Abstract: In order to investigate the vocalization mechanism of the "groa- ning center" in cats, we studied the effect of microinjection of glu- tamate and kainic acid into the "groaning center"on groaning respon- ses. It was found that the respiratory rate increased markedly and the pupils of cats dilated immediately after injection. Furthermore, the threshold of groaning responses induced by electrical stimulation reduced significantly after injection. In some cats, it was also obser- ved that groaning responses could be directly induced by kainic acid. Our results suggested that the vocalization elicited by electrical stimulation of the "groaning center" represent responses due to the activation of neuronal cell bodies.

Key words: glutamate, kainic acid, groaning center, groaning response, cat