ATP-sensitive K+ channels are functional in expiratory neurones of normoxic cats

J Physiol. 1996 Jul 15;494 ( Pt 2)(Pt 2):399-409. doi: 10.1113/jphysiol.1996.sp021501.


1. We analysed spontaneously active expiratory neurones (n = 48) of anaesthetized cats for the presence of ATP-sensitive K+ (KATP) channels. 2. Intracellular injection of ATP reversibly depolarized neurones during all phases of the respiratory cycle. During expiration, membrane potential depolarized by an average of 1.5 +/- 0.1 mV leading to a 25% increase of discharge frequency. During inspiration, ATP induced a 1.8 +/- 0.2 mV depolarization, which was accompanied by a maximum of 20% increase of input resistance (Rn). 3. Extracellular application of diazoxide, an agonist of KATP channels, resulted in reversible membrane hyperpolarization in 68% of neurones (n = 19). This hyperpolarization (2.5 mV during expiration and 3.1 mV during inspiration) was accompanied by a 22% decrease in Rn. 4. Extracellular application of tolbutamide and glibenclamide, two antagonists of KATP channels, evoked reversible depolarizations in 76% of neurones (n = 21). The depolarization was relatively constant throughout the respiratory cycle (1.4 mV during expiration and 2.3 mV during inspiration). Rn increased by 22%. 5. The same sulphonylureas also changed the steepness of membrane depolarization when neurones escaped spontaneous synaptic inhibition during postinspiration. Extracellularly applied tolbutamide and glibenclamide increased the steepness of depolarization by 21%, while diazoxide reduced it by 20%. 6. Antagonism of drugs was verified by simultaneous extra- and intracellular application of diazoxide and glibenclamide, respectively. 7. During voltage clamp at holding potential at -60 to -67 mV, intracellular or extracellular application of tolbutamide and glibenclamide blocked a persistent outward current. 8. We conclude that KATP channels are functional in expiratory neurones of adult cats and contribute to the control of excitability even during normoxia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology*
  • Animals
  • Bicuculline / pharmacology
  • Blood-Brain Barrier
  • Brain Stem / physiology*
  • Cats
  • Female
  • Glyburide / pharmacology
  • Hypoxia
  • Male
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Neurons / drug effects
  • Neurons / physiology*
  • Phrenic Nerve / physiology*
  • Potassium Channels / drug effects
  • Potassium Channels / physiology*
  • Reference Values
  • Respiration / physiology*
  • Tolbutamide / pharmacology


  • Potassium Channels
  • Adenosine Triphosphate
  • Tolbutamide
  • Glyburide
  • Bicuculline