			<td>Fisher Scientific</td>
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			<td>Fisher Scientific</td>
			<td>A416-1</td>
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			<td>Thermo Scientific</td>
			<td>R0561</td>
			<td></td>
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			<td height="20" style="height:20px;">Dnase I Kit</td>
			<td>Ambion</td>
			<td>AM1906</td>
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		<tr height="20">
			<td height="20" style="height:20px;">Superscript First Strand Synthesis Kit</td>
			<td>Invitrogen</td>
			<td>11904-018</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;">Tabletop Microcentrifuge</td>
			<td>Eppendorf</td>
			<td>5415D</td>
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		<tr height="20">
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			<td height="25" style="height:25px;">&#160;Quantitative PCR</td>
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			<td>Catalog No.&#160;</td>
			<td>Comments</td>
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			<td>Qiagen</td>
			<td>204143</td>
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			<td height="20" style="height:20px;">Custom Oligos</td>
			<td>Invitrogen</td>
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			<td height="20" style="height:20px;">PCR Plates (96 wells)</td>
			<td>Denville Scientific</td>
			<td>C18080-10</td>
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			<td height="20" style="height:20px;">Optical Adhesive Sheets</td>
			<td>Thermo Scientific</td>
			<td>AB1170</td>
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			<td height="20" style="height:20px;">Nuclease free Water</td>
			<td>Thermo Scientific</td>
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			<td height="20" style="height:20px;">Real Time PCR Machine</td>
			<td>Applied Biosystems</td>
			<td>7500</td>
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analysis of gene expression changes in the rat hippocampus after deep brain stimulation of the anterior thalamic nucleus

Deep brain stimulation (DBS) surgery, targeting various regions of the brain such as the basal ganglia, thalamus, and subthalamic regions, is an effective treatment for several movement disorders that have failed to respond to medication. Recent progress in the field of DBS surgery has begun to extend the application of this surgical technique to other conditions as diverse as morbid obesity, depression and obsessive compulsive disorder. Despite these expanding indications, little is known about the underlying physiological mechanisms that facilitate the beneficial effects of DBS surgery. One approach to this question is to perform gene expression analysis in neurons that receive the electrical stimulation. Previous studies have shown that neurogenesis in the rat dentate gyrus is elicited in DBS targeting of the anterior nucleus of the thalamus1. DBS surgery targeting the ATN is used widely for treatment refractory epilepsy. It is thus of much interest for us to explore the transcriptional changes induced by electrically stimulating the ATN. In this manuscript, we describe our methodologies for stereotactically-guided DBS surgery targeting the ATN in adult male Wistar rats. We also discuss the subsequent steps for tissue dissection, RNA isolation, cDNA preparation and quantitative RT-PCR for measuring gene expression changes. This method could be applied and modified for stimulating the basal ganglia and other regions of the brain commonly clinically targeted. The gene expression study described here assumes a candidate target gene approach for discovering molecular players that could be directing the mechanism for DBS.

Figures 1A and 1B show the relative expression of BDNF and GABRD relative to the control gene &#946;-actin. BDNF, a neurotrophin is often associated with neuroprotective effects in many neuronal diseases38-41. It is therefore interesting to analyze the expression profile of BDNF in response to stimulation of the ATN which yields therapeutic benefits to epileptic patients. In Figure 1A which shows the gene expression profile of BDNF across the indicated time-po...

Watch this Scientific Journal Video about Analysis of Gene Expression Changes in the Rat Hippocampus After Deep Brain Stimulation of the Anterior Thalamic Nucleus at JoVE.com

Analysis of Gene Expression Changes in the Rat Hippocampus After Deep Brain Stimulation of the Anterior Thalamic Nucleus

The mechanism underlying the therapeutic effects of Deep Brain Stimulation (DBS) surgery needs investigation. The methods presented in this manuscript describe an experimental approach to examine the cellular events triggered by DBS by analyzing the gene expression profile of candidate genes that can facilitate neurogenesis post DBS surgery.

Deep brain stimulation (DBS) surgery, targeting various regions of the brain such as the basal ganglia, thalamus, and subthalamic regions, is an effective ...

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