Analysis of the effects on body temperature of intracerebroventricular injection in anaesthetized dogs of gamma-aminobutyric acid

GABAA and GABAB receptor sites involvement in rat thermoregulation

1. Intraperitoneal (i.p.) injection of muscimol (MUS, 2-8 mg kg-1) decreased the core body temperature (BT) of the rats dose-dependently. 2. Intracerebroventricular (i.c.v.) injection of MUS (1 microgram/microliter/rat) also caused a fall in BT. 3. The hypothermia induced by MUS was inhibited by pretreatment of the animals with either bicuculline (BIC) or picrotoxin (PIC). 4. i.p. Injection of baclofen (BAC, 2.5-10 mg kg-1) induced hypothermia. Higher dose of the drug (20 mg kg-1) caused an initial fall followed by a marked increase in BT. 5. i.c.v. Injection of BAC produced a rise in BT. 6. The hypothermic effect of BAC was antagonized in animals pretreated with either BIC or PIC, while hyperthermic effect of the drug was potentiated with PIC pretreatment. 7. i.c.v. Injection of isoguvacine (ISO) induced hypothermia, which was attenuated in rats pretreated with either BIC or PIC. 8. It can be concluded that: activation of GABAA or GABAB receptor sites respectively may induce hypothermia or hyperthermia in rats.

Effect of pyrimidine nucleosides on body temperatures of man and rabbit in relation to pharmacokinetic data

The effect of high-dose uridine on body temperatures of rabbits and man has been studied in relation to plasma concentrations of uridine and its catabolite uracil. Uridine induced fever in both rabbits and man. High-dose cytidine had no influence on body temperature in rabbits. Plasma concentrations of uridine were between 1 and 1.5 mM at 30 min after an iv bolus injection of 400 mg uridine/kg in rabbits and reached peak levels of 2 mM after a 1-hr infusion of 12 g uridine/m2 in man. The plasma concentration of cytidine in rabbits was about 0.5 mM and that of uridine was 0.30 mM at 30 min after an iv bolus injection of 400 mg cytidine/kg. The mean residence time for uridine in patients and rabbits varied between 80 and 195 min. The area under the plasma concentration-time curve (AUC) for uridine in rabbits was 2.0 mmol.hr/liter, and that for cytidine was 0.6 mmol.hr/liter. A large AUC for uridine indicates a prolonged exposure of tissues to uridine, which might lead to extensive formation of degradation products. The administration of some of these catabolites, dihydrouracil (at 20-40 mg/kg), carbamyl-beta-alanine (at 60 mg/kg), and beta-alanine (at 300-400 mg/kg), resulted in a significant increase in body temperature. It is concluded that the change in body temperature associated with uridine administration was not due to bacterial pyrogens but that one of the degradation products might be involved in thermoregulation.

Effects of GABA natriuresis induced centrally by cholinergic stimulation

Sodium and potassium excretion and urine output have been studied in rats following water loading and intracerebroventricular (i.c.v.) injection of isotonic saline (NaCl-0.15M), gamma-amino butyric acid (GABA), picrotoxin, carbachol, GABA plus picrotoxin, GABA plus carbachol and GABA plus atropine. GABA injection decreased sodium and potassium excretion. Picrotoxin or carbachol injection elicited natriuresis and kaliuresis. GABA injection decreased the effects of the carbachol and atropine injection decreased the effects of the GABA on sodium and potassium excretion. These results suggest an interaction between gabaergic and cholinergic pathways in the control of sodium and potassium excretion.

Effects of delta-aminolaevulinic acid on contractile activity in the isolated small intestine of the rabbit. Role of adrenergic receptors

The porphyrin precursor, delta-aminolaevulinic acid (ALA) at concentrations of 0.23-7.6 mM caused dose-dependent inhibition of spontaneous contractions in isolated preparations of rabbit small intestine, suspended in Ringer-Locke solution. Contractions which returned after inhibition from 3.8 and 7.6mM ALA showed increased amplitude and from 7.6 mM ALA a reduction in rate. Pretreatment with prazosin (10(-7) M) significantly reduced the duration of inhibition exerted by 3.8 and 7.6 mM ALA and also the amplitude of contractions returning after this inhibition. Pretreatment with yohimbine (10(-6) M) and propranolol (7 X 10(-6) M) had no significant effects. Blocking of the release of noradrenaline in preparations by incubation with 6-hydroxydopamine (10(-3) M) or guanethidine (1.5 X 10(-5) M) did not prevent the inhibitory effects of ALA. The alpha 1 agonist, cirazoline (10(-5) M), inhibited contractile activity. This effect was blocked by prazosin (10(-7) M). The alpha 2 agonist, guanoxabenz (10(-5) M) had no detectable effect, in the presence of prazosin, to block any residual alpha 1 actions. It is concluded that alpha 1 receptors mediate inhibitory effects in this preparation and that ALA appears to have direct effects upon these receptors.

Involvement of bicuculline-insensitive receptors in the hypothermic effect of GABA and its agonists

GABA, delta-aminovaleric acid (DAVA) and sodium valproate (VPA) decrease core temperature in conscious rats. Bicuculline increases GABA-induced hypothermia, does not modify DAVA (250 mg/kg) and VPA (100 and 400 mg/kg) hypothermia and antagonizes initial hypothermia by DAVA (1000 mg/kg) and VPA (200 mg/kg) and late hypothermia by DAVA (500 mg/kg) and VPA (200 mg/kg). Picrotoxin increases late hypothermia by GABA (250 mg/kg) and VPA (400 mg/kg), but decreases initial hypothermia by VPA (200 mg/kg). Pentylenetetrazol increases variably GABA-induced hypothermia, inhibits early early hypothermia by DAVA and increases hypothermia induced by VPA (400 mg/kg). We conclude that GABA and GABA-agonists (DAVA and VPA) may induce hypothermia partly mediated by activation of bicuculline-insensitive GABA-receptors.

