Testosterone modulates stimulation-induced calling behavior in Japanese quails

Japanese quails have a variety of calling patterns depending on sex and age. Sexually mature adult males emit a characteristic crow which has a frequency-modulated acoustical trill element. Recently we reported that the intercollicular nucleus of the mesencephalon is the vocal neural system for producing the distress call in untreated chick and the crowing vocalization in testosterone-treated chick in Japanese quails. We postulated that the intercollicular nucleus could mediate this testosterone action on vocal behavior. The present study showed histologically that the intercollicular nucleus neurons of adult males have many more dendrites than those of females. The adult males produced the call with trill element with electrical stimulation of the intercollicular nucleus alone. Females produced the simple call, which has no frequency modulation, with electrical stimulation; 4 days after the testosterone treatment together with electrical stimulation, they also produced the call with trill element, the characteristic call of males. We suggest that the vocal neural system in the intercollicular nucleus is modulated by testosterone during development and produces the crow in males, and the intercollicular nucleus neurons in adults mediate the action of testosterone on vocal behavior. The crow of adult males could therefore be due to effects of testosterone on the neural mechanism in the intercollicular nucleus.