Assessment of Neurovascular Coupling - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 339

Fig. 1. On the left , a typical ion-sensitive microelectrode is illustrated in which the barrels
are closed with wax ( red ). The two contact wires are marked with “+” and “−” (connected
to the reference and the ion-selective barrel). The tip diameter is only 3 μ m. If a device
with a tip diameter exceeding 25 μ m is inserted into the cortex, the mechanical damage
would lead to SD. On the right , ion and electron distributions of a potassium-selective
microelectrode are shown. The electrode constitutes a galvanic element.

used to make the Ag/AgCl wire sheath. The wire is fi xated within
the tube using cyanacrylate glue. In a similar way, the surface
potential (DC and high-frequency ECoG) can be measured in a
closed cranial window using a simple Ag/AgCl wire of which the
tip is inserted into the artifi cial subdural/subarachnoid space of the
closed window. The Ag/AgCl wire is easily produced by electroly-
sis when two silver wires are placed into physiological NaCl solu-
tion and connected to a battery for 60 s. The subdural DC potential
changes of SD as measured with a Ag/AgCl wire are signifi cantly
smaller than the intracortical DC potential changes as measured
with glass microelectrodes. In the study of Dreier et al. ( 21 ), illus-
trations of the DC potential changes during SD are provided as
measured with the two different approaches.

2.4. Anesthesia

Three types of anesthesia are most frequently used for in vivo studies
on neurovascular coupling and spreading ischemia. In general,
adequate levels of anesthesia have to be accurately controlled. This
is done by continuous monitoring of blood pressure and responses
to tail pinch.
Barbiturate anesthesia : Thiopental-sodium (Trapanal, BYK
Pharmaceuticals, Konstanz, Germany) is a rapid-onset short-acting
barbiturate. It is used at a dose of 100 mg/kg body weight intrap-
eritoneally (i.p.). Thiopental causes cardiovascular and respiratory
depression, which requires artifi cial ventilation and monitoring of
arterial blood pressure. If required, additional lower doses of
thiopental are given (e.g., 25 mg/kg i.p.).