Protocols Preliminary Assessments
The following Preliminary Assessments are being done to:
- provide supplemental information that may aid in the interpretation of data in our primary screens
- identify individuals which may have impairments affecting their performance in a primary screen so that
data is interpreted appropriately or the animal is excluded from testing
- identify individuals which may respond or behave differently in a primary screen and whose data should be viewed differently
Body weight will be determined for each individual at least twice during
the course of the screen. Body weight data is most directly relevant
to the neuroendocrine screen. Altered feeding behavior, activity levels,
and weight gain are all associated with altered HPA axis or HPT axis
activity (see Neuroendocrine screen). Together with anxiety measures
such as the elevated plus maze and open field behavior, animals with
aberrant weight gain may be targeted for follow-up assessment of HPA
function. Additionally, animals with either seriously impaired growth
or obesity may be ill -suited for the 4-week running wheel activity
recording for the circadian screen, and such vulnerable individuals
would be precluded from this test. The measure is rapid, quantitative,
easily accomplished in numerous individuals and will not interfere with
other measures being taken.
Elevated plus maze
The elevated plus maze is frequently employed as a complementary
measure to open field behavior. The maze is constructed with two
enclosed arms and two open arms; the time spent in the enclosed rather
than the open arms is used as a measure of anxiety as the open arms are
anxiety-provoking. Elevated plus maze behavior is sensitive to
experiential modification and social isolation effects. It has been
used as a measure for anxiolytic effects of drugs; significant strain
differences have been reported with good agreement with other anxiety
measures and targeted mutants which would be predicted to have
increased anxiety responses (corticotropin-releasing hormone binding
protein deficient) spend significantly less time in the open arms. The
measure is rapid (5 min duration) and amenable to automation, and
although stressful, should not produce lasting alterations in behavior
that would compromise subsequent tests.
Open field behavior
Open field behavior is actually not a single behavior or measure but
a set of measures which are made in an animal's response to a simple,
novel, and potentially anxiogenic environment. Among the factors which
may be reflected in these measures are exploration, activity, anxiety,
fear, and emotionality/reactivity. In mice, strain differences,
some major gene influences, and QTLs have been identified.
Targeted mutants (knockouts) of the 5-HT5A receptor show increased open
field activity. Like elevated plus maze, it is a rapid (typically
3 or 5 min duration) single trial test, amenable to automation, and
should not be expected to have lasting effects on subsequent measures.
Open field activity (OFA) is a measure of exploration and activity level.
However, animals which are very low in OFA may be inhibited due to innate
fearfulness of an open, brightly lit environment. Animals which are
very inactive may also indicate some other defect which would have direct
relevance to primary screen phenotypes involving activity or activity
related measures, such as wheel-running, freezing, and response to psychostimulants.
The proportion of time spent in the periphery as opposed to venturing
into the center of the open field is used as a measure of the animal's
desire to explore as opposed to its aversion to open, brightly lit environment.
As such, this is used as a measure of fear or anxiety (as opposed to
novelty-seeking). Fear or anxiety measures are important for the neuroendocrine
screen as well as for fear conditioning. Novelty-induced activity also
provides an important baseline for comparison of activity induced by
Open field defecation (OFD) is used as a measure of what is termed "emotionality"
or "reactivity". It provides an index based upon an autonomic
response and does not depend on motor activity. Emotional reactivity
will have significance for the neuroendocrine screen as well as for
measures which rely on emotional responses such as fear conditioning.
The Preyer reflex is a distinctive movement of the pinna in response
to a sudden sound. It can be rapidly measured with the use of a
"clickbox" which emits a 90dB 20kHz sound burst. While not
a quantitative sensitivity measure, it can reliably identify profound
impairments and can discriminate mice with mutations producing deafness.
Since auditory cues are a component of the
fear conditioning tests, animals with such severe impairments need to
be identified. It is very rapid and hence amenable to high throughput,
and it should not compromise subsequent tests. Visual cues are also
obviously a component of the fear conditioning tests, but as visual
function is assessed in a separate primary screen, no vision test is