Haemophilus influenzae induces a potentiated increase in guinea-pig pulmonary resistance to histamine

The human respiratory pathogen Haemophilus influenzae (H.i.) induced bronchial hyperreactivity to histamine (1.0–8.0 μg/100 g b.w. i.v.) in vivo in anaesthetized spontaneously breathing guinea-pigs. This hyperreactivity was caused by a potentiated increase in pulmonary resistance. Decreases in dynamic compliance did not differ. Atropine prevented the potentiation at 1.0 and 2.0 μg histamine/100 g b.w. These results show that H.i. induces bronchial hyperreactivity in vivo which is mediated by direct and reflex effects of histamine in the central airways

α-Methylnoradrenaline induced hypotension and bradycardia after administration into the area of the nucleus tractus solitarii

Bilateral injections of α-methylnoradrenaline into the area of the nucleus tractus solitarii of the brain stem caused a dose-dependent decrease of systemic arterial blood pressure and heart rate of anesthetized rats. The effects were prevented and even reversed by a preceding injection of the α-adrenoceptor blocking agent phentolamine. Pressor doses of angiotensin II and of arginine-vasopressin at the same site failed to decrease blood pressure and heart rate

Effects of dietary linoleic acid on beta-adrenergic responsiveness of the guinea pig respiratory system

Respiratory autonomic β-adrenergic receptor function was investigated in isolated tracheal spirals of guinea pigs receiving different diets. Comparison was made between control and Haemophilus influenzae treated animals; this latter group serving as animal model for atopy. The different semi-synthetic diets (35 energy%) varying in their linoleic acid contents (5.85, 11.25 and 22.05 en%), exerted profound effects on membrane fatty acid composition. No influence of these diets on either food intake or growth could be detected. Isoprenaline induced relaxation of guinea pig tracheal spirals was maximal in the dietary group receiving moderate linoleic acid (11.25 en%). Both the addition and the withdrawal of linoleic acid to this diet resulted in a significant impariment of β-adrenergic receptor function, to the same extent as can be induced by Haemophilus influenzae. The results are discussed in view of current concepts for atop

Effects of dietary linoleic acid on beta-adrenergic responsiveness of the guinea pig respiratory system

Respiratory autonomic β-adrenergic receptor function was investigated in isolated tracheal spirals of guinea pigs receiving different diets. Comparison was made between control and Haemophilus influenzae treated animals; this latter group serving as animal model for atopy. The different semi-synthetic diets (35 energy%) varying in their linoleic acid contents (5.85, 11.25 and 22.05 en%), exerted profound effects on membrane fatty acid composition. No influence of these diets on either food intake or growth could be detected. Isoprenaline induced relaxation of guinea pig tracheal spirals was maximal in the dietary group receiving moderate linoleic acid (11.25 en%). Both the addition and the withdrawal of linoleic acid to this diet resulted in a significant impariment of β-adrenergic receptor function, to the same extent as can be induced by Haemophilus influenzae. The results are discussed in view of current concepts for atop

Central inhibitory effect of α-methyldopa on blood pressure, heart rate and body temperature of renal hypertensive rats

The central inhibitory effect of α-methyldopa on blood pressure, heart rate and body temperature was studied in conscious renal hypertensive rats. Systemic administration of α-methyldopa decreased mean arterial blood pressure and body temperature and caused a short lasting increase in heart rate followed by a long lasting decrease. Inhibition of central decarboxylase activity prevented the decrease in blood pressure, heart rate and body temperature but not the initial increase in heart rate. Inhibition of peripheral decarboxylase activity blocked the increase in heart rate and partially reduced the decrease in heart rate and body temperature but did not affect the decrease in blood pressure. α-Methyldopa also decreased blood pressure at an ambient temperature of 30°C, but the decrease of body temperature was absent and the heart rate remained elevated for 7 hr. Similar results were obtained in normotensive rats. The decrease in heart rate was correlated with the decrease in body temperature in normotensive and renal hypertensive rats. These findings suggest that in the renal hypertensive rat the decrease in blood pressure and in body temperature depends on a central action of α-methyldopa metabolite