Characterization of ultrasonic hearing thresholds and vocalizations in the Dbh-mutant backcrossed CBA/CaJ mouse Open Access

Wong, Gerald Junwei (2015)

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Vocal communication is an essential natural behavior that might be modulated by neuromodulatory mechanisms, such as the noradrenergic system. In order to study the effects of norepinephrine (NE) on the production of vocal cues and auditory processing, we generated a genetic knockout of NE by backcrossing a nonfunctioning dopamine beta hydroxylase (Dbh) allele from a C57BL/6J and 129/SvEv background onto CBA/CaJ mice. CBA/CaJ mice are known for better high frequency hearing, which allows us to study auditory processes that involve natural, socially relevant ultrasonic vocalizations. In this study, we characterized this genetic knockout in parameters such as hearing thresholds, including at high frequencies, and vocalization production during development. To characterize hearing thresholds we used auditory brainstem response recording and to characterize vocalization production we recorded isolation-induced pup ultrasonic vocalizations. Hearing thresholds and acoustic features of vocalizations produced by Dbh backcrossed mice, both heterozygotes and wild-types, did not differ significantly from the background CBA/CaJ mouse strain, and had significantly better hearing than the Dbh mutant background strain. Within the NE-competent Dbh backcrossed CBA/CaJ mice, we compared the acoustic features of the vocalizations from the Dbh +/+ wild-type mice with Dbh +/- heterozygotes and found no differences in vocalization frequencies, durations, and rate of calling. Hearing was not different in NE-competent CBADbh mutants compared to CBA/CaJ mice. These results indicate that a single mutant Dbh allele does not affect normal vocalization production and hearing. In one Dbh knockout (-/-) mouse, we observed decreased rates of vocalizations, suggesting NE knockout mice might have abnormal vocal production.

Table of Contents

Introduction. 1

Materials and Methods. 5

Results. 14

Discussion. 20

Figure 1. 26

Figure 2. 27

Figure 3. 28

Figure 4. 29

Figure 5. 30

Figure 6. 31

Figure 7. 32

Figure 8. 33

Table 1. 34

Figure 9. 35

Figure 10. 36

References. 37

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