Respiratory effects of gamma-hydroxybutyric acid in anesthetized rats

Rats lightly anesthetized with halothane were treated with graded intraperitoneal doses of gamma-hydroxybutyric acid (GHBA), a GABA analogue. The drug induced a dose dependent decrease in minute ventilation, mainly due to reduced respiratory frequency. A reduced pH in arterial blood was recorded. GHBA also blunted or abolished the respiratory response to CO2 exposure in a dose-related way. Picrotoxin (0.25, 0.5 or 1.0 mg/kg intravenously), a presumed GABA antagonist did not significantly change the respiratory pattern when given alone but clearly antagonized the GHBA-induced respiratory depression. It is concluded that GABA-ergic mechanisms are involved in central respiratory control.

Evidence that respiratory depression by serotonin agonists may be exerted in the central nervous system

Resting with CO2 stimulated respiration were measured by means of a whole body plethysmograph in rats lightly anesthetized with halothane. The respiratory effects of different doses of the serotonin precursor 5-HTP, and the serotonin agonist 5-methoxy-N,N-dimethyltryptamine were studied as well as the effects of a serotonin antagonist methysergide and p-chlorophenylalanine, an inhibitor of serotonin synthesis. The serotonergic agonists decreased tidal volume and minute volume in a dose dependent manner and produced a respiratory acidosis. The respiratory depressant effect was antagonized by methysergide, and the serotonergic antagonist and synthesis inhibitor alone stimulated respiration. Rats given intraventricular 5-methoxy-N,N-dimethyltryptamine also evidenced a decrease in tidal volume, and this response was greater in animals given 5,7-dihydroxytryptamine. It seems likely that CNS serotonin receptors are involved in the control of both basal and CO2 stimulated respiration.

Treatment of coccidioidomycosis with ketoconazole: clinical and laboratory studies of 18 patients

Ketoconazole was given to 18 patients with coccidioidomycosis. Fourteen had received prior antifungal chemotherapy with amphotericin B, miconazole, or both. Ten patients had pulmonary disease, two had meningitis, and six had extrameningeal disseminated disease. The initial dose of ketoconazole was 200 mg per day; it was later increased to 400 mg per day for some patients. All strains of Coccididioides immitis tested were sensitive to ketoconazole. Approximately 2-4 hr after an oral dose of 200 mg of ketoconazole, levels of the drug in blood peaked at approximately 2 micrograms/ml. Higher concentrations in blood were achieved with a 400-mg dose. Improvement was measured by physical examination, conversion of cultures previously positive for C. immitis to negative, decrease in erythrocyte sedimentation rate by 50%, and decrease in titer of complement fixation antibody by two or more dilutions. One patient died after one week of treatment with ketoconazole and could not be evaluated; two other patients with coccidioidal meningitis could not be evaluated. Six of nine patients with pulmonary disease showed radiographic improvement, and their sputum cultures, which had been positive, became negative. Four of the six patients with disseminated disease improved. There were few adverse reactions to ketoconazole, which can be safely administered for prolonged periods to patients with coccidioidomycosis. These findings suggest that ketoconazole may be effective for treatment of this disease and indicate that trials comparing the efficacy of ketoconazole with that of amphotericin B are warranted.

Effects of hydrocortisone, phenoxybenzamine and propranolol on the blood plasma levels of adrenaline and noradrenaline during hemorrhagic hypotension in the dog

The adrenergic aspects of the mechanism(s) of the vasodilating action of phenoxybenzamine and massive doses of hydrocortisone were studied in anesthetized dogs subjected to controlled hemorrhagic shock. During the predrug hypotension period with decreased cardiac output and heart rate, the plasma adrenaline and noradrenaline levels were both increased. Phenoxybenzamine injected alone augmented the cardiac output and heart rate and reduced the plasma adrenaline without changing the plasma noradrenaline concentration. However, if the adrenergic alpha-receptor blocker was administered in combination with massive doses of hydrocortisone, the degree of vasodilation increased further with a concomitant increase in the concentrations of the two plasma catecholamines. Thus there seems to be no clear-cut relationship between hemodynamic changes and plasma catecholamines. The present findings illustrate the extreme complexity of plasma catecholamine kinetics during hypovolemic shock.

Dopaminergic interaction with the respiratory control system in the rat

Apomorphine given to rats lightly anesthetized with halothane produces a dose dependent increase in respiratory frequency and minute ventilation. Although basal arterial CO2 tensions were not significantly altered by apomorphine, the mechanical response to exogenous CO2 exposure was greatly increased in rats given apomorphine. Haloperidol returned the apomorphine-stimulated respiratory pattern to control values. It is concluded that dopamine neurons may have important interactions with respiratory control.

