The effects of convulsant and anticonvulsant treatments on the behavioural effects of ultrasound presentation in Lister hooded rats.

Lister hooded rats exhibit bursts of locomotion when exposed to a 20 kHz acoustic stimulus; this ultrasound-induced locomotion has been suggested as a potential model for panic attacks. The present studies determined the effects of treatment with the convulsant agents strychnine and pentylenetetrazole and the anticonvulsant agents pentobarbital and ethosuximide on locomotor behaviour elicited by experimenter-presented ultrasounds in Lister hooded rats. Behaviour in a circular arena was viewed live and tracked electronically. In Experiment 1, brief exposure to an ultrasound stimulus typically resulted in short intensity-related bursts of locomotion in control rats. Pentobarbital or ethosuximide treatment reduced this short-term ultrasound-induced locomotion in a dose-related manner, whereas pentylenetetrazole or strychnine treatment increased these locomotor bursts. In Experiment 2, exposure to the ultrasound stimulus for a longer period resulted in irregular cycles of bursts of locomotion followed by periods of relative inactivity in control rats. In addition, approximately 10% of control rats exhibited convulsions associated with this long-duration ultrasound exposure at 98 dB sound pressure level. Sub-convulsant doses of the convulsant treatments increased the frequency of occurrence of convulsions associated with the ultrasound stimulus; pentobarbital or ethosuximide pretreatment significantly reduced this effect. The present findings suggest that a relationship exists between ultrasound-induced locomotor bursts and convulsant activity.