The serotonergic inhibitory postsynaptic potential in prepositus hypoglossi is mediated by two potassium currents

Daniel H. Bobker, John Williams

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Synaptic inhibition mediated by the activation of potassium channels has been reported from several types of neurons. In each case, despite mediation by different neurotransmitters, the K+ conductance underlying the synaptic potential is activated by a G protein and inwardly rectifies. We report here a second K+ current that contributes to synaptic inhibition. Intracellular recordings were made from guinea pig nucleus prepositus hypoglossi in vitro, where we have described a 5-HT-mediated IPSP. Voltage-clamp analysis of the current induced by applied 5-HT revealed two separate conductances: an inwardly rectifying, rapidly activating K+ current (I(IR)) and an outwardly rectifying, slowly activating K+ current (I(OR)). I(IR) was blocked by extracellular Ba2+ (200 μM) and TEA+ (126 mM). I(OR) was insensitive to this concentration of Ba2+ and TEA+, but was inhibited by Cd2+ and intracellular BAPTA, indicating Ca dependence. Single focal electrical stimuli evoked a 5-HT-mediated IPSP, or under voltage clamp, an inhibitory postsynaptic current (IPSC). Ba2+ blocked only a component of this IPSC, which corresponded to the current caused by I(IR). When multiple stimuli were applied (to prolong the release of transmitter), the time-dependent current I(OR). was more fully activated, resulting in an augmentation of the IPSC. We conclude that the IPSC is caused by both currents and that its amplitude can be modulated by the degree to which I(OR) is activated. This represents a mechanism by which synaptic responses can be potentiated.

Original languageEnglish (US)
Pages (from-to)223-229
Number of pages7
JournalJournal of Neuroscience
Volume15
Issue number1 I
StatePublished - Jan 1995

Fingerprint

Inhibitory Postsynaptic Potentials
Potassium
Serotonin
Synaptic Potentials
Potassium Channels
GTP-Binding Proteins
Neurotransmitter Agents
Guinea Pigs
Neurons

Keywords

  • 5-HT
  • Ca-dependent K current
  • inhibitory postsynaptic potential
  • inward rectifier
  • outward rectifier
  • potassium channels

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

The serotonergic inhibitory postsynaptic potential in prepositus hypoglossi is mediated by two potassium currents. / Bobker, Daniel H.; Williams, John.

In: Journal of Neuroscience, Vol. 15, No. 1 I, 01.1995, p. 223-229.

Research output: Contribution to journalArticle

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