Emotional and Anxiety Assessments in CNS Disorders - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 248

at 0.5 mg/kg signifi cantly increased social interaction compared
with the vehicle-treated subjects, suggesting that these two com-
pounds at specifi c dose have anxiolytic effects ( 11 ). It also should
be noticed that the locomotor activity is not altered by these two
compounds.

Sex difference existed in that female rodents do not increase social
interaction as remarkably as male counterparts in familiar test
area ( 12 ). Environmental factors have been shown to alter social
interaction. Rats housed in noisy room for 24 days showed robustly
lower level of social interaction than those housed in quite condi-
tion ( 13 ). Rats exposed to odor of cat or fresh rat blood for 5 min
showed signifi cant anxiogenic effects when tested in social interac-
tion test. Aggressive behavior occasionally occurs. This will lead
to freezing or avoidance of other subject. The score of this pair
should be discarded.

1.3.3. Notes

This test utilizes behavioral changes in rodents exposed to a novel
environment and has been used to evaluate anxiogenic and anxi-
olytic activities. The naive mouse is placed at one corner of the
chamber and allowed to explore for 5 min. The latency (the time
taken to move from the corner square to the next adjacent square),
exploration (the number of squares crossed), and rears (the number
of times the animals stood on their rear paws) are recorded ( 6 ).

1.4. Open Field Test

The fl oor of the open-fi eld chamber (50 × 50 × 25 cm), which is
made of white plexiglass, is divided into 16 identical squares by
visible lines on the fl oor. The lines divided the fl oor into sixteen
12.5 × 12.5-cm squares. Some laboratories draw a central square in
the middle of the open fi eld because some strains of rodents have
high locomotor activity and cross the lines of the test box many
times during a test session. The central square gives an easier way
to distinguish central location from the outer locations. A video
camcorder mounted on the top of the box is used to record for
subsequent analysis.

1.4.1. Materials
and Equipment

The animals are transferred to test room with transfer cages 1 h
prior to the test. The apparatus is thoroughly cleaned with 70%
EtOH and allowed to dry between tests. The naive animal is placed
at one corner of the chamber and allowed to freely explore for
5 min. The latency to exploration and rears are recorded. A sample
result showed that PDE4B−/− mice increased in the latency to exit
the initial quadrant and decreased in initial exploration and rears.
These data suggest that mice defi cient in PDE4B display anxiogenic-
like behavior. These effects appeared not to be associated with
changes in general activity since PDE4B−/− mice did not show
altered locomotor activity ( 6 ).

1.4.2. Methods