Stereotaxic (also known as stereotactic) techniques are used in multidisciplinary neuroscience research labs worldwide. Stereotaxic procedures are well established in rodent models to study the brain, neuronal functions / communication and to manipulate neural function.
Stereotaxy is used to:
- achieve access to an animal’s brain
- accurately target sites (dependent on setting the correct coordinates)
- enable reliable and repeatable positioning
The anaesthetised animal’s head is stabilised and fixed in a pre-defined position on a stereotaxic frame. Stereotaxic coordinates that correspond to a reference stereotaxic brain atlas are used to target a precise region of the brain. The bregma and lambda landmarks on the animal’s skull are used as anatomical markers for stereotaxic surgery.
Both rat and mouse brain atlases are available with accurate three-dimensional coordinates of brain structures and anatomical information for stereotaxy. Australian anatomist and neuroscientist Professors Charles Watson and George Paxinos first published “The Rat Brain in Stereotaxic Coordinates” in 1982.The Paxinos and Watson Rat Brain Atlas has become the most trusted source of accurate coordinates and anatomical information in laboratories throughout the world. It has been cited over 60,000 times, making it one of the most cited publications in neuroscience.
Stereotaxy Applications in Research:
Stereotaxic surgery in rodent models can target deep structures within the brain. Research includes:
- creating lesions at targeted sites
- targeted virus and tracer injections
- implanting neurobiological probes into specific brain regions for later studies in conscious animals
Stereotaxic intracranial injections can be used to introduce genetically-engineered viruses and/or to alter expression of a specific gene in a targeted brain area in rodents. Stereotaxic injection of lentivirus was used along with behavioural tests to study how genetic factors modulate mouse behaviour (McSweeney and Mao, 2015).
Stereotaxic surgery is used to implant probes in specific regions of the rodent brain for microdialysis studies. The implanted microdialysis probes are used for infusing substances into the brain or spinal cord and to collect dialysate containing substances such as neurotransmitters, peptides, hormones, electrolytes, drugs for subsequent analysis. “Accurate and reproducible implantation into the area to be sampled is crucial for micro-dialysis experiments. Stereotaxic coordinates, however, can differ depending upon the strain, age, and sex of an animal.” Zapata et al. (2009)
Hence pilot studies using stereotaxic atlases to find precise stereotaxic coordinates is essential.
Gieger et al. (2008) demonstrated stereotaxic implantation of guide cannulas targeting specific sites in the rat brain and showed how to insert and implant a microdialysis probe. Stereotaxic surgeries allow placement of implants such as cannulae and sealed chambers for long term access to the rodent brain for injections and recordings.
EEG Studies – Stereotaxic implantation of (hardwired or wireless) EEG Electrodes:
Stereotaxy enables recording of high-quality EEGs from both the surface and deep intracerebral structures for studying seizure disorders in neurological diseases, traumatic brain injury, epilepsy and sleep disorders. Medlej et al. describe long term continuous EEG monitoring of tethered rats after stereotaxic surgery for implantation of epidural or depth EEG electrodes.
Published by David Kopf Instruments, “Kopf Carrier” #95 provides a detailed methodology for the stereotaxic implantation of multiple screw electrodes, used for recording multichannel EEG data from the surface of an adult rat brain. Kopf Carrier #95 is available on request to all researchers:
Stereotaxic surgery was used by Goldey et al. (2014) for implanting removable cranial windows in mice for long-term imaging studies.
There are a large field of choices when it comes to stereotaxic equipment. There are a small but growing number of manufacturers, each having a position in the market.
Stereotaxic devices from David Kopf Instruments are considered by many researchers as the most accurate and reliable choice for stereotaxic surgeries and are adaptable for use with a wide variety of small animals. The range includes modular accessories allowing for expansion of instrument capabilities, including additional/future applications. These instruments are easy to use, durable and provide precise and repeatable setup for stereotaxic surgeries.