title: Acetazolamide on the ventral medulla of the cat increases phrenic output and delays the ventilatory response to CO2.
abstract: 1. Acetazolamide (0.1 mM) applied to the surface of the rostral ventrolateral medulla or microinjected beneath the medullary surface in chloralose-urethane-anaesthetized, vagotomized, carotid-denervated, paralysed, servo-ventilated cats produced a long-lasting increase in integrated phrenic nerve activity. 2. Extracellular pH measured beneath the rostral ventrolateral medulla exhibited a long-lasting decrease after surface acetazolamide but was not a good predictor, in each individual animal, of changes in phrenic activity. 3. Medullary carbonic anhydrase inhibition reduced the slope and the half-time of the phrenic response to rapid step CO2 increases. Conversely, acetazolamide did not affect the phrenic response to steady-state CO2 increases. 4. These data indicate that localized inhibition of medullary carbonic anhydrase causes a centrally mediated increase in ventilation that we attribute to medullary tissue hypercapnia and acidosis. In addition, these data indicate that medullary carbonic anhydrase may play a role in central CO2 chemotransduction.
authors.affiliation: Department of Physiology, Dartmouth Medical School, Hanover, NH 03756.
authors.forename: E L
authors.initials: EL
authors.lastname: Coates
authors.forename: A H
authors.initials: AH
authors.lastname: Li
authors.forename: E E
authors.initials: EE
authors.lastname: Nattie
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology*; D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology*; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D002415:Cats; D005260:Female; D006863:Hydrogen-Ion Concentration; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects* / Q000201:enzymology; D010791:Phrenic Nerve / Q000502:physiology*; D012119:Respiration / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D013449:Sulfonamides; C037272:Cl 13850; D002245:Carbon Dioxide; D000086:Acetazolamide