Assessment of Neurovascular Coupling - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 343

area and above the canals. The next step is to fill the cavity
surrounded by the wax wall with aCSF. Subsequently, a coverslip is
gently pressed on the wet wax wall to create an even top edge. This
step is crucial if it is planned to close the window by a coverslip later
on. For an open window, the wax wall will be a little bit higher than
for a closed window to ensure an adequate aCSF level in the win-
dow later on. If you like, you can now gently connect the infl ow
tube with a syringe pump which eases fl ushing of the dural surface
with aCSF during the next preparation steps (be cautious not to
move the infl ow tube in the canal while you are connecting it to the
syringe pump). Thereafter, the bone fl ap is removed by pulling it
carefully upwards with a forceps. While you are removing the bone
fl ap, the dural vessels will start to bleed. Bleeding from dural vessels
usually stops spontaneously. The blood is then removed by usage of
a cotton swab alternating with fl ushing of aCSF.
All the following steps are performed under the microscope.
We cauterize the dural vessels before we cut the dura. First, visual-
ize clearly the dural arteriole that you want to cauterize. Then, dry
the surface with a cotton swab (do not let the dura dry for too
long). Subsequently, quickly touch the dry dura with the cauterizer
at the lower rim of the window, where the dural arteriole is visible.
Do not mistake a pial arteriole for a dural one. The cauterization
can be a time-consuming procedure. It should be performed with
great care in order to avoid any damage of the underlying cortex.
After the dural arterioles are cauterized, the dura can be removed.
For this purpose, a small needle tip is carefully bent which is used
for cutting the dura at a small spot (under aCSF). This spot will be
at the right lower corner of the window if you are right-handed
and at the left lower corner if you are left-handed. Any bleeding of
cortical vessels leads to exclusion of the animal from the experi-
ment. After the initial incision, the dura is gently lifted with a fi ne
forceps (using the left hand if you are right-handed). Then, the
incision is carefully enlarged with a micro-scissor (using the right
hand if you are right-handed). This is clearly the most delicate part
of the preparation. If microelectrodes will be inserted, you leave
the window open and should now secure the wax wall and the in-
and outfl ow tubes with dental cement. Then, you are done with
the preparation (Fig. 3 ).
If you plan to build a closed window, do not apply the dental
cement yet. For a closed window, a coverslip is now cut to the
desired size and gently pressed onto the wax wall while the cavity
is fi lled with aCSF. The coverslip should be a bit larger than the
wax wall. The edges of the coverslip are then secured to the wax
wall with a layer of dental cement or cyanacrylate glue. However,
be sure that you have carefully removed all air bubbles from the
artifi cial subdural/subarachnoid space between brain and coverslip
as well as from the infl ow tube and syringe before you apply any
glue or cement. Air bubbles can be very troublesome during the