Publication Date


Document Type


First Advisor

Lints, Carlton E.

Degree Name

M.A. (Master of Arts)

Legacy Department

Department of Psychology


Conditioned response


In Experiment I rats were conditioned and tested in a conditioned emotional response (CER) paradigm 96 hours after injection of 316 mg/kg of para-chlorophenylalanine (PCA), a serotonin depletor. Suppression of drinking behavior was used as the index of fear conditioned to the complex CS (a light and a tone). The results indicated that PGA-treated animals did not differ significantly from control Ss in emotionality/ reactivity to external stimulation, or sensitivity to electric foot-shock. In Experiment II, two groups of rats were injected with PCA (316 mg/kg, I.P.) and a third group was given a volumetrically equivalent amount of saline. Water consumption was monitored for nine consecutive days. Ninety-six hours after the first injection, one of the drug groups (PCA-HTP) was given 75 mg/kg 5-Hydroxytryptophan, the immediate precursor of serotonin; the other drug group (PCA-V) and the vehicle-control group (V-V) were injected with a volumetrically equivalent amount of saline. A half hour after the second injection, all Ss were tested for flinch-jump thresholds to electric foot-shock. The water consumption data showed that PCA- treated Ss drank significantly more water than the vehicle Ss for three days after PCA treatment and returned to control levels on the fourth day. There were no significant differences among any of the groups in flinch thresholds, but the PCA-HTP group had a significantly higher jump threshold than either the PCA-V or V-V groups. Although the jump threshold for the PCA-V group was lower than the jump threshold for the V-V group, this difference did not reach significance. The data of Experiment I, in contrast to previous reports, show that PCA induced 5-HT depletion does not decrease emotionality or increase reactivity to external stimulation. It is suggested that earlier results may have been a function of the rat's increased motivation for water rather than a function of depressed serotonin levels. The data of Experiment II supported the observation that PCA increases water consumption for three days after injection, but the results failed to show that PCA increases sensitivity to electric foot-shock.


Includes bibliographical references.||Includes illustrations.


58 pages




Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type