Okada Y, Kuwana SI, Kawai A, Mückenhoff K, Scheid P. Significance of extracellular potassium in central respiratory control studied in the isolated brainstem-spinal cord preparation of the neonatal rat.
Respir Physiol Neurobiol 2005;
146:21-32. [PMID:
15733776 DOI:
10.1016/j.resp.2004.10.009]
[Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2004] [Indexed: 10/26/2022]
Abstract
The significance of extracellular potassium in central respiratory control was investigated using the isolated brainstem-spinal cord preparation of the neonatal rat. Depth profiles of extracellular potassium activity ([K+])ECF in the medulla were measured with ion-sensitive microelectrodes. Although [K+]ECF increased with depth in medullary tissue during control (4 mM) and low (1 mM) potassium concentration ([K+])CSF superfusion, this gradient disappeared with higher [K+]CSF. With low [K+]CSF (1 mM), respiratory CO2 responsiveness was abolished, and increased with high [K+]CSF (8 mM). Respiratory frequency (fR) was diminished at low [K+]CSF (1 mM), and increased with elevated [K+]CSF (8 and 16 mM); with yet higher [K+]CSF (32 mM) apnea occurred after a transient increase in fR. Perforated patch recording revealed that high [K+]ECF decreased membrane resistance, depolarized membrane potential, and increased firing frequency in most of the recorded medullary neurons. High [K+]ECF also increased excitatory and inhibitory post-synaptic potentials of medullary neurons and augmented the functional connectivity among neurons. It is concluded that [K+]ECF is of importance in the maintenance of respiratory rhythm and central chemosensitivity.
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