The role of intrinsic and agonist-activated conductances in determining the firing patterns of preoptic area neurons in the guinea pig

Edward J. Wagner, Cruz Reyes-Vazquez, Oline K. Rønnekleiv, Martin J. Kelly

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Whole-cell and intracellular recordings were made in coronal hypothalamic slices prepared from ovariectomized female guinea pigs. 62% of preoptic area (POA) neurons fired action potentials in a bursting manner, and exhibited a significantly greater afterhyperpolarization (AHP) than did non-bursting POA neurons. The majority (70%) of POA neurons (n=76) displayed a time-dependent inward rectification (Ih) that was blocked by CsCl (3 mM) or by ZD 7288 (30 μM). In addition, 51% of the cells expressed a low-threshold spike (LTS) associated with a transient inward current (IT) that was blocked by NiCl2 (200 μM). A smaller percentage of POA neurons (29%) expressed a transient outward, A-type K+ current that was antagonized by a high concentration of 4-aminopyridine (3 mM). Moreover, POA neurons responded to bath application of the μ-opioid receptor agonist DAMGO (93%) or the GABA(B) receptor agonist baclofen (83%) with a membrane hyperpolarization or an outward current. These responses were accompanied by a decrease in input resistance or an increase in conductance, respectively, and were attenuated by BaCl2 (100 μM). In addition, the reversal potential for these responses closely approximated the Nernst equilibrium potential for K+. These results suggest that POA neurons endogenously express to varying degrees an AHP, an Ih, an IT and an A-type K+ current. The vast majority of these neurons also are inhibited upon μ-opioid or GABA(B) receptor stimulation via the activation of an inwardly-rectifying K+ conductance. Such intrinsic and transmitter-activated conductances likely serve as important determinants of the firing patterns of POA neurons.

Original languageEnglish (US)
Pages (from-to)29-41
Number of pages13
JournalBrain research
Volume879
Issue number1-2
DOIs
StatePublished - Oct 6 2000

Keywords

  • Afterhyperpolarization
  • Calcium current
  • Firing
  • Inward rectification
  • Preoptic area

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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