Separating guinea pig pups from their dams and placing them in a novel environment elicits audible distress vocalizations. This maternal separation paradigm is used as a model of anxiety/stress, and is sensitive to the effects of anxiolytics and anti-depressants [1]. Historically, the duration and frequency of vocalizations were recorded manually, using direct observation or tape recordings. We have significantly increased the accuracy and throughput of the maternal separation test by automating the data acquisition and quantification processes.

Automation was achieved using UltraVox, which measures ultrasonic vocalizations. Audible sound capture was achieved using a standard condensing microphone (100-10,000 Hz) suspended 7.5 inches above the test chamber floor. The standard microphone line feed was too weak to register in the Ultravox system. Therefore, the microphone was connected to a small cassette recorder that provided necessary pre-amplification of the signal and recorded each session's data. The UltraVox system gain was set at 8.0 to record sound greater than 65 dB. Brief extraneous noise was eliminated through the minimum duration filter, a time delay control within UltraVox, which was set to record sound with a minimum duration of 60 ms. A secondary output was available for real time listening. Additional filtering could be applied, if needed, by using a graphic equalizer that provided multi-band width filtering from 16 Hz to 32,000 Hz.

We tested the effects of an anxiolytic (alprazolam) on maternal separation-induced distress vocalizations using the automated system. At 14 days of age, pups were administered alprazolam (0.3, 1 and 3 mg/kg) an hour prior to testing. Pups were then placed individually in a cage (10w x 10d x 16h inches) inside a lit (470 lux) sound attenuation chamber. The amount of vocalization was recorded for 30 min. Our results show that alprazolam significantly inhibited vocalization at doses of 1 mg/kg (68%, p < 0.05) and 3 mg/kg (81%, p < 0.01). Studies are ongoing to further characterize the maternal separation assay in guinea pigs.

References

1. Molewijk, H.E.; Hartog, K.; van der Poel, A.M.; Mos, J.; Olivier, B. (1996). Reduction of guinea pig isolation calls by anxiolytic and antidepressant drugs. Psychopharmacology, 128, 31-38.

Paper presented at Measuring Behavior 2002 , 4^th International Conference on Methods and Techniques in Behavioral Research, 27-30 August 2002, Amsterdam, The Netherlands

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