Effects of Adrenergic Stimulation and Inhibition on a Conditioned Fear Response

The purpose of this study was to relate different levels of brain catecholamine& with differential emotional responding. Dopa
was used to facilitate synthesis of NE; R-methyldopa and Dibenxyline
were used to inhibit NE synthesis.
Sa were 80 male Holtzman rats, 85 and 55 days old. The testing
apparatus was a runway with a grid floor and plexiglas& sides, with
a water bottle au one end. After deprived Sa were shaped to run
for water, shock was delivered to the second half of the grid floor.
Sa were injected according to pre-assigned group schedules and
replaced in the testing apparatus 5 hours later. The latency to
the first drinking response was used as a measure of the strength
of the emotional response. Effects of the drugs on general activity
and drinking rate were also measured.
Dopa was found to increase the latency significantly over that
of the controls. Dibenzyline and R-methyldopa did not decrease the
latency relative to the controls. However, the potential of these
drugs was indicated. The drugs were also found to effect general
activity and drinking. Results implicate NE as a mediator of
emotional responding.