The work was funded by a fellowship from the
Institute for Translational Medicine and Therapeutics, and a training
grant from the Institute for Medicine and Engineering (T32HL007954) at
the University of Pennsylvania and the Marlene L. Cohen and Jerome H.
Fleisch Scholar Grant at the University of Connecticut Health Center
(LHS) and NIH NS-029331(FAW).

1. Preparation of equipment
<ol>
<li>Wipe down the stereotaxic frame and pump with 75% ethanol to minimize bacterial contamination.</li>
<li>Sterilize Hamilton syringe and fused silica needle. 
Note: If chemical sterilization is used, be sure to rinse several times in sterile water before use.</li>
<li>Wipe surface of paraffin wax paper with 75% ethanol and allow to dry.</li>
</ol>
2. Preparation of mouse for injection
Note: Have mice delivered to your animal facility at least 7 days before the surgery to allow them to acclimate to the new environment and reduce stress.
<ol>
<li>Weigh mouse for pre-operative baseline.</li>
<li>Induce anesthesia with 30% Oxygen, 70% Nitrous oxide, and 4% Isoflurane until unresponsive to tail pinch</li>
<li>Inject mouse with buprenorphine 0.1mg/kg intraperitoneally for post-operative analgesia</li>
<li>Shave scalp</li>
<li>Coat eyes with sterile petroleum jelly</li>
<li>Prepare scalp with betadine x 3 wipes, then allow scalp to dry</li>
<li>Make 1 cm midline sagittal incision of scalp using sterile surgical scalpel 
Note: A generous incision will allow complete exposure of skull landmarks.</li>
<li>Shave 1 cm of ventral surface of tail beginning 1 cm from base and prepare with betadine x 3 wipes</li>
<li>Place mouse on stereotaxic frame 
Note: It is important to ensure mouse is secure in the frame with surface of skull parallel with the base of the frame, with excellent exposure of bregma and at least 3 mm to the right of bregma.</li>
</ol>
3. Intracerebral hemorrhage surgery 
Notes: During the entire surgery the mouse is anesthetized with 30% Oxygen, 70% Nitrous oxide, and 1-3% Isoflurane, continuously maintained at 37 &plusmn; 0.5&deg;C using a thermistor-controlled heating pad and monitored by rectal thermometer.
<ol>
<li>Attach sterile 27 g needle on 1 cc syringe on frame.</li>
<li>Adjust stereotaxic arm until needle is exactly over bregma.</li>
<li>Adjust arm so that needle is at +2.5 mm lateral to bregma and lower to surface of skull.</li>
<li>Manually rotate syringe to make burr hole on surface of skull while applying gentle downward movement of frame- taking care not to completely perforate skull.</li>
<li>Remove needle and complete burr hole manually with syringe/needle 
Note: Completing the burr hole by hand allows for immediate recognition when you have perforated the inner table of skull and minimizes risk of inadvertently pushing needle into brain parenchyma.</li>
<li>Make transverse incision on ventral surface of tail using sterile surgical blade and allow 2-3 large drops of arterial blood to fall onto paraffin wax paper. Then quickly stop bleeding with pressure using sterile gauze.</li>
<li>Withdraw 17 &mu;L blood into Hamilton syringe and place syringe on pump.</li>
<li>Adjust stereotaxic arm to point 5&deg; medially relative to vertical axis.</li>
<li>Carefully adjust stereotaxic arm so that tip of the needle is over the burr hole in skull and then lower needle 3.5 mm.</li>
<li>Wait 2 minutes then withdraw the needle 0.5 mm (so that tip is 3 mm deep)</li>
<li>Wait 5 minutes to allow the brain to re-expand around the needle and minimize risk of blood refluxing up the needle insertion track during injection.</li>
<li>Inject blood 1 &mu;L/minute for 7.5 &mu;L.</li>
<li>Wait 5 minutes to allow initial blood clotting and for tissue shifts to occur to minimize elevations in intracranial pressure.</li>
<li>Inject the remaining 7.5 &mu;L at 1 &mu;L/minute</li>
<li>Allow needle to remain in place for 25 minutes to allow for blood clotting 
Note: Failure to wait for blood clotting will result in blood refluxing up the needle insertion site when withdrawing the needle</li>
<li>Slowly withdraw the needle and immediately rinse with hot water to prevent any residual blood in the needle from clotting and ensure reusability of needle.</li>
<li>Remove the mouse from the frame and close the tail and scalp incisions with veterinary surgical glue.</li>
<li>Turn off anesthesia.</li>
<li>Allow to mouse to awaken while being continuously warmed with free access to moistened food.</li>
<li>Return mouse to cage with littermates when fully awake. Place wet food pellet on the bottom of cage to help animals in access to food. </li>
</ol>
4. Representative results:
<img src="/files/ftp_upload/2618/2618fig1.jpg" alt="Figure 1"/> Figure 1. Coronal section of mouse brain 15 minutes after ICH surgery. Immediately after sacrifice the brain was inspected for ICH success based on gross inspection of a coronal section at the needle insertion site. Hemorrhages that tracked down to the base of the brain, up the needle track past the corpus callosum, or into the ventricles were deemed unsuccessful and that mouse was eliminated from all analyses. Overall ICH success rates were 75-85% in 50 mice with 0% mortality.
<img src="/files/ftp_upload/2618/2618fig2.jpg" alt="Figure 2"/> Figure 2. Cylinder testing demonstrates left hemiparesis after right basal ganglia ICH. (A) Sample mouse rear after ICH surgery. Note the placement of only the right forelimb on the wall of the cylinder after left basal ganglia ICH. (B) Graph of cylinder testing 1 results from cohort of mice after ICH surgery (n=5) compared to sham (n=4). Sham mice had all procedures except blood injection (needle was inserted into brain). Each mouse was placed in a 12-cm diameter clear glass cylinder and observed for 20 rears. The initial placement of the forelimbs on the wall of the cylinder was scored per rear. Subsequent movements (such as lateral exploration) were not scored until the mouse returned to the ground and the next rear scored. The laterality index was calculated as (# right forelimb placements on the side of the cylinder - # left forelimb placements)/(# right + # left + # both), where 0 indicated no forelimb preference and 1 indicated only the right forelimb was used.

