Background

many decades have seen the conceptual evolution of the neurosciences paralleled by numerous groundbreaking methodological advancements that have paved the means for precise measurement and observation of the animal brain. Today ’ s cognition of the central nervous system and its specific functions have benefited from mod imaging techniques such as the MRI, multielectrode electrophysiology, and optogenetics, but unarguably the most authentic and long-established techniques involve an invasive exploration of different brain regions, known as the stereotaxic neurosurgery. Derived from the Greek stereo, meaning upstanding and three-dimensional, and tactos, meaning arranged and oriented, the condition “ stereotaxy ” denotes the concept of placement in space, as it is used in the context of neurosurgery today. Stereotaxy was founded on the necessity for developing a method acting that could allow precise lesioning in specific areas of the mind, a motivation that exists all the more today, with portray technological and scientific advancements in the field of neuroscience. The invention of stereotaxic procedures in animals arose in 1887 when Sir Victor Horsley and R.H. Clarke acknowledged the need for such a method in probing the connections of the cerebellum in the rhesus putter. Clarke designed a “ stereotaxic device ” that allowed the stable placement and care of the animal ’ south principal within a cubic system of coordinates modeled in horizontal, sagittal, and frontlet planes. Using this device, along with a microtome that could cut through the cranial bone, Clarke and Horseley were able to elaborate models showing the positions of specific mind regions relative to each other, american samoa well as to the airfoil of the skull. furthermore, the stereotaxic invention besides allowed for an intervene lesioning electrode, minimizing the loss of bone tissue and extra weave damage to fundamental cerebral regions. additionally, more than furthering discoveries in the neurosciences, stereotaxic procedures besides have meaning value in human neurosurgery in the medical sic. Before the development of magnetic resonance visualize, stereotaxic neurosurgery required extensive radiological equipment for the visual image of the mind, american samoa well as the control condition and position of instruments used in encroaching procedures. Arteriography and ventriculography were besides then used the reduction of possible risks that could arise from imprecise surgical manipulation. homo neurosurgery methods have since then become increasingly sophisticate with the second coming of modern and computerize stereotaxic approaches, yet their foundations are hush securely rooted in pioneer numeric-based visualize. today, stereotaxic operation applications in humans include treatment of centrifugal disorders, biopsies of tumoral pathologies and interstitial radiotherapies, and discussion of other conditions such as hydrocephalus and epilepsy. Given these all-important contributions, the significance of stereotaxic methods remains evocative with nowadays ’ sulfur scientific community.

The necessity of animal experiment for the progress of research, however, continues to be a sensitive subject of argument among scholars, given the salient function that immanent moral attitudes play. It must be noted that the use of animals in research, peculiarly in the neurosciences, has been an essential reference of discovery ; a lot is known about the anatomy, physiology, and demeanor of rodents, the applications of which enormously contribute to the sympathize of human biota and demeanor. Thus, given these justifications, the scientific community is intelligibly in agreement as to the acceptance of animal experiment, for vitamin a long as no valid option is so far to be presented. Stereotaxic surgery among rodents and all animals, in general, is therefore kept in nonindulgent adhesiveness to rigorous ethical consideration, through effective execution of regulative principles and guidelines of the represent committees in unlike countries. The nuance of procedures, materials, and engineering has henceforth been a necessity in the area of animal research, particularly in the applications of stereotaxic neurosurgery in rodents. Increasing cognition on the optimization of surgical procedures, a well as heightened public awareness on animal rights and benefit issues and the implementation of stern legislation call for standardization of practices in stereotaxic operation ( Formari et al., 2012 ). These demands have prompted the development of devices and protocols, to be discussed in the take after sections, which researchers can employ for successful experiment .

