Ultrasonic vocalization in rats produced by cholinergic stimulation of the brain.

Neurotransmitters involved in production of ultrasounds in rodents have not yet been identified. It is also not known whether brain mechanisms regulating production of ultrasounds and audible sounds are similar or different. The present study provides the first report that intracerebral injection of an acetylcholine agonist, carbachol, in rats induces ultrasonic vocalization. Since the same agent can induce audible vocalization in cats, the finding suggests a possible common neurochemical substrate underlying production of sonic and ultrasonic vocalization in mammals. The data accumulated to date indicate also that these two kinds of vocalization may play a homologous role in animal communication.