Functional rundown of gamma-aminobutyric acidA receptors in human hypothalamic hamartomas

Guohui Li, Kechun Yang, Chao Zheng, Qiang Liu, Yongchang Chang, John F. Kerrigan, Jie Wu

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Objective Human hypothalamic hamartomas (HHs) are highly associated with treatment-resistant gelastic seizures. HHs are intrinsically epileptogenic, although the basic cellular mechanisms responsible for seizure activity are unknown. Altered gamma-aminobutyric acid (GABA) function can contribute to epileptogenesis in humans and animal models. Recently, functional GABA A receptor (GABAAR) rundown has been described in surgically resected human temporal lobe epilepsy tissue. We asked whether functional GABAAR rundown also occurs in human HH neurons. Methods GABAAR-mediated currents were measured using perforated patch-clamp recordings in single neurons acutely dissociated from surgically resected HH tissue. In addition, functional GABAARs were expressed in Xenopus oocytes after microinjection with membrane fractions from either HH or control hypothalamus, and were studied with 2-electrode voltage-clamp recordings. Results Perforated patch-clamp recordings in dissociated HH neurons showed that repetitive exposure to GABA (5 consecutive exposures to 0.1 mM GABA with 1-second duration and at 20-second intervals) induced a time-dependent rundown of whole-cell currents in small HH neurons, whereas large HH neurons showed much less rundown using the same protocol. Functional rundown was not observed in HH neurons with repetitive exposure to glycine or glutamate. Two-electrode voltage-clamp recordings (6 consecutive exposures to 1 mM GABA with 10-second duration and at 40-second intervals) induced GABA current rundown in Xenopus oocytes microinjected with HH membrane proteins, but not in the oocytes expressing hypothalamic membrane proteins derived from human autopsy controls. Functional rundown of GABA currents was significantly attenuated by intracellular application of adenosine triphosphate or the nonspecific phosphatase inhibitor, okadaic acid. Interpretation Neurons from surgically resected human HH demonstrate functional rundown of GABAAR-mediated transmembrane currents in response to GABA agonist exposure. Rundown may be a marker for impaired GABAergic function and a contributing mechanism for seizure genesis within HH tissue.

Original languageEnglish (US)
Pages (from-to)664-672
Number of pages9
JournalAnnals of Neurology
Volume69
Issue number4
DOIs
StatePublished - Mar 2011
Externally publishedYes

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

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