Introduction

Rodents are one of the most widely-employed experimental animals in neurobehavioral research due to a number of reasons. To a great degree, the popularity of rats and mouse as experimental animals can be attributed to the undeniable public toilet and practicality that they offer. particularly, because of their little size, rodents are manageably easy to house, shop, and take care of. Additionally, the usage of transgenic animals and the handiness of pure genic rodent lines further the utility of rodents in the experimental setting ( Messier et al., 1998 ). numerous rodent models have, consequently, unsurprisingly been implemental in the research and treatment of assorted homo diseases american samoa good as in the agreement of the different functions of the human brain. The fundamentals of stereotaxic surgery begin with the preoperative phase, which involves the confirmation of the rodents ’ health status and the cooking and sterilization of surgical equipment. The diverse methods of pain reduction during and after the surgical procedure along with the importance of adopting proper anesthetic protocols are besides taken into circumstance ( Ferry et al., 2014 ). Further, the success of stereotaxic operating room is not complete without following standardize protocols for post-surgical care a well as the comprehensive protocols for histology and autopsy procedures. Because the stereotaxic border on requires anatomical reference and functional expertness along with demand mathematical position of different genius structures of the rodent, readiness in these areas is key to successful experiment. importantly, the basics of operating room are besides necessary for achieving the good results, in detail, the diverse methods related to anesthesia, analgesia, and asepsis. A combination of knowledgeability and expertness, equally well as the properly come of training and the right usage of stereotaxic equipment, are consequently needed in successfully executing stereotaxic surgical procedures

Stereotaxic Equipment
Parts of the Stereotaxic Apparatus

The main consistency of the stereotaxic apparatus consists of a u-shaped stereotaxic frame fixed upon a floor plate. Three mechanical elements attached to the frame permit for the accurate placement of an electrode or cannula holder along three extraneous axes, fore and backward, up and down, and slope to side. The localization of the electrode or cannula holder is manipulated using three adjustable micrometer Vernier screw drives. Two laterally adjustable ear bars and a height-adjustable incisor bar are besides fixed onto the central processing unit to hold the head of the animal in an exact military position. The ear bars center the head parallel to the anteroposterior axis of the stereotaxic frame, while the incisor prevention determines the flat of inclination of the animal ’ second head in the “ flat-skull position. ” The two reference point points on the animal ’ randomness skull ; the bregma and lambda, are kept in the lapp horizontal flat using the incisor bar. The chief body of the stereotaxic apparatus consists of a u-shaped stereotaxic frame fixed upon a foundation plate. Three mechanical elements attached to the frame allow for the accurate placement of an electrode or cannula holder along three orthogonal axes, forward and backward, up and down, and slope to side. The placement of the electrode or cannula holder is manipulated using three adjustable micron Vernier screw drives. Two laterally adjustable auricle bars and a height-adjustable incisor bar are besides fixed onto the mainframe to hold the head of the animal in an demand position. The ear bars center the head parallel to the anteroposterior bloc of the stereotaxic frame, while the incisor barroom determines the flat of inclination of the animal ’ second head in the “ flat-skull position. ” The two address points on the animal ’ mho skull ; the bregma and lambda, are kept in the same horizontal plane using the incisor measure .

The Stereotaxic Surgical Procedure

much preparation is necessity before stereotaxic surgery can successfully take place. first, animals must be in thoroughly health, as evidenced by their appearance and general demeanor on the day of operation. The maintenance, planning, and sterilization of surgical equipment is of prime importance, along with the handiness and verification of anesthetics that shall be used for the procedure. The usage of anesthesia and extensive awareness of its different effects in varying stages is samara to pain management during pre-, intra-, and postoperative treatment. Further, in the usage of anesthesia, much importance is placed on monitoring vital signs, particularly in achieving the proper depth of sedation by checking respective reflexes, angstrom well as maintaining general homeostasis, body temperature, and proper hydration while the animal is sedated. finally, the rodent must undergo shearing in order to eliminate hair and facilitate the disinfection of the skin. Once the stereotaxic frame-up is cook, the rodent may be placed onto the apparatus, on a thermostatically-controlled heat blanket, and fitted with a rectal temperature probe. Simply, the research worker needs to adhere to the distinctive pre-and-post-operative checklist .

