Non-restraining EEG radiotelemetry is a valuable methodological approach to record in vivo long-term electroencephalograms from freely moving rodents. This detailed protocol describes stereotaxic epidural and deep intracerebral electrode placement in different brain regions in order to obtain reliable recordings of CNS rhythmicity and CNS related behavioral stages.
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Method Article
Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement
In This Article
Summary
Abstract
Implantable EEG radiotelemetry is of central relevance in the neurological characterization of transgenic mouse models of neuropsychiatric and neurodegenerative diseases as well as epilepsies. This powerful technique does not only provide valuable insights into the underlying pathophysiological mechanisms, i.e., the etiopathogenesis of CNS related diseases, it also facilitates the development of new translational, i.e., therapeutic approaches. Whereas competing techniques that make use of recorder systems used in jackets or tethered systems suffer from their unphysiological restraining to semi-restraining character, radiotelemetric EEG recordings overcome these disadvantages. Technically, implantable EEG radiotelemetry allows for precise and highly sensitive measurement of epidural and deep, intracerebral EEGs under various physiological and pathophysiological conditions. First, we present a detailed protocol of a straight forward, successful, quick and efficient technique for epidural (surface) EEG recordings resulting in high-quality electrocorticograms. Second, we demonstrate how to implant deep, intracerebral EEG electrodes, e.g., in the hippocampus (electrohippocampogram). For both approaches, a computerized 3D stereotaxic electrode implantation system is used. The radiofrequency transmitter itself is implanted into a subcutaneous pouch in both mice and rats. Special attention also has to be paid to pre-, peri- and postoperative treatment of the experimental animals. Preoperative preparation of mice and rats, suitable anesthesia as well as postoperative treatment and pain management are described in detail.
Introduction
Radiotelemetry is a most valuable methodological approach for measuring a variety of behavioral and physiological parameters in conscious, unrestrained animals of various sizes, particularly in the context of EEG, ECG, EMG, blood pressure, body core temperature or activity measurements 1-7. Theoretically, any species can be analyzed using implantable EEG radiotelemetry from laboratory rodents such as mice and rats to cats, dogs, pigs and primates 3,8. Even fish, reptiles and amphibians are subject to radiotelemetric investigation 9. Over the last two decades, implantable EEG radiotelemetry has proven to be valuable in the characterizat....
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Protocol
Ethics Statement: All animal experimentation was performed according to the guidelines of the local and institutional Council on Animal Care (University of Bonn, BfArM, LANUV, Germany). In addition, all animal experimentation was carried out in accordance with superior legislation, e.g., the European Communities Council Directive of 24 November 1986 (86/609/EEC) or individual regional or national legislation. Specific effort is made to minimize the number of animals used and their suffering.
1. Experimental Animals
- Selection of experimental animals and species
- Perform radiotelemetric studies in rodents....
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Results
This section illustrates examples obtained from surface and deep, intracerebral EEG recordings. Initially it should be stated that baseline recordings under physiological conditions are mandatory prior to subsequent recordings following e.g., pharmacological treatment. Such baseline recordings may provide valuable information about functional interdependence of brain rhythmicity with different behavioral states or sleep / circadian rhythmicity. Here, we show examples of recorded .......
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Discussion
Implantable EEG radiotelemetry is of central relevance as it is a non-restraining technique allowing experimental animals to perform their full repertoire of behavior1,3. This is of major interest as the telemetric approach enables not only spontaneous EEG recordings but also recordings under cognitive tasks and circadian analytical setups, such as T-maze, radial maze, water maze, sleep deprivation tasks or whenever an EEG recording is necessary or helpful during complex cognitive or motor activity.
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Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors would like to thank Dr. Christina Ginkel (German Center for Neurodegenerative Diseases, DZNE), Dr. Michaela Möhring (DZNE) and Dr. Robert Stark (DZNE) for assistance in animal breeding and animal health care. This work was financially supported by the Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM) Bonn, Germany.