<ol>
	<li>Hua, Y., Schallert, T., Keep, R. F., Wu, J., Hoff, J. T., Xi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavioral+Tests+After+Intracerebral+Hemorrhage+in+the+Rat.">Behavioral Tests After Intracerebral Hemorrhage in the Rat.</a> Stroke. 33, 2478-2484 (2002).</li><li>James, M., Warner, D., Laskowitz, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preclinical+Models+of+Intracerebral+Hemorrhage:+A+Translational+Perspective.">Preclinical Models of Intracerebral Hemorrhage: A Translational Perspective.</a> Neurocritical Care. 9, 139-152 (2008).</li><li>Foerch, C., Arai, K., Jin, G., Park, K. -. P., Pallast, S., van Leyen, K., Lo, E. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Model+of+Warfarin-Associated+Intracerebral+Hemorrhage.">Experimental Model of Warfarin-Associated Intracerebral Hemorrhage.</a> Stroke. 39, 3397-3404 (2008).</li><li>Nakamura, T., Xi, G., Hua, Y., Schallert, T., Hoff, J. T., Keep, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracerebral+hemorrhage+in+mice:+model+characterization+and+application+for+genetically+modified+mice.">Intracerebral hemorrhage in mice: model characterization and application for genetically modified mice.</a> Journal of Cerebral Blood Flow and Metabolism. 24, 487-494 (2004).</li><li>Rynkowski, M. A., Kim, G. H., Komotar, R. J., Otten, M. L., Ducruet, A. F., Zacharia, B. E., Kellner, C. P., Hahn, D. K., Merkow, M. B., Garrett, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+mouse+model+of+intracerebral+hemorrhage+using+autologous+blood+infusion.">A mouse model of intracerebral hemorrhage using autologous blood infusion.</a> Nat. Protocols. 3, 122-128 (2008).</li><li>Wang, J., Fields, J., Dor&#233;, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+development+of+an+improved+preclinical+mouse+model+of+intracerebral+hemorrhage+using+double+infusion+of+autologous+whole+blood.">The development of an improved preclinical mouse model of intracerebral hemorrhage using double infusion of autologous whole blood.</a> Brain Research. 1222, 214-221 (2008).</li><li>Zhao, X., Sun, G., Zhang, J., Strong, R., Song, W., Gonzales, N., Grotta, J. C., Aronowski, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hematoma+resolution+as+a+target+for+intracerebral+hemorrhage+treatment:+Role+for+peroxisome+proliferator-activated+receptor+&#947;+in+microglia/macrophages.">Hematoma resolution as a target for intracerebral hemorrhage treatment: Role for peroxisome proliferator-activated receptor &#947; in microglia/macrophages.</a> Annals of Neurology. 61, 352-362 (2007).</li></ol>

No conflicts of interest declared.

