Norepinephrine activates potassium conductance in neurons of the turtle cerebral cortex

Brain Res. 1992 Jan 20;570(1-2):42-8. doi: 10.1016/0006-8993(92)90561-m.

Abstract

Whole-cell voltage and current clamp recordings were obtained from cortical neurons of the pond turtle, Pseudemys scripta elegans. Norepinephrine (NE) induced an outward current in 50% of pyramidal neurons. This current had a reversal potential of -88.3 +/- 3.2 mV, consistent with a K+ conductance increase, and had a mean amplitude of 18.3 +/- 7.2 pA at -40 mV. The ionic dependence and pharmacological analyses are both consistent with alpha 2 adrenergic receptor stimulation. Inhibition of Na(+)-dependent action potentials with TTX did not diminish the NE-induced K+ conductance, indicating that NE acts directly on the postsynaptic neuron. In addition to effects on postsynaptic conductance, NE dramatically decreased the amplitude of spontaneous inhibitory postsynaptic currents (IPSCs) in 55% of pyramidal neurons. The decrease in spontaneous IPSCs was observed both in those neurons which exhibited an increase in K+ conductance in response to NE administration (81%) and in those which did not (33%). Thus, NE modulates neuronal excitability both directly by activating a postsynaptic K+ conductance and indirectly by decreasing spontaneous IPSCs.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials / drug effects
  • Animals
  • Cerebral Cortex / cytology
  • Cerebral Cortex / drug effects*
  • Electric Conductivity / drug effects
  • Evoked Potentials / drug effects
  • Neurons / drug effects*
  • Norepinephrine / pharmacology*
  • Potassium / physiology*
  • Tetrodotoxin / pharmacology
  • Turtles / physiology*

Substances

  • Tetrodotoxin
  • Potassium
  • Norepinephrine