1. In unanaesthetized cats
tranylcypromine (1-10 mg/kg) had scarcely any effect on rectal temperature when injected intraperitoneally, yet such
injections prevented the deep and long-lasting fall in rectal temperature which normally occurs when the cat is anaesthetized by intraperitoneal
pentobarbitone sodium or intravenous
chloralose. The anaesthesia itself, however, was not affected. In some of the experiments with
pentobarbitone sodium rectal temperature even rose to
fever level.2. In anaesthetized as well as in unanaesthetized cats
injections of
tranylcypromine (0.1-1 mg) into the cerebral ventricles caused a rise in rectal temperature.3. In rabbits, rectal temperature was scarcely affected when surgical anaesthesia was produced by
intravenous infusions of
pentobarbitone sodium under the same condition in which, in cats, intraperitoneal
pentobarbitone sodium produced a deep and long-lasting fall in temperature, i.e. when no external heat was applied but excessive dissipation of heat was prevented by placing the rabbit on a cotton-wool pad. However, when it was placed on the
metal surface of an
operating table, the anaesthesia was associated with a deep fall in rectal temperature.5. In anaesthetized and unanaesthetized rabbits
tranylcypromine had no effect on rectal temperature when injected intraperitoneally (10 mg/kg) or into the cerebral ventricles (1 mg).5. These results are discussed in relation to the theory that the three monoamines in the hypothalamus,
5-hydroxytryptamine (5-HT),
adrenaline and
noradrenaline, act as central transmitters in temperature regulation.