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Cardiorespiratory effects induced by acetazolamide on the ventromedullary surface of the cat.
Author(s) -
Andreattavan Leyen S,
Averill D B,
Guertzenstein P G
Publication year - 1990
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1990.sp017939
Subject(s) - acetazolamide , chemistry , chemoreceptor , baroreceptor , anesthesia , heart rate , central chemoreceptors , cats , respiratory system , blood pressure , chloralose , endocrinology , medicine , biochemistry , receptor
1. Inhibition of carbonic anhydrase by acetazolamide in alpha‐chloralose‐anaesthetized cats, in a region of the brain stem co‐extensive with the glycine‐sensitive area, intermediate chemosensitive area, and probably C1 catecholaminergic neurones produces hypotension, bradycardia and depression of the central respiratory drive. 2. These responses are concentration dependent, and can still be observed when the enzyme substrate (CO2) is elevated. Therefore, in both the hypercapnic and the normocapnic condition, similar responses in arterial blood pressure, heart rate and respiratory rate are observed when acetazolamide is topically applied to the glycine‐sensitive area. 3. To investigate further the contribution of peripheral baro‐, chemo‐ and cardiopulmonary receptors to these responses, acetazolamide was topically applied to the glycine‐sensitive area under three different conditions: intact gallamine‐paralysed (5 mg kg‐1 h‐1) and artificially ventilated (A), sinoaortic denervated (B), and sinoaortic denervated plus bilaterally vagotomized cats (C). Under all conditions, similar responses were observed. The fall in arterial blood pressure was 75 +/‐ 11 (A), 90 +/‐ 13 (B), and 75 +/‐ 9 mmHg (C). Changes in heart rate during acetazolamide application were ‐23 +/‐ 6, ‐20 +/‐ 8, and ‐26 +/‐ 6 beats min‐1, respectively. The decreases in respiratory rate were 9 +/‐ 2 (A), 11 +/‐ 2 (B), and 11 +/‐ 2 breaths min‐1 (C). 4. The data indicate that the responses to topical application of acetazolamide are mainly due to its central action at the glycine‐sensitive area and are not influenced by peripheral baroreceptor and chemoreceptor inputs.