Body temperature responses in cats and rabbits to the monoamine oxidase inhibitor tranylcypromine

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC, CNS depressants and stimulants, hormones, inorganic ions, gases, 2,4-DNP and miscellaneous agents

This survey concludes a series of complications of data from the literature, primarily published since 1965, on thermoregulatory effects of antipyretics in afebrile as well as in febrile subjects, LSD and other hallucinogens, cannabinoids, general CNS depressants, CNS stimulants including xanthines, hormones, inorganic ions, gases and fumes, 2,4-dinitrophenol and miscellaneous agents including capsaicin, cardiac glycosides, chemotherapeutic agents, cinchona alkaloids, cyclic nucleotides, cycloheximide, 2-deoxy-D-glucose, dimethylsulfoxide, insecticides, local anesthetics, poly I:poly C, spermidine and spermine, sugars, toxins and transport inhibitors. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary agents.

Changes in body temperature after administration of adrenergic and serotonergic agents and related drugs including antidepressants

This survey, the third in a series, presents extensive tabulations of literature, primarily since 1965, on thermoregulatory effects of adrenergic and serotonergic agonists and their antagonists including ergot alkaloids, amphetamines, tryptamines, monoamine oxidase inhibitors, tricyclic and other antidepressants, a variety of other agents which alter presynaptic aminergic mechanisms including reserpine, 6-hydroxydopamine, p-chlorophenylalanine, alpha-methyltyrosines, cocaine, guanethidine and bretylium. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions, such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary drug.

Biological bases for the integration of appetitive and consummatory grooming behaviors in the cat: a review

Cats with pontile lesions, frontal neocortical lesions, and thyroidectomized cats display a dissociation of the appetitive and consummatory components of grooming behavior following tactile stimulation of the body surface, an abnormal behavior which waxes and wanes with the seasons of the year. Tryptophan hydroxylase activity and serotonin levels were significantly decreased in the superior colliculi (but not other brain regions) in cats with pontile lesions or frontal neocortical lesions, but not in thyroidectomized cats. Systemic administration of 5-hydroxytryptophan or monoamine oxidase inhibition plus tryptophan administration abolishes the abnormal grooming behavior in each group of cats, and microinjections of 5-hydroxytryptophan or serotonin into the superior colliculi has the same effect, indicating that the change in a serotonergic system is a critical aspect of the abnormal behavior in cats with lesions and that a serotonergic system may also be involved in the genesis of the abnormal grooming behavior in thyroidectomized cats. Functional inactivation of the serotonergic system by p-chlorophenylalanine, LSD, or serotonin receptor blockade does not induce the abnormal grooming behavior in normal cats, indicating that other factors are involved. Cats with lesions and thyroidectomized cats display a rhythmic dysfunction in the excretion of glucocorticoids and glucocorticoid administration abolishes the abnormal grooming behavior, suggesting that glucocorticoids are the other critical factor. Adrenalectomized cats do not display the abnormal grooming behavior, but when adrenalectomized cats are treated with p-chlorophenylalanine, the abnormal behavior appears. Thus, a serotonergic system in the superior colliculi, operating at some level of glucocorticoid function, is involved in the integration of appetitive and consummatory grooming behaviors.

Role of 5-hydroxytryptamine in ketamine-induced hypothermia in the rat

1. Intraperitoneal injection of graded doses of ketamine produced a dose-dependent fall in body temperature of rats. Similarly, intracerebral injection of much smaller doses produced hypothermia.2. Pretreatment of the rats with p-chlorophenylalanine (PCPA) greatly attenuated the hypothermic response to ketamine whereas the intraperitoneal injection of 5-hydroxytryptophan in PCPA-treated rats restored the hypothermic effect of ketamine.3. Depletion of the brain monoamines by reserpine completely prevented the ketamine-induced hypothermia. Treatment with sodium diethyldithiocarbamate (DEDTC), however, did not modify the hypothermic effect of ketamine.4. Pretreatment of the rats with pargyline potentiated the ketamine-induced hypothermia.5. Depletion of brain monoamines by reserpine in combination with inhibition of noradrenaline biosynthesis (DEDTC) resulted in a long lasting fall in temperature which was not modified by ketamine.6. When the ambient temperature was raised from 26 degrees C to 32 degrees C, ketamine-induced hypothermia was much reduced and superimposed on a hyperthermia which occurred in all animals.7. It is concluded that ketamine produces hypothermia in rats possibly through the release of 5-hydroxytryptamine in the hypothalamus and that this effect is similar in some respects to that produced by morphine in non-tolerant rats.

