Inhibition of thalamic excitability by 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-3-ol: a selective role for delta-GABA(A) receptors

Murray B. Herd, Nicola Foister, Dev Chandra, Dianne R. Peden, Gregg E. Homanics, Verity J. Brown, David J. K. Balfour, Jeremy J. Lambert, Delia Belelli (Lead / Corresponding author)

    Research output: Contribution to journalArticlepeer-review

    56 Citations (Scopus)

    Abstract

    The sedative and hypnotic agent 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-3-ol (THIP) is a GABA(A) receptor (GABA(A)R) agonist that preferentially activates delta-subunit-containing GABA(A)Rs (delta-GABA(A)Rs). To clarify the role of delta-GABA(A)Rs in mediating the sedative actions of THIP, we utilized mice lacking the alpha(1)- or delta-subunit in a combined electrophysiological and