CO(2)/H(+) chemoreception in the cat pre-Bötzinger complex in vivo
I C Solomon1, N H Edelman, M H O'Neal
1Department of Physiology and Biophysics, State University of New York at Stony Brook, 11794-8661, USA. ICSolomon@physiology.pnb.sunysb.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|June 14, 2000
Summary
Focal tissue acidosis in the pre-Bötzinger complex (pre-BötC) increases phrenic nerve activity, affecting respiratory rhythm and pattern. This suggests the pre-BötC is intrinsically chemosensitive and plays a role in respiratory control.
Area of Science:
- Neuroscience
- Respiratory Physiology
- Chemosensation
Background:
- The pre-Bötzinger complex (pre-BötC) is identified as a key respiratory rhythm generator in the brainstem.
- Chemosensitive regions in the brainstem detect changes in CO(2)/H(+) to regulate breathing.
- Previous studies on brainstem chemosensitive sites primarily showed amplitude changes in phrenic nerve activity.
Purpose of the Study:
- To investigate the effects of focal tissue acidosis within the pre-BötC on phrenic nerve discharge.
- To determine if the pre-BötC exhibits intrinsic chemosensitivity.
- To explore the role of the pre-BötC in modulating respiratory rhythm and pattern.
Main Methods:
- Unilateral microinjection of carbonic anhydrase inhibitors (acetazolamide or methazolamide) into the pre-BötC of anesthetized, ventilated cats.
- Recording and analysis of phrenic nerve discharge to assess changes in amplitude, frequency, and burst patterns.
- Comparison of the time course of effects between acetazolamide and methazolamide.
Main Results:
- Microinjection of acetazolamide and methazolamide into the pre-BötC reversibly increased the peak amplitude of phrenic nerve discharge.
- Increased burst frequency and the occurrence of premature (doublet) bursts were observed in response to pre-BötC acidosis.
- Effects were observed within 5-15 minutes, with acetazolamide showing faster onset and recovery than methazolamide.
Conclusions:
- Focal tissue acidosis in the pre-BötC alters respiratory rhythm and pattern, not just amplitude.
- These findings support the intrinsic chemosensitivity of the pre-BötC.
- The pre-BötC plays a significant role in the modulation of respiratory control in response to changes in CO(2)/H(+) levels.
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