This surgical model of intracerebral hemorrhage in mice using autologous tail artery blood results in a reproducible model of spontaneous basal ganglia hemorrhage. An ICH model in mice offers the advantage of the availability of transgenic animals to investigate pathophysiology; however, their small size makes neurosurgical procedures more technically difficult than in larger animals. 
The collagenase model and the autologous blood injection model are two well-established models of experiment...

Stereotaxic frame for mouse neurosurgery (Stoelting, 51925)
Microinfusion pump and processor (UMP-3 and Micro4, World Precision Instruments, Sarasota, FL)
Mouse warmer (Stoelting, 50300)
Inhalational mouse anesthesia (Braintree Scientific, EZ-AF9000)
25 &mu;L gastight borosilicate Hamilton syringe with coated plunger and no needle 
(Hamilton company, Reno, NV, 1702RN syringe: 765401, ferrule: 30949, spacer: 30946)
fused silica needle cut to 2 cm length (Hamilton, 17739) 
*note Hamilton syringe and fused silica needle may be reused for multiple surgeries if sterilized prior to each surgery. These materials are crucial to avoid blood clotting.
Sterile surgical gloves
Surgical gown, bonnet and mask
Betadine
75% ethanol
sterile 27 g needle (single use)
sterile 1 cc syringe (single use)
sterile surgical blade
Cidex
sterile water
buprenorphine and isoflurane
sterile gauze
paraffin wax paper squares
Veterinary surgical glue (Vetbond, 3M, St. Paul, MN)

autologous blood injection to model spontaneous intracerebral hemorrhage in mice

Investigation of the pathophysiology of injury after intracerebral
hemorrhage (ICH) requires a reproducible animal model. While ICH
accounts for 10-15% of all strokes, there remains no specific
effective therapy. The autologous blood injection model in mice
involves the stereotaxic injection of arterial blood into the basal
ganglia mimicking a spontaneous hypertensive hemorrhage in man. The
response to hemorrhage can then be studied in vivo and the
neurobehavioral deficits quantified, allowing for description of the
ensuing pathology and the testing of potential therapeutic agents. The
procedure described in this protocol uses the double injection
technique to minimize risk of blood reflux up the needle track, no
anticoagulants in the pumping system, and eliminates all dead space
and expandable tubing in the system.

Watch this Scientific Journal Video about Autologous Blood Injection to Model Spontaneous Intracerebral Hemorrhage in Mice at JoVE.com

Autologous Blood Injection to Model Spontaneous Intracerebral Hemorrhage in Mice

The autologous blood injection model of intracerebral hemorrhage in mice described in this protocol uses the double injection technique to minimize risk of blood reflux up the needle track, no anticoagulants in the pumping system, and eliminates all dead space and expandable tubing in the system.

Investigation of the pathophysiology of injury after intracerebral
hemorrhage (ICH) requires a reproducible animal model.  While ICH
accounts for 10-15% ...

autologous-blood-injection-to-model-spontaneous-intracerebral

Research

JoVE Journal

Neuroscience

14.7K Views.  University of Connecticut Health Center. The autologous blood injection model of intracerebral hemorrhage in mice described in this protocol uses the double injection technique to minimize risk of blood reflux up the needle track, no anticoagulants in the pumping system, and eliminates all dead space and expandable tubing in the system.

Video: Autologous Blood Injection to Model Spontaneous Intracerebral Hemorrhage in Mice

Modeling Intracerebral Hemorrhage in Mice: Injection of Autologous Blood or Bacterial Collagenase