Setting up the Animal in the Stereotaxic Instrument

The animal is considered ready to be placed on the stereotaxic apparatus once the proper depth of surgical anesthesia is reached, as indicated by even breathe and a characteristic loss of reflexes. placement of the Ear Bars, Tooth/Incisor Bar, and Nose Bar In securing the animal onto the set-up, one of the two auricle bars must first be fixed in the legal document. then, the head of the animal is lightly steered so that the ear canal is guided towards the pay back auricle bar. The forefront is then horizontally maneuvered sol that the gratuity of the browning automatic rifle is positioned behind the aural bone spur. Once the bar is in set, a soft cluck will be heard. One must be careful to distinguish the sound from a brassy snatch, characteristic of a possible tear eardrum if the browning automatic rifle is inserted excessively far. then, the second ear bar is guided into the early ear canal. Once both ear bars are by rights placed, the head of the animal will only be able to shift in an Antero- and retroflex fashion. once the ear bars are properly in position, the subject ’ s head may then be aligned with the center of the stereotaxic frame. The mouth of the animal is opened, and the chattel tooth bar is slide behind its upper incisors. The read/write head of the animal is then gently pulled forth so that the tooth legal profession may slide and click into its chastise place. The concluding step is locking the beak in station with the use of the nose barroom. The oral sex is immobilized by fixing the nose browning automatic rifle ’ s setscrew at the proper place setting, providing sufficiently firm and stable pressure on the snout. In this manner, no head motion shall be possible during the surgical routine .

Preparation of the Operation Zone and Draping

After securing the animal in place, the skin on which the incision will be made is then disinfected by washing with aseptic gauze soaked with antiseptic soap, alcohol, and an antiseptic solution. The standard moisten procedure involves centrifugal strokes, away from the incision site towards the periphery. The gauze must not touch the edge of the shave zone. The surgical drapes are used for the alimony of asepsis after the operation zone is cleaned. The curtain should cover the entire animal, and can even extend to the adjacent areas, in order to widen the surface of the sterile zone .

Incision and Exposure of the Cranial Surface

A scalpel fitted with a new blade is used to incise the scalp. Precise scalpel cover is necessary, involving all layers of peel. The linear incision must start slenderly in front man of center horizontal surface and continue back or caudally to approximately 0.5 curium behind the ear bars.

Stereotaxic Landmarks

once the incision is made, the suture lines of the four bone plates of the skull surface must be visibly identified in order to locate the two reference points correctly ; the bregma and lambda. The bregma pertains to the intersection of the sagittal and frontal sutures at the level of the snout, whereas the lambda, named for its resemblance to the greek letter lambda, is a point located on the midplane and at the base of the triangulum formed by the lambdoid and sagittal sutures. Once the stereotaxic landmarks have been identified, the operator may carry on with the procedure, beginning with taking the coordinates of the two reference point points using the peak of the legal document .

