Date of Award

5-15-2013

Document Type

Thesis

Degree Name

Bachelor of Arts

First Advisor

Niemiec, Andrew

Abstract

The 22-kHz ultrasonic vocalizations (USVs) of adult rats have been implicated in the communication of alarm between conspecifics. Though these USVs, each composed of several discrete sound units (syllables), are uniformly produced in response to a great variety of stressors, they exhibit biological variation in a number of acoustic features. Such features include number of syllables, syllable and inter-syllable duration, and frequency. The playback of USVs containing fewer syllables, and syllables with shorter duration, has recently been implicated in causing higher levels of alarm in receiving rats, indicating that the semiotics of such vocalizations may extend to transferring information about the nature or level of a threat. The current study was undertaken in order to determine what acoustic differences might be present in the USVs of rats experiencing different affective states. The 5-HT1A agonist 8-OH-DPAT (anxiolytic) and 5-HT2C agonist mCPP (anxiogenic) were utilized to alter the affective state of rats exposed to foot shock, and spectrographic features of USVs produced in response to this stressor were analyzed. Peripheral administration of 8-OH-DPAT decreased production of USVs, both in proportion of rats vocalizing and rate of USV production. Trends suggested longer syllable duration, fewer syllables per USV, and increased start frequency of primary syllables produced by 8-OH-DPAT-treated rats. The effects of mCPP were less clear, likely owing to the drug‰Ûªs interactions with several 5-HT receptor subtypes. Though fewer mCPP-treated rats vocalized as compared to control rats, those that did produced calls that were not significantly different in any of the analyzed spectrographic features. Females as compared to males in vehicle and mCPP groups exhibited increased tone frequency of different call parameters; females also vocalized with longer inter-syllable intervals. In considering the literature on fear potentiation, we hypothesize that learning may be critical in the development of semiotically-distinct 22-kHz USVs.

Comments

Includes bibliographical references (p. 51 - 56)

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