Temperature effects produced in dogs and monkeys by injections of monoamines and related substances into the third ventricle

Abstract

In dogs the effects on rectal temperature of noradrenaline [norepinephrine], adrenaline [epinephrine], 5-hydroxytryptamine (5-HT) and of the monoamine oxidase inhibitor tranylcypromine were studied following their injection into the 3rd ventricle through a chronically implanted cannula. Tranylcypromine was given also by the intraperitoneal route. The hypothermic effect of the catecholamines and the hyperthermic effect of 5-HT previously demonstrated in anesthetized dogs were obtained also in an unanesthetized dog, but 5-HT was effective only in doses under 20 [mu]g. Tranylcypromine (1 mg) injected into the 3rd ventricle of dogs anesthetized with pentobarbitone sodium produced shivering and a rise in temperature. Tranylcypromine (10 mg/kg) injected intraperitoneally caused a rise in temperature in the unanesthetized dog. For a time shivering and panting, 2 effects which produce opposite change in temperature, were observed together. When injected shortly before an intraperitoneal injection of an anesthetizing dose of pentobarbitone sodium, tranylcypromine not only prevented the fall in temperature which is normally produced by the anesthetic but caused a greater and longer lasting rise than when given alone. The intraperitoneal injections of tranylcypromine produced profuse salivation, a peripheral effect which persisted after acute denervation and which was not abolished by atropine or tolazoline. In rhesus monkeys anesthetized with intraperitoneal pentobarbitone sodium, noradrenaline [norepinephrine], adrenaline [epinephrine], 5-HT and 5-hydroxytryptophan (5-HTP) were injected into the cannulated third ventricle. The catecholamines caused a fall in rectal temperature. No evidence was obtained that the fall resulted from a rise in hypothalamic temperature. The injections of 5-HT or of its precursor 5-HTP raised rectal temperature. Monkeys thus respond to the monoamines injected intraventricularly, in the same way as cats and dogs, and unlike rabbits, sheep, goats, oxen and rats.