Spontaneous intracerebral hemorrhage (ICH) defines a potentially life-threatening neurological malady that accounts for 10-15% of all stroke-related hospitalizations and for which no effective treatments are available to date1,2. Because of the heterogeneity of ICH in humans, various preclinical models are needed to thoroughly explore prospective therapeutic strategies3. Experimental ICH is commonly induced in rodents by intraparenchymal injection of either autologous blood or bacterial collagenase4. The appropriate model is selected based on the pathophysiology of hemorrhage induction and injury progression. The blood injection model mimics a rapidly progressing hemorrhage. Alternatively, bacterial collagenase enzymatically disrupts the basal lamina of brain capillaries, causing an active bleed that generally evolves over several hours5. Resultant perihematomal edema and neurofunctional deficits can be quantified from both models. In this study, we described and evaluated a modified double injection model of autologous whole blood6 as well as an ICH injection model of bacterial collagenase7, both of which target the basal ganglia (corpus striatum) of male CD-1 mice. We assessed neurofunctional deficits and brain edema at 24 and 72 hr after ICH induction. Intrastriatal injection of autologous blood (30 &mu;l) or bacterial collagenase (0.075U) caused reproducible neurofunctional deficits in mice and significantly increased brain edema at 24 and 72 hr after surgery (p&lt;0.05). In conclusion, both models yield consistent hemorrhagic infarcts and represent basic methods for preclinical ICH research.

Clinically relevant animal models of intracerebral hemorrhage (ICH) are needed to extend our knowledge of hemorrhagic stroke and to examine novel therapeutic strategies. In this study, we describe and evaluate two ICH models that implement unilateral injections of either autologous whole blood or bacterial collagenase into the basal ganglia (corpus striatum) of mice.

Spontaneous intracerebral hemorrhage (ICH) defines a potentially life-threatening neurological malady that accounts for 10-15% of all stroke-related ...

Medicine

A Murine Model of Subarachnoid Hemorrhage

In this video publication a standardized mouse model of subarachnoid hemorrhage (SAH) is presented. Bleeding is induced by endovascular Circle of Willis perforation (CWp) and proven by intracranial pressure (ICP) monitoring. Thereby a homogenous blood distribution in subarachnoid spaces surrounding the arterial circulation and cerebellar fissures is achieved. Animal physiology is maintained by intubation, mechanical ventilation, and continuous on-line monitoring of various physiological and cardiovascular parameters: body temperature, systemic blood pressure, heart rate, and hemoglobin saturation. Thereby the cerebral perfusion pressure can be tightly monitored resulting in a less variable volume of extravasated blood. This allows a better standardization of endovascular filament perforation in mice and makes the whole model highly reproducible. Thus it is readily available for pharmacological and pathophysiological studies in wild type and genetically altered mice.

A standardized mouse model of subarachnoid hemorrhage by intraluminal Circle of Willis perforation is described. Vessel perforation and subarachnoid bleeding are monitored by intracranial pressure monitoring. In addition various vital parameters are recorded and controlled to maintain physiologic conditions.

In this video publication a standardized mouse model of subarachnoid  hemorrhage (SAH) is presented. Bleeding is induced by endovascular Circle of  Willis ...

Intrastriatal Injection of Autologous Blood or Clostridial Collagenase as Murine Models of Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a common form of cerebrovascular disease and is associated with significant morbidity and mortality. Lack of effective treatment and failure of large clinical trials aimed at hemostasis and clot removal demonstrate the need for further mechanism-driven investigation of ICH. This research may be performed through the framework provided by preclinical models. Two murine models in popular use include intrastriatal (basal ganglia) injection of either autologous whole blood or clostridial collagenase. Since, each model represents distinctly different pathophysiological features related to ICH, use of a particular model may be selected based on what aspect of the disease is to be studied. For example, autologous blood injection most accurately represents the brain&#39;s response to the presence of intraparenchymal blood, and may most closely replicate lobar hemorrhage. Clostridial collagenase injection most accurately represents the small vessel rupture and hematoma evolution characteristic of deep hemorrhages. Thus, each model results in different hematoma formation, neuroinflammatory response, cerebral edema development, and neurobehavioral outcomes. Robustness of a purported therapeutic intervention can be best assessed using both models. In this protocol, induction of ICH using both models, immediate post-operative demonstration of injury, and early post-operative care techniques are demonstrated. Both models result in reproducible injuries, hematoma volumes, and neurobehavioral deficits. Because of the heterogeneity of human ICH, multiple preclinical models are needed to thoroughly explore pathophysiologic mechanisms and test potential therapeutic strategies.

Preclinical models of intracerebral hemorrhage are utilized to mimic certain aspects of clinical disease. Thus, mechanisms of injury and potential therapeutic strategies may be explored. In this protocol, two models of intracerebral hemorrhage are described, intrastriatal (basal ganglia) injections of autologous blood or collagenase.