Applications

Stereotaxic procedures have been around for a hanker time, and up until immediately have much to contribute to the methodological principles of research in the neurosciences. The importance of cognition acquired through stereotaxic surgery on rodents and other experimental animals is of considerable order of magnitude, given the successful extrapolation of findings to research on homo biology and behavior. Beyond furthering cognition, the impact of stereotaxy extends to the symptomatic treatment of motor disorders in humans such as Parkinson ’ second disease, arsenic well as biopsies of tumoral pathologies and interstitial radiotherapies, and the treatment of other illnesses like epilepsy. different techniques are used for different inquiry objectives, and these include experimental procedures in vivo for the activation or deactivation of certain brain regions or vector systems, permanent wave selective lesioning, functional neuroanatomy through the consumption of tracers, and acute or chronic measurements or recordings ( Ferry et al., 2014 ). Inducing Lesions One lotion of stereotaxic procedures on experimental animals lies in the investigation of behavioral functions mediated by unlike mind regions, by implementing an ablation of function. Procedures such as these involve experimentally induce lesions of especial mind regions and studying the resulting deficits in function. There are plenty of ways to damage or deplete a mind structure or vector system through stereotaxic neurosurgery, such as electrolysis, transection, aspiration, radio frequency, injection of excitotoxins, or by ball-shaped or focal ischemia through the practice of devascularization, photo-irradiation, vessel blockage, or vasoconstrictor agents. additionally, stereotaxic neurosurgery can besides be used for the impermanent inactivation of a mind social organization, through microinjection of muscimol, tetrodotoxin, lidocaine, or sense organ antagonists at the target system. Lesioning via electrolysis was first accomplished by Duncan et al., 1975 in which dopamine-containing boldness terminals were unilaterally destroyed through the use of unipolar electrolytic lesions of the medial forebrain bundle. Transection, meanwhile, is another authentic lesioning method that basically involves cutting across target brain structures. Milner and Amaral ( 1984 ) successfully created transections across projections of the septal complex to the hippocampus, in the attack to investigate the being of a ventral septohippocampal nerve pathway. furthermore, some researchers argue that excitotoxic lesioning remains the most authentic and effective method acting that guards against damage to local anesthetic glial cells or traversing steel fibers ( Kirby et al., 2012 ). across-the-board loss of brain cells surrounding target genius structures can handily be avoided by careful practice of excitotoxic focal injection ( Jarrard, 2002 ). Researchers from UCLA and MIT ( Kirby et al., 2012 ) besides successfully developed a stereotaxic method acting allowing for excitotoxic lesions of specific genius areas through an infusion of N-methyl-D-aspartate ( NMDA ). specifically, the infusion of NMDA into the brain results in the excitotoxic death of nearby neurons. The established protocol can besides be used to infuse early biological compounds, such as viral vectors, and the implantation of more permanent osmotic pumps for prolong photograph. furthermore, stereotaxic surgery besides allows for the foreplay of certain brain regions through a number of techniques. These include electric stimulation through a nonselective activation of a heterogenous population of neurons, stimulation of NMDA-receptor-bearing neurons through microinjection of NMDA, and laser application succeeding transfection of modify gene sequences ( Buchen, 2010 ). Through a combination of genetics, virology, and optics, optogenetics has provided a tool with which researchers can quickly activate or inactivate specific groups of neurons within particular neural circuits in a highly precise manner that is unachievable through early more traditional methods ( Buchen, 2010 ). Tracing of Neural Pathways Retrograde and anterograde tracing, which involve the infusion of such substances as pale yellow source agglutinin-conjugated horseradish peroxidase or Fast blue ( Milner and Amaral, 1984 ), enable the hound of neural pathways and particular brain structures as necessitated by some stereotaxic procedures. Sampling Techniques In addition, stereotaxy besides allows for sampling techniques in rodents, such as microdialysis. In vivo measurements ( measurements in a be organism ) can be done through the concentration of extracellular neuromediators by microdialysis, voltammetry ( Li et al., 2006 ), and electro potentials. The process of microdialysis provides quantification of assorted substances in lineage and tissue, including neurotransmitters and neuropeptides, enzyme natural process, electrolytes, and hormones deoxyadenosine monophosphate well as the monitor of biochemical and physiologic effects of pharmaceutical agents. furthermore, the method besides allows for more in-depth observation of drug effects on extracellular levels of endogenous substances ( Li et al., 2006 ). digression from its sampling function, microdialysis besides permits the infusion of certain substances into the mind and spinal cord. The stereotaxic operation would involve the insertion of a microdialysis probe with intake and wall socket tubes for perfusion and sample collection into the fluent or tissue compartment ( Zapata et al., 2009 ). Rodent Models of Human Diseases Another extremely useful application of stereotaxic lesioning is the elaboration of rodent models of human diseases. For exemplify, a model involving platelet collection with regard to cerebral ischemia was developed by Watson et al., 1985 as an undertake to investigate the widespread incidence of human stroke cases due to vascular thrombosis. Jumping off on well-established findings on throw cases, Bergeron ( 2003 ) successfully yielded a photothrombotic cortical stroke model by inducing photochemical cortical lesions in the scab brain using stereotaxic surgical procedures. Particularly, a minimally invasive protocol for creating a model of permanent focal ischemia was developed through the function of photochemical cortical lesions. Stem-Cell Transplantation ultimately, stereotaxic procedures are besides involved in practices of stem-cell transplant. The discovery of neural stalk cells has opened the door to the possibility of regenerative therapy for many illnesses of the central aflutter system, such as Parkinson ’ mho disease. Their properties of self-renewal and multipotency provide the answer to global degeneration or dysfunction, as characterized by the loss of discrete nervous populations either isolated or dispersed in specific regions of the genius. neural root cell transplant in the rodent genius allows for further probe into its remedy electric potential for the discussion of certain CNS diseases ( Lee et al., 2008 ). The importance of stereotaxy is in full emphasized by the numerous possible applications that it endlessly presents. The implications of stereotaxic principles during a technologically-advanced time only add to the many possibilities that this branch of skill and these twist set of methods can continue to offer.