Temperature responses and other effects of 5-hydroxytryptophan and 5-hydroxytryptamine when acting from the liquor space in unanaesthetized rabbits

1. In unanaesthetized rabbits 5-hydroxytryptophan (5-HTP) and 5-hydroxytryptamine (5-HT) were injected into the cisterna magna or into the cannulated left lateral cerebral ventricle while rectal temperature was recorded.2. 5-HTP injected intracisternally in a dose of 1.5-3 mg produced a fall in temperature often followed by a rise beyond the pre-injection level. With 6 mg the main effect was a rise in temperature. The intraventricular injection of 1-2 mg 5-HTP usually produced a fall followed by a rise.3. 5-HT injected intracisternally in a dose of 0.2 mg produced a fall in temperature similar to that produced with this dose injected intraventricularly. Following an intracisternal injection of 1-4 mg 5-HT there was either a fall, or a fall followed by a rise, but in a few experiments the effect consisted mainly of a rise in temperature.4. Additional effects regularly observed with these injections were tachypnoea, ear twitching, rapid movements of the vibrissae, shaking of the head, wiping and scratching movements, ataxia, nodding and sideways movements of the head and long-lasting catalepsy.5. The sites where 5-HTP and 5-HT act when producing the temperature responses and the various behavioural effects are discussed.

Acute effects of a monoamine oxidase inhibitor, tranylcypromine, on thermoregulation in the conscious rabbit

1. The effect of a single injection of the monoamine oxidase inhibitor, tranylcypromine, administered intravenously (20 mg/kg) or into the lateral cerebral ventricle (5-10 mg), on hypothalamic and rectal temperature, has been investigated.2. Intravenous tranylcypromine causes a significant rise in body temperature, which is due, at least in part, to cutaneous vasoconstriction; this vasoconstriction is augmented by sympathectomy. It is concluded that this vasoconstrictor effect is not mediated via the central nervous system.3. Intraventricular tranylcypromine caused a transient but significant fall in core temperature. This is interpreted as being compatible with selective augmentation of hypothalamic levels of 5-hydroxytryptamine.

Effects of monoamine oxidase inhibitors and amphetamine on hypothermia produced by halothane

1. In cats, the effects of tranylcypromine and pheniprazine, two monoamine oxidase (MAO) inhibitors with strong amphetamine-like actions, of pargyline, an inhibitor without amphetamine-like actions, and of amphetamine itself, were examined on the hypothermia produced by a 2 hr period of halothane inhalation.2. The hypothermia was prevented by intraperitoneal injections of the three MAO inhibitors. Tranylcypromine and pheniprazine acted in doses of a few milligrams, pargyline in doses of over 100 mg.3. The hypothermia was prevented by injections into the cerebral ventricles of tranylcypromine and pheniprazine, in doses which were effective also on intraperitoneal injection; intraperitoneal injections were sometimes more effective. The large doses of pargyline needed to prevent the hypothermia when injected intraperitoneally were not tested by the intraventricular route, as the injections had to be made in a volume of 0.1 ml. In smaller doses intraventricular pargyline was not effective.4. The hypothermia was prevented by an intraperitoneal or intraventricular injection of amphetamine in a dose as little as 1 mg; intraperitoneal injections were sometimes more effective.5. The effects of tranylcypromine and pargyline given intraperitoneally, and of amphetamine given intraventricularly as well, were also examined on the hypothermia produced by an intraventricular injection of 200 mug noradrenaline. The two MAO inhibitors and amphetamine prevented the hypothermia, or greatly reduced it.6. It is concluded (a) that even on intraventricular injection the MAO inhibitors must first be absorbed into the blood stream before they can prevent the hypothermia of a halothane anaesthesia; (b) that their action may not be solely on the anterior hypothalamus; and (c) that they may not act only through MAO inhibition.