Intracerebral hemorrhage (ICH) is a common form of cerebrovascular disease and is associated with significant morbidity and mortality. Lack of effective ...

Double Direct Injection of Blood into the Cisterna Magna as a Model of Subarachnoid Hemorrhage

Among strokes, subarachnoid hemorrhage (SAH) consecutive to the rupture of a cerebral arterial aneurysm represents 5-9% but is responsible for about 30% of the total stroke-related mortality with an important morbidity in terms of neurological outcome. A delayed cerebral vasospasm (CVS) may occur most often in association with a delayed cerebral ischemia. Different animal models of SAH are now being used including endovascular perforation and direct injection of blood into the cisterna magna or even the prechiasmatic cistern, each exhibiting distinct advantages and disadvantages. In this article, a standardized mouse model of SAH by double direct injection of determined volumes of autologous whole blood into the cisterna magna is presented. Briefly, mice were weighed and then anesthetized by isoflurane inhalation. Then, the animal was placed in a reclining position on a heated blanket maintaining a rectal temperature of 37 &#176;C and positioned in a stereotactic frame with a cervical bend of about 30&#176;. Once in place, the tip of an elongated glass micropipette filled with the homologous arterial blood taken from carotid artery of another mouse of the same age and gender (C57Bl/6J) was positioned at a right angle in contact with the atlanto-occipital membrane by means of a micromanipulator. Then 60 &#181;L of blood was injected in the cisterna magna followed by a 30&#176; downward tilt of the animal for 2 minutes. The second infusion of 30 &#181;L of blood into the cisterna magna was performed 24 h after the first one. The individual follow-up of each animal is carried out daily (careful evaluation of weight and well-being). This procedure allows a predictable and highly reproducible distribution of blood, likely accompanied by intracranial pressure elevation that can be mimicked by an equivalent injection of an artificial cerebral spinal fluid (CSF), and represents an acute to mild-model of SAH inducing low mortality.

We described in this protocol a standardized subarachnoid hemorrhage (SAH) mouse model by a double injection of autologous whole-blood into the cisterna magna. The high degree of standardization of the double-injection procedure represents a middle-to-acute model of SAH with relative safety regarding mortality.

Among strokes, subarachnoid hemorrhage (SAH) consecutive to the rupture of a cerebral arterial aneurysm represents 5-9% but is responsible for about 30% ...

Massive Pontine Hemorrhage by Dual Injection of Autologous Blood

We provide a protocol to establish a massive pontine hemorrhage model in a rat. Rats weighing about 250 grams were used in this study. One hundred microliters of autologous blood was taken from the tail vein and stereotaxically injected into the pons. The injection process was divided into 2 steps: First, 10 &#181;L of blood was injected into a specific location, anteroposterior position (AP) -9.0 mm; lateral (Lat) 0 mm; vertical (Vert) -9.2 mm, followed by a second injection of the residual blood located at AP -9.0 mm; Lat 0 mm; Vert -9.0 mm with a 20-minute interval. The balance beam test, limb placement test, and the modified Voestch neuroscore were used to evaluate neurological function. Magnetic Resonance Imaging (MRI) was used to assess the volume of hemorrhage in vivo. The symptoms of this model were in line with patients with massive pontine hemorrhage.

We present a protocol to establish a massive pontine hemorrhage model in a rat via dual injection of autologous blood.

We provide a protocol to establish a massive pontine hemorrhage model in a rat. Rats weighing about 250 grams were used in this study. One hundred ...

Pre-Chiasmatic, Single Injection of Autologous Blood to Induce Experimental Subarachnoid Hemorrhage in a Rat Model

Despite advances in treatment over the last decades, subarachnoid hemorrhage (SAH) continues to carry a high burden of morbidity and mortality, largely afflicting a fairly young population. Several animal models of SAH have been developed to investigate the pathophysiological mechanisms behind SAH and to test pharmacological interventions. The pre-chiasmatic, single injection model in the rat presented in this article is an experimental model of SAH with a predetermined blood volume. Briefly, the animal is anesthetized, intubated, and kept under mechanical ventilation. Temperature is regulated with a heating pad. A catheter is placed in the tail artery, enabling continuous blood pressure measurement as well as blood sampling. The atlantooccipital membrane is incised and a catheter for pressure recording is placed in the cisterna magna to enable intracerebral pressure measurement. This catheter can also be used for intrathecal therapeutic interventions. The rat is placed in a stereotaxic frame, a burr hole is drilled anteriorly to the bregma, and a catheter is inserted through the burr hole and placed just anterior to the optic chiasm. Autologous blood (0.3 mL) is withdrawn from the tail catheter and manually injected. This results in a rise of intracerebral pressure and a decrease of cerebral blood flow. The animal is kept sedated for 30 min and given subcutaneous saline and analgesics. The animal is extubated and returned to its cage. The pre-chiasmatic model has a high reproducibility rate and limited variation between animals due to the pre-determined blood volume. It mimics SAH in humans making it a relevant model for SAH research.