The adrenergic mechanism of the haemodynamic effects of massive doses of hydrocortisone in controlled haemorrhagic shock in the dog

Haemorrhagic shock was induced in anaesthetized dogs by bleeding them into a blood reservoir system. By adjusting the blood level of the reservoir at a certain distance over the heart level the mean arterial blood pressure was kept at 6.7 kPa (50 mmHg). As has been found earlier, massive doses of hydrocortisone (80-560 mg.kg-1 body weight) caused a dose-dependent decrease in the total peripheral resistance. The degree of vasodilation distinctly increased during concomitant alpha-receptor blockade induced by phenoxybenzamine. The beta-receptor blocking drug propranolol efficiently inhibited the vasodilation caused by hydrocortisone and phenoxybenzamine. The findings fit with the hypothesis that massive doses of hydrocortisone induce an increased stimulation of the adrenergic beta2-receptors of the vascular smooth muscles.

Haemodynamic effects of different corticosteroids in controlled haemorrhagic shock in the dog

The haemodynamic effects of massive doses of hydrocortisone (80-320 mg.kg-1), methylprednisolone (4-32 mg.kg-1), betamethasone (1.6-12.8 mg.kg-1) and aldosterone (0.1-0.8 mg.kg-1) and the interaction with phenoxybenzamine and propranolol have been studied during controlled haemorrhagic shock in the anaesthetized dog. Hydrocortisone was the only steroid which showed any significant vasodilating ability when given alone. The alpha-receptor blocking agent phenoxybenzamine distinctly decreased the total peripheral resistance. The effect of the phenoxybenzamine was increased in combination with hydrocortisone or methylprednisolone, especially if the steroid was given as the first drug. The vasodilation found was efficiently abolished by the beta-receptor blocking agent propranolol. The ability of hydrocortisone or methylprednisolone to potentiate phenoxybenzamine was not shared by betamethasone or aldosterone. Thus, the haemodynamic effect of the steroid does not seem to be correlated to either a glucocorticoid nor a mineralocorticoid effect. It is suggested that the steroid effect studied is related to the ability of hydrocortisone or methylprednisolone to block the extra neuronal amine uptake which decreases the rate of elimination of the sympathetic transmitter from the vicinity of the adrenergic receptor of the vascular smooth muscle.

Haemodynamic effects of massive doses of hydrocortisone and the interaction with phenoxybenzamine in controlled haemorrhagic shock in the dog

Haemorrhagic shock was produced in anaesthetized dogs by bleeding into a blood reservoir system. The blood level of the reservoir was adjusted at a level above the heart, corresponding to a mean arterial blood pressure of 6.7 kPa (50 mm Hg). The dogs were treated with hydrocortisone and the adrenergic alpha-receptor blocking agent phenoxybenzamine during the hypotension period. Hydrocortisone (80-160 mg kg-1) was found to induce vasodilation, which, however, was of a very small magnitude and was of short duration. Phenoxybenzamine given after hydrocortisone caused very pronounced vasodilation. Hydrocortisone (80 mg kg-1) given after phenoxybenzamine also showed a vasodilator activity, which seemed to be greater than that of the same dose of hydrocortisone given alone. Thus, the vasodilator action of hydrocortisone does not seem to be due to an alpha-receptor blockade of the drug. The vasodilator action of phenoxybenzamine given after hydrocortisone was greater than that of even higher doses of the drug given alone. From the present findings and the fact that corticosteroids are known to potentiate the sympathomimetic action of catecholamines, it is suggested that the hydrocortisone-induced potentiation of the vasodilation action of phenoxybenzamine found is related to an increased vascular adrenergic beta-receptor tone.

Effect of lumbar sympathetic blockade and chlorpromazine-induced adrenergic alpha-receptor blockade on skin temperature in peripheral arterial diseases

The post-cooling toe temperature changes after lumbar sympathetic blockade and after intramuscular administration of an adrenergic alpha-receptor blocking substance (chlorpromazine) were studied in 14 patients with impending gangrene because of peripheral arterial insufficiency. The post-cooling temperature rise was similar after sympathetic blockage and chlorpromazine administration and significantly different from the basal toe temperature changes after cooling. It is concluded that administration of an adrenergic alpha-receptor blocking substance is as good as the lumbar sympathetic blockage for evaluation of a remaining sympathetic vasomotor tone in arterial disease patients.