Effects of monoamine oxidase inhibitors on the hypothermia produced in cats by halothane

1. In cats, the effects of intraperitoneal injections of four monoamine oxidase (MAO) inhibitors, tranylcypromine, pheniprazine, pargyline, and nialamide, were examined on rectal temperature and on the hypothermia during anaesthesia produced by a 2 hr period of halothane inhalation.2. A 2 hr period of halothane inhalation produced a steady fall in temperature amounting to between 2 degrees and 3.5 degrees C. After discontinuation of halothane inhalation, temperature quickly returned to the pre-anaesthetic level but no pyrexia developed. A peculiar stiffness of the leg muscles occurred in several experiments either at the beginning of the inhalation or after its discontinuation.3. An injection of tranylcypromine (5 mg/kg) caused a rise in rectal temperature and prevented the hypothermia of halothane anaesthesia. This effect lasted for at least 4 hr; 20 hr after the injection, halothane again caused hypothermia.4. An injection of pheniprazine (10 mg/kg) usually caused a small rise in temperature which was not sustained. Pheniprazine not only prevented the hypothermia of halothane anaesthesia during the subsequent 20 hr, but during the first few hours after the injection halothane inhalation actually produced a steep rise in temperature.5. An injection of pargyline (50 mg/kg) had no effect on temperature but the hypothermia due to halothane inhalation was prevented 1 hr after the injection and attenuated after 20 hr. Injection of 200 mg/kg caused a steady rise in temperature which was accelerated when halothane was administered 1 hr later.6. An injection of nialamide (10, 25 or 50 mg/kg) had no immediate effect on temperature, but pyrexia developed overnight after the two larger doses. The effect on the hypothermia due to halothane inhalation was greater 20 hr after the injection than it was after 1 to 2 hr. Twenty hours after injection of the two larger doses, halothane no longer produced hypothermia but caused a lethal rise in temperature either during or after its inhalation.7. In rabbits, the effect on temperature of halothane inhalation varied. Either temperature rose slightly or it fell, but not as much as in cats. In one rabbit in which the inhalation had produced a transient rise, pyrexia developed 40 min after discontinuation of halothane.

Central temperature regulation in the conscious rabbit after monoamine oxidase inhibition

1. Measured thermal loads were applied to conscious rabbits by intravenous infusions of hot or cold saline. The responses of the central temperature regulating mechanism were assessed by measuring hypothalamic temperature change. The relationship between thermal load and temperature response was established in normal animals.2. Intramuscular injection of tranylcypromine (20 mg/kg. day for 6-8 days) had no effect upon resting temperature or the temperature response to thermal loads, though the diencephalic concentrations of noradrenaline and 5-hydroxytryptamine (5-HT) were increased.3. Either hypothalamic monoamines are not concerned in the regulation of normal temperature or there is a monoamine ;pool' in the hypothalamus which is concerned with temperature regulation but which is unaffected by monoamine oxidase inhibition.

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

1. In dogs the effects on rectal temperature of noradrenaline, adrenaline, 5-hydroxytryptamine (5-HT) and of the monoamine oxidase inhibitor tranylcypromine were studied following their injection into the third ventricle through a chronically implanted cannula. Tranylcypromine was given also by the intraperitoneal route.2. The hypothermic effect of the catecholamines and the hyperthermic effect of 5-HT previously demonstrated in anaesthetized dogs were obtained also in an unanaesthetized dog, but 5-HT was effective only in doses under 20 mug.3. Tranylcypromine (1 mg) injected into the third ventricle of dogs anaesthetized with pentobarbitone sodium produced shivering and a rise in temperature.4. Tranylcypromine (10 mg/kg) injected intraperitoneally caused a rise in temperature in the unanaesthetized dog. For a time shivering and panting, two effects which produce opposite change in temperature, were observed together. When injected shortly before an intraperitoneal injection of an anaesthetizing dose of pentobarbitone sodium, tranylcypromine not only prevented the fall in temperature which is normally produced by the anaesthetic but caused a greater and longer lasting rise than when given alone.5. 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.6. In rhesus monkeys anaesthetized with intraperitoneal pentobarbitone sodium, noradrenaline, adrenaline, 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.