Biology Reference
In-Depth Information
ear bars and incisor bar) and its position is adjusted so that the
impactor tip just touches the dural surface (zeroing of the tip).
The impactor is withdrawn and then the tip is advanced accord-
ing to the depth of deformation required. The knob is set to
the arm position and the impact is delivered by pressing the
button. In mice the velocity and duration of impact can be
adjusted by turning the respective knobs on the machine. After
the mouse is fixed the impactor is attached and its position is
adjusted so that the tip is at 45° to the dural surface. The
impactor tip is zeroed at the level of the surface of dura (there
is a sensor which alarms when the impactor touches the dural
surface). The impactor is withdrawn and the tip is advanced by
desired length by using the attached Vernier scale. The impact
is then delivered by pressing the button. After securing hemo-
stasis the wound is suture closed using a monofilament 4-0/5-0
prolene or ethilon suture. The parameters used for rats and
mice are given in Table
1
(see Notes 6 and 7).
3. Monitoring: The rectal temperature, mean arterial pressure
(MAP), intracranial pressure (ICP), and brain temperature are
monitored continuously (readings recorder at 30 s intervals).
The rectal thermistor is connected to the monitor or a thermo-
couple thermometer. The brain temperature probe, arterial
pressure transducers, ICP transducer are connected to the
monitor. Microcapnograph requires zero calibration before
each operation. This would require CO
2
(10%) gas cylinder
and N
2
(100%) gas cylinders. After calibration both the respira-
tory rate and ETCO
2
are displayed on the monitor. The tip of
the sensor is placed into a metal cannula provided at the junc-
tion of the “Y” connector or a small hole that is drilled into the
plastic “Y” connector that is used for the mice. A noninvasive
laser Doppler scan (Periscan, PIM3 system, Perimed AB
Stockholm, Sweden) which permits evaluation of microvascu-
lar perfusion in real time is used to measure cerebral blood
flow on both sides. Measurements are expressed as perfusion
units. The values are obtained every 15-30 min during the
monitoring, are compared to the baseline values and are
expressed as percentage of baseline values (see Note 8).
4. Extubation: After the injury and closure of the skin incision,
the animal is transferred along with the heat pad on to the
table surface. The isoflurane is stopped and the rebreathing
bag is emptied. The animal is maintained on 100% oxygen
alone and the reflexes (corneal, pinna, paw, and righting and
escape reflexes) are monitored every minute for 20 min till the
animal is recumbant. Once the animal gains the righting reflex
it is extubated and then oxygen is delivered through a mask
(see Notes 9 and 10).
5. Infusion rates: In rats the venous infusion is given at a rate of
1 ml/h to keep it patent and the arterial infusion rate is
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