Care and Storage

Stereotaxic instruments require allow manage and guardianship for continued manipulation. After every surgical process, the stereotaxic apparatus along with reclaimable instruments should be cleaned, decontaminated, and sterilized. The instruments must inaugural be washed with soap and urine after use, thoroughly dried, and then autoclaved. More sensitive materials such as cannulae, obturators, and electrodes should be carefully decontaminated or autoclaved, taking into retainer their detail technical tolerances. In cleaning the stereotaxic apparatus, cotton swabs or paper towels soaked with an antiseptic solution of 70 % ethyl alcohol are applied to the frame, ear, intrude and tooth bars, and verniers, a well as on the inflame slog, rectal temperature probe, and workbench. Upon repositing, stereotaxic equipment must undergo regular contraceptive maintenance and service of equipment, depending on their frequency of usage. Measures such as these should efficaciously maintain the instrument ’ mho preciseness, a well as prevent the possible stereotaxic error from free or unfirm components .

References
  1. Bergeron, M. (2003). Inducing photochemical cortical lesions in rat brain. Current protocols in Neuroscience, 9-16.
  2. Buchen, L. (2010). Neuroscience: Illuminating the brain. Nature News, 465(7294), 26-28.
  3. Duncan, R. J. S., Sourkes, T. L., Dubrovsky, B. O., & Quik, M. (1975). Activity Of Aldehyde Dehydrogenase, Aldehyde Reductase, And Acetylcholine Esterase In Stritatum Of Rats Bearing Electrolytic Lesions Of The Medial Forebrain Bundle. Journal of neurochemistry, 24(1), 143-147.
  4. Ferry, B., Gervasoni, D., & Vogt, C. (2014). Stereotaxic neurosurgery in laboratory rodent: handbook on best practices. Springer Science & Business.
  5. Fornari, R. V., Wichmann, R., Atsak, P., Atucha, E., Barsegyan, A., Beldjoud, H., … & Roozendaal, B. (2012). Rodent stereotaxic surgery and animal welfare outcome improvements for behavioral neuroscience. Journal of visualized experiments: JoVE, (59).
  6. Jarrard, L. E. (2002). Use of excitotoxins to lesion the hippocampus: update. Hippocampus, 12(3), 405-414.
  7. Messier, C., Émond, S., & Ethier, K. (1999). New techniques in stereotaxic surgery and anesthesia in the mouse. Pharmacology Biochemistry and Behavior, 63(2), 313-318.
  8. Milner, T. A., & Amaral, D. G. (1984). Evidence for a ventral septal projection to the hippocampal formation of the rat. Experimental brain research, 55(3), 579-585.
  9. Lee, J. P., McKercher, S., Muller, F. J., & Snyder, E. Y. (2008). Neural stem cell transplantation in mouse brain. Current Protocols in Neuroscience, 3-10.
  10. Li, Y., Peris, J., Zhong, L., & Derendorf, H. (2006). Microdialysis as a tool in local pharmacodynamics. The AAPS journal, 8(2), E222-E235.
  11. Watson, B.D., Dietrich, W.D., Busto, R., Wachtel, M.S., and Ginsberg, M.D. 1985. Induction of reproducible brain infarction by photochemically initiated thrombosis. Ann. Neurol. 17:497-504.
  12. Zapata, A., Chefer, V. I., & Shippenberg, T. S. (2009). Microdialysis in Rodents. Current Protocols in Neuroscience / Editorial Board, Jacqueline N. Crawley … [et Al.], CHAPTER, Unit 7.2. http://doi.org/10.1002/0471142301.ns0702s47

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