Acoustic startle induced ultrasonic vocalization in the rat: a novel animal model of anxiety?

Ultrasonic vocalization was induced by either high intensity acoustic stimuli or by electric footshock in the rat. High intensity acoustic stimuli elicit a startle response, while electric footshocks provoke an immediate withdrawal of the feet often accompanied by a pain reaction. Flunitrazepam (0.5 mg/kg), diazepam (5 mg/kg), and ipsapirone (5 mg/kg) reduced the vocalization induced by both averse stimuli. Maprotiline (10-25 mg/kg) enhanced the vocalization. FG 7142 (10 mg/kg) had no effect. The acoustic startle-induced vocalization paradigm like the electric footshock-induced vocalization paradigm may provide a simple and reliable tool in the study of anxiety. The advantage of an acoustic pulse as the averse stimulus is discussed.