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.

Changes in body temperature after administration of acetylcholine, histamine, morphine, prostaglandins and related agents

This survey, the second in a series, presents extensive tabulations of literature, primarily since 1965, on thermoregulatory effects of cholinergic agonists and antagonists, histamine and H1- and H2-receptor antagonists, narcotic analgesics and antagonists in both non-tolerant and tolerant subjects and of prostaglandins and related agents. 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.

Changes in body temperature after administration of amino acids, peptides, dopamine, neuroleptics and related agents

Drugs may alter body temperature by acting on any component of the thermoregulatory system. These components include heat production, heat conservation and heat loss effectors and their efferent pathways, thermosensors and their afferent pathways and neurons within the central nervous system that coordinate thermoregulatory effector activities. A thermostat is often thought to be involved although thermoregulation can be explained by models that do not incorporate a thermostat. An action on a particular component can be assessed by determining the effect of a drug on body temperature over a range of environmental temperatures and by observation and measurement of associated changes in effector activities. A scheme for such assessment is presented along with examples of its use. The study of drug-induced changes in body temperature has expanded greatly within the past decade. The primary purpose of this review is to provide a readily available source of information on interactions between certain drugs and the thermoregulatory system. Extensive tables are presented of body temperature changes after administration of amino acids, peptides, dopamine and related agents, phenothiazine neuroleptics and also phenothiazines that lack neuroleptic activity, butyrophenones, diphenylbutylpiperidines such as pimozide and miscellaneous neuroleptics. The information tabulated includes the species used, route of administration and dose of drugs, 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. Most of the cited literature was published since 1965.

Effect of GABA-transminase inhibition on rectal temperature in mice

gamma-Acetylenic GABA (amino-4-hex-5-ynoic acid) and gamma-vinyl GABA (amino-4-hex-5-enoic acid), two catalytic irreversible inhibitors of GABA-transaminase, produce marked sustained elevations in brain GABA concentrations. Associated with these biochemical changes is a decrease in the rectal temperature of mice. This hypothermia can be reversed by increasing ambient temperature. The results suggest GABA plays an important role in mammalian central thermoregulation.

Effects on rectal temperature in rats of gamma-aminobutyric acid; possible mediation through putative transmitters

The rectal temperature of male rats was measured in a thermoneutral environment (25 degrees C) and at ambient temperatures of 15 and 35 degrees C. Unless otherwise specified all drugs were administered intracerebroventricularly (i.c.v.) and all results are reported for the thermoneutral environment. Exposure to 15 degrees C did not affect the rectal temperature but exposure to 35 degrees C produced hyperthermia. At 15 and 25 degrees C, 20 mug GABA produced hyperthermia which was longer lasting at the former ambient temperature. GABA (20 mug) prevented the hyperthermic effect of exposure to 35 degrees C and produced hypothermia in animals maintained at this temperature for 1 hr. A low dose (1 mug) of NA produced hyperthermia and a higher dose (mug) hypothermia. In rats pretreated with sodium salicylate (i.p.), 20 mug GABA and 1 mug NA produced hypothermia instead of hyperthermia, suggesting the release of PGE in mediating hyperthermia. The hypothermic effect of 10 mug NA and of GABA observed at 35 degrees C was blocked by phentolamine, an indication of the possibility of alpha-adrenoceptor mediation.

The antipyretic effect of indomethacin

1. Several possible mechanisms of the antipyretic action of indomethacin administered cat. 2. Indomethacin did not decrease bacterial endotoxin-induced release of endogenous pyrogen in vivo. 3. Indomethacin (5-40 mug/kg) inhibited the pyrogenic effect of peripherally or centrally administered leucocytic progen. A dose of 10 mug/kg caused a parallel shift to the right of the log dose-response curve for I.V. leucocytic pyrogen and reduced the potency of the pyrogen at least 50%. 4. Incubation of leucocytic pyrogen with indomethacin did not alter its pyrogenic potency. 5. Indomethacin exerted only a slight non-dose-related hypothermic effect in afebrile animals. 6. Indomethacin (up to 1 mg/kg) did not diminish the hyperthermic response to intraventricular administration of prostaglandin E1. 7. This pattern of activity indicates that indomethacin acts centrally to inhibit an effect of leucocytic pyrogen.

Effect on body temperature in dogs of perfusion of cerebral ventricles with artificiaL CSF deficient in calcium or containing excess of sodium or calcium

In anaesthetized dogs at room temperatures of 28-33 degrees C, the cerebral ventricles were perfused with artificial CSF from the left lateral ventricular to the aqueductal cannulae. The animals' temperatures were recorded from the rectum. Addition of Ca(++) in excess to the artificial CSF perfusing the ventricles produced hyperthermia and addition of Na+ in excess produced hypothermia. Perfusion with medium deficient in Ca(++) and containing sodium edetate produced hypothermia. The temperature effects of Na(+) or Ca(++) in excess were mutually antagonistic.