Nicotinic acetylcholine receptors in isolated type I cells of the neonatal rat carotid body

Neuroscience. 1993 May;54(1):275-81. doi: 10.1016/0306-4522(93)90399-z.

Abstract

Electrophysiological responses of enzymatically isolated type I cells from the neonatal rat carotid body to cholinergic agonists were examined using the whole-cell patch-clamp technique. Inward currents were evoked in cells clamped at -70 mV in response to bath-applied carbachol and two selective nicotinic agonists, nicotine and dimethylphenylpiperazinium. Muscarine failed to produce any change in membrane current. Responses to nicotine were concentration-dependent and also voltage-dependent, showing strong rectification positive to -40 mV. Currents evoked by nicotine were reduced or abolished in the presence of mecamylamine and also by high concentrations of atropine (10 or 100 microM). Under "current-clamp", nicotine was shown to depolarize type I cells, an effect which was only slowly reversible, but which could be rapidly attenuated by introduction of mecamylamine to the perfusate. In voltage-clamped cells, nicotine could evoke inward currents when extracellular Na+ was replaced by Ca2+. Our results demonstrate the presence of functional nicotinic acetylcholine receptors on type I cells of the neonatal rat carotid body. Activation of these receptors could lead to excitation of the intact carotid body by either of two possible mechanisms: depolarization of type I cells sufficient to open voltage-gated Ca2+ channels, or Ca2+ influx through the receptor pore itself. Either (or both) mechanisms could trigger catecholamine release from type I cells, which is a fundamental step in chemotransmission.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Calcium / metabolism
  • Carotid Body / cytology
  • Carotid Body / metabolism*
  • Carotid Body / physiology
  • Cell Separation
  • Electrophysiology
  • Nicotine / pharmacology
  • Osmolar Concentration
  • Parasympathomimetics / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Rats, Wistar
  • Receptors, Nicotinic / metabolism*

Substances

  • Parasympathomimetics
  • Receptors, Nicotinic
  • Nicotine
  • Calcium