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| Carprofen (Rimadyl VET - InjektionA2:D43slösung) | Pfizer | PZN 0110208 | 20 ml |
| Binocular surgical magnification microscope | Zeiss Stemi 2000 | 0000001003877, 4355400000000, 0000001063306, 4170530000000, 4170959255000, 4551820000000, 4170959040000, 4170959050000 | |
| Bulldog serrefine | F.S.T. | 18051-28 | 28 mm |
| Cages (Macrolon) | Techniplast | 1264C, 1290D | |
| Cold light source | Schott KL2500 LCD | 9.705 202 | ordered at Th.Geyer |
| Cotton tip applicators (sterile) | Carl Roth | EH12.1 | |
| Dexpanthenole (Bepanthen Wund- und Heilsalbe) | Bayer | PZN: 1578818 | |
| Drapes (sterile) | Hartmann | PZN 0366787 | |
| 70% ethanol | Carl Roth | 9065.5 | |
| 0.3%/3% hydrogene peroxide solution | Sigma | 95321 | 30% stock solution |
| Gloves (sterile) | Unigloves | 1570 | |
| Dental glas ionomer cement | KentDental /NORDENTA | 957 321 | |
| 2% glutaraldehyde solution | Sigma | G6257 | |
| Graefe Forceps-curved, serrated | F.S.T. | 11052-10 | |
| Halsey Micro Needle Holder-Tungsten Carbide | F.S.T. | 12500-12 | 12.5 cm |
| Heat-based surgical instrument sterilizer | F.S.T. | 18000-50 | |
| Heating pad | AEG HK5510 | 520010 | ordered at myToolStore |
| High-speed dental drill | Adeor | SI-1708 | |
| Iris scissors extra thin | F.S.T. | 14058-09 | 9 cm |
| Inhalation narcotic system (isoflurane) | Harvard Apparatus GmbH | 34-1352, 10-1340, 34-0422, 34-1041, 34-0401, 34-1067, 72-3044, 34-0426, 34-0387, 34-0415, 69-0230 | |
| Isoflurane | Baxter 250 ml | PZN 6497131 | |
| Ketamine | Pfizer | PZN 07506004 | |
| Lactated Ringer’s solution (sterile) | Braun | L7502 | |
| Lexar-Baby Scissors-straight, 10 cm | F.S.T. | 14078-10 | 10 cm |
| Nissl staining solution | Armin Baack | BAA31712159 | |
| Non-absorbable suture material 5-0/6-0 (sterile) | SABANA (Sabafil) | N-63123-45 | |
| Covidien (Sofsilk) | S1172, S1173 | ||
| Halsey Needle Holder | F.S.T. | 12001-13 | 13 cm |
| Pads (sterile) | ReWa Krankenhausbedarf | 2003/01 | |
| 0.9% saline (NaCl, sterile) | Braun | PZN:8609255 | |
| Scalpel blades with handle (sterile) | propraxis | 2029/10 | |
| Standard Pattern Forceps | F.S.T. | 11000-12, 11000-14 | 12 cm and 14.5 cm length |
| Steel and tungsten electrodes parylene coated | FHC Inc., USA) | UEWLGESEANND | |
| Stereotaxic frame | Neurostar | 51730M | ordered at Stoelting |
| (Stereo Drive-New Motorized Stereotaxic) | |||
| Tapes (sterile) | BSN medical GmbH & Co. KG | 626225 | |
| TA10ETA-F20 | DSI | 270-0042-001X | Radiofrequency transmitter 3.9 g, 3.9 g, 1.9 ml, input voltage range ± 2.5 mV, channel bandwidth (B) 1 - 200 Hz, nominal sampling rate (f) 1,000 Hz (f = 5B) temperature operating range 34 - 41 °C warranted battery life 4 months |
| TL11M2-F20EET | DSI | 270-0124-001X | Radiofrequency transmitter 3.9 g, 1.9 ml, input voltage range ± 1.25 mV, channel bandwidth (B) 1 - 50 Hz, nominal sampling rate (f) 250 Hz (f = 5B) temperature operating range 34 - 41 °C warranted battery life 1.5 months |
| Tissue Forceps- 1x2 Teeth 12 cm | F.S.T. | 11021-12 | 12 cm length |
| Tungsten carbide iris scissors | F.S.T. | 14558-11 | 11.5 cm |
| Vibroslicer 5000 MZ | Electron Microscopy Sciences | 5000-005 | |
| Xylazine (Rompun) | Bayer | PZN: 1320422 |
References
- Kramer, K., et al. The use of radiotelemetry in small laboratory animals: recent advances. Contemp Top Lab Anim Sci. 40, 8-16 (2001).
- Kramer, K., et al. The use of telemetry to record electrocardiogram and hea....
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