Patterns of cardiovascular and respiratory responses evoked by stimulation of the defense area in the white-belly opossum (Didelphis albiventris)

The present study describes, for the first time, the autonomic changes concomitant to the defense reaction in the opossum. Electrical stimulation of 2305 sites in the hypothalamus and brain stem evoked from 7% of them patterns of response including 40-240% muscle vasodilatation, characteristic of the defense reaction in anaesthetized animals. These responses also included a rise in arterial blood pressure, tachy- or bradycardia, and variable changes in ventilation ranging from apneusis to polypnea. It is suggested that the defense areas of the opossum are similar to those described for other species, but the defense responses resemble those of the rabbit