Emotional and Anxiety Assessments in CNS Disorders - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 246

excluded from analysis. Rodents are freezing on open arm. This would
happen when a noise, movement, or disruption occurs during the
test. Rodents are likely to freeze on the open arm for the majority
of test time. The experimenter should make a note and this rodent
should be excluded from analysis.

1.2. Light/Dark
Box Test

The light/dark test is used to evaluate the anxiety status of rodent.
The light/dark paradigm is based on a confl ict between the innate
aversion to brightly illuminated areas and the spontaneous explor-
atory activity. If given a choice between a large bright compartment
and a small dark compartment, mice spontaneously prefer the dark.
Anxiolytic compounds have been found to increase the total dura-
tion of time spent in bright compartment. Anxiogenic compounds
are observed to work in the opposite way.

The light/dark chamber is similar for mice and rat, except the size.
Typical dimensions are 30 × 23 × 30 cm for light compartment and
15 × 23 × 30 cm for the dark side. Access between light and dark
compartment was provided by a 8 × 6-cm passageway. The
light compartment is transparent and illuminated with a 60-W
bulb positioned 50 cm above. The dark compartment is painted
black and covered by a hinged lid. Transitions between the light and
dark compartment are electronically recorded by photocells or
interruptions of the infrared beams mounted in the chamber.

1.2.1. Materials
and Equipment

The rodents are transferred to behavioral room 1 h prior to the test
for habitation. The light/dark chamber was thoroughly cleaned
with 70% ethanol and dried. The rodents were put into the central
of light compartment facing away the passageway to freely explore
the chamber for 5 min. The time spent in the light side and transi-
tions (the number of crossings from the dark to light compartment)
are recorded for 5 min ( 6 ). As the rodents were not subjected to
any stress in light/dark test, their behavior would not be infl uenced
by this test. Light/dark test results can be analyzed by one-way
between-subjects ANOVAs to determine the effects of treatment
and is followed by post hoc test, such as Newman-Keuls and
Tukey's, if signifi cant main effect is obtained. Typically, analysis of
variance is used to analyze the effects of following measures: transi-
tions between light and dark compartment, time in light compart-
ment. The sample result shows that ( 7 ) 1 mg/kg diazepam and
agmatine at dose of 20 mg/kg signifi cantly increased the number
of the light-dark transitions and diazepam signifi cantly increased
the time spending in light compartment. In these tests, agmatine
had a U-shaped dose-response curve, indicating that agmatine had
anxiolytic-like effect in this model ( 7 ).

1.2.2. Methods