Effects of heating and cooling the spinal cord and medulla oblongata on thermoregulation in monkeys

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Abstract
1. In the unanaesthetized monkey (Macaca cyclopis), heating the spinal cord or the medulla oblongata from 38 to 42-43 degrees C produced subcutaneous vasodilatation, respiratory acceleration (frequently interrupted with a period of apnoea in the medullary experiment), bradycardia and hypotension. The animal became drowsy and had a slight decrease of body temperature. Heating the medulla oblongata often induced retching and/or emesis.2. Cooling the spinal cord or medulla oblongata from 38 to 32-33 degrees C produced subcutaneous vasoconstriction, slower respiration, tachycardia and hypertension. The animal became restless and had a slight increase of body temperature. Cooling the spinal cord induced shivering of the four limbs, while cooling the medulla oblongata induced only shivering of the jaws.3. The effects of heating or cooling of the spinal cord or the medulla oblongata were antagonized by simultaneous application of temperature displacement of the opposite nature in the same areas or vice versa.4. The data suggest that some thermosensitive elements possibly responsible for thermoregulation reside in the spinal cord and the medulla oblongata.