Reflex chemoceptive excitation of diencephalic sham rage behavior

In acute thalamic cats, excitation of the carotid body chemoceptors was induced by intrasinusal injection of lobeline (10 µg) or by administering low oxygen mixtures (5–12% O 2 in N 2 ). Bilateral section of the cervical vago-aortic trunks, preliminary to the experiment, permitted the exclusion of the aortic chemoceptive areas from our study. Stimulation of the carotid body chemoceptors was constantly capable of evoking sham rage outbursts identical in pattern and intensity to those induced by tactile or noxious stimulation or occurring spontaneously. When low-intensity stimulation was used (10–12% O 2 ) the rage fits were preceded in time by signs of excitation of the medullary respiratory and vasomotor centers. Since lobeline and hypoxia became unable to evoke sham rage outbursts following selective inactivation of the carotid body chemoceptors it is concluded that the diencephalic mechanisms for rage behavior are within the sphere of influence of chemoceptive reflexes.