Snoeren Eelke M S, Ågmo Anders
Department of Psychology, University of Tromsø
J Comp Psychol. 2014 Feb;128(1):40-55. doi: 10.1037/a0033204. Epub 2013 Sep 16.
Rats emit ultrasonic vocalizations (USVs) of 22 kHz and 50 kHz before, during, and after copulation. The 50-kHz vocalizations can be subdivided into flat and frequency-modulated (FM) trill calls. In this study, the role of 50-kHz USVs in sexual incentive motivation in female rats was examined. USVs were recorded from sexually active males during the precopulatory phase. In the first two experiments, "full 10-min song," flat-call, and FM-trill-call stimuli were used. In Experiment 1, a combination of complex and trill calls was used as the FM-trill call, whereas a mixture of multistep and upward ramp calls was used in Experiment 2. The auditory stimuli were played back to sexually receptive female rats in a sexual incentive-motivation test. For comparison, the odor of an intact male rat was also used as incentive stimulus. The flat-call stimulus did not induce approach behavior in any experiment, whereas the FM trill showed a short-lived effect in Experiment 2. The females approached the "full song" during the first minute of stimulus exposure in Experiment 1, but not in Experiment 2. When the entire 10-min test period was analyzed, the females in Experiment 1 did not approach the full song more than background noise, though they did so in Experiment 2. The olfactory stimulus, to the contrary, had a clear incentive value in both experiments. In a third experiment, a devocalized male, an intact vocalizing male and a female rat were used as incentive stimuli. The females did not approach a vocalizing male more than they approached a silent male, showing that USVs do not contribute to the male rat's incentive value. Overall, the results of the present series of experiments show that the male rat's USVs do not have any consistent incentive value for the sexually receptive female rat. This sharply contrasts the strong and reliable effect of male odor.
大鼠在交配前、交配期间和交配后会发出22千赫兹和50千赫兹的超声波发声（USV）。50千赫兹的发声可细分为平稳型和调频（FM）颤音叫声。在本研究中，研究了50千赫兹USV在雌性大鼠性动机激励中的作用。在交配前期从性活跃的雄性大鼠中记录USV。在前两个实验中，使用了“完整的10分钟歌声”、平稳型叫声和FM颤音叫声刺激。在实验1中，将复杂叫声和颤音叫声的组合用作FM颤音叫声，而在实验2中使用了多步叫声和向上斜坡叫声的混合。在性动机激励测试中，将听觉刺激回放给性接受期的雌性大鼠。为了进行比较，完整雄性大鼠的气味也用作激励刺激。在任何实验中，平稳型叫声刺激都不会诱发接近行为，而FM颤音在实验2中显示出短暂的效果。在实验1中，雌性大鼠在刺激暴露的第一分钟内接近“完整歌声”，但在实验2中没有。当分析整个10分钟的测试期时，实验1中的雌性大鼠接近完整歌声的程度并不比背景噪音更多，尽管它们在实验2中是这样做的。相反，嗅觉刺激在两个实验中都具有明显的激励价值。在第三个实验中，使用了去声雄性大鼠、完整发声的雄性大鼠和雌性大鼠作为激励刺激。雌性大鼠接近发声雄性大鼠的程度并不比接近沉默雄性大鼠的程度更高，这表明USV对雄性大鼠的激励价值没有贡献。总体而言，本系列实验的结果表明，雄性大鼠的USV对性接受期的雌性大鼠没有任何一致的激励价值。这与雄性气味的强烈且可靠的效果形成了鲜明对比。
