Brudzynski_1988_Neuropsychopharmacology_1_311

Vocalization induced by injections of carbachol into the anterior hypothalamic/preoptic area is regarded as an index of emotional behavior and offers a useful measure of emotional expression. Reproducibility and dose-dependence of the carbachol-induced vocalization, however, have not previously been systematically studied. The present study showed that the magnitude of vocalization was dose-dependent within the range of eight doses and increased in a 20-fold range from 0.5 to 10.0 micrograms, reaching its maximal plateau between 10.0 and 20.0 micrograms. Higher doses (20.0 to 80.0 micrograms) caused a decline of the vocalization. In contrast, the magnitude of vocalization was reproducible for eight injections of the same dose (10.0 micrograms). The carbachol-induced responses were decreased by repeated injections of high dosage or large volume of carbachol solution, and were reversed by atropine. The present results support the suggestion that carbachol-induced vocalization may serve as a measurable model for studying emotional behavior.