Subarachnoid hemorrhage continues to carry a high burden of mortality and morbidity in man. To facilitate further research into the condition and its pathophysiology, a pre-chiasmatic, single injection model is presented.

Despite advances in treatment over the last decades, subarachnoid hemorrhage (SAH) continues to carry a high burden of morbidity and mortality, largely ...

Modeling Neonatal Intraventricular Hemorrhage Through Intraventricular Injection of Hemoglobin

Source: Miller, B. A., et al. <a href="https://app.jove.com/v/63345">Modeling Neonatal Intraventricular Hemorrhage Through Intraventricular Injection of Hemoglobin.</a> J. Vis. Exp. (2022).
This video demonstrates a method to generate a rat model of neonatal intraventricular hemorrhage. In this procedure, an anesthetized rat pup is injected with hemoglobin into the lateral ventricle of the brain. The hemoglobin causes oxidative stress and releases heme, simulating intraventricular hemorrhage. The resulting damage to brain tissues, driven by reactive oxygen species and inflammatory cytokines, leads to ventricular enlargement, a common consequence of intraventricular hemorrhage.

Source: Miller, B. A., et al. Modeling Neonatal Intraventricular Hemorrhage Through Intraventricular Injection of Hemoglobin. J. Vis. Exp. (2022).
This ...

JoVE Encyclopedia of Experiments

Neuropathology

Cerebrovascular Diseases

Establishing a Subarachnoid Hemorrhage Rat Model Induced by Autologous Blood Injection

To place the laser Doppler probe, make a 15-millimeter incision caudally in the midline, starting just anterior to the eyes. After removing the connective tissue and the muscles with forceps, use the end of a sterile cotton swab as a regime to identify the bregma and the coronal sutures.
After placing the armed retractor, place a 25-gauge spinal needle in the stereotaxic frame exactly on the bregma and note the position. Next, remove the needle from the bregma. Move the frame anteriorly by 6.5 millimeters, then replace the needle in the midline to mark the side of drilling.
Drill until the dura mater is identified below the bone. Using straight forceps, gently remove the bone fragments, then fill the cavity with bone wax. Next, 3 to 4 millimeters lateral to the right of the bregma and just anterior to the coronal suture for the laser Doppler, drill another hole taking care not to penetrate the dura mater.
Look for the vessels where the laser Doppler can measure the blood flow. Place the laser Doppler and check the values. A minimum value of 100 flux units is required. If the values remain acceptable after removing the microscope, add 1 drop of glue to fix the probe. Recheck to confirm whether the value is above 80 flux units.
To induce subarachnoid hemorrhage, insert the needle gently through the skull in the midline between the hemispheres until resistance is felt due to the base of the skull. Retract the needle by 1 millimeter to ensure correct placement just anteriorly to the optic chiasm. To ensure the most homogeneous result when injecting the blood, turn the needle clockwise by 90 degrees such that the needle tip points to the right. Then, remove the stiletto.
After a 15-minute equilibration, adjust the level of anesthesia to obtain a mean arterial blood pressure in the range 80 to 100 millimeters of mercury. Then, perform a blood gas analysis to confirm that the pH, partial pressure of carbon dioxide and partial pressure of oxygen are within physiological parameters.
Next, using a 1-milliliter syringe with a blunt 23-gauge needle, withdraw 500 microliters of blood from the tail catheter. To avoid injection of air, fill the dead space of the spinal needle chamber with blood. After adjusting the volume of the blood in the syringe to 300 microliters, connect the syringe to the spinal needle. Then, grasping firmly around the syringe, inject the blood manually to surpass mean arterial pressure. Observe a steep rise in the intracerebral pressure and a concurrent steep fall in the cerebral blood flow.