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Reduction of cardiovascular responses to some sympathomimetic amines during hypercapnia
Ist Teil von
European journal of pharmacology, 1972-05, Vol.18 (2), p.166-173
Ort / Verlag
Netherlands: Elsevier B.V
Erscheinungsjahr
1972
Link zum Volltext
Quelle
Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
Beschreibungen/Notizen
The cardiovascular effects of noradrenaline, adrenaline, isoprenaline and orciprenaline were examined in rats before, during and after a period of hypercapnia produced by ventilation with 10% CO
2 in air. This procedure increased the
PCO
2 from 37 to 79 mm Hg and was accompanied by an acidosis with a fall in pH from 7.39 to 7.08. The increases in heart rate in response to adrenaline, isoprenaline and orciprenaline were abolished or reduced during hypercapnia. The pressor responses to noradrenaline and adrenaline, and the depressor responses to isoprenaline and orciprenaline were also reduced. The changes in responses to these amines produced by hypercapnia were rapid in onset, and were restored towards control levels when the animals were returned to ventillation with air. These effects were not due to desensitization of receptors by catecholamines released from the adrenals, since in adrenalectomized rats hypercapnia produced the same changes in responses to noradrenaline and isoprenaline as in intact rats. They may have been due to desensitization of receptors by catecholamines released from sympathetic nerves, by the depressant effect of a high level of CO
2, or to changes in receptor configuration with the fall in pH. The findings do not suggest any increased hazard of sympathomimetic bronchodilators in severe asthma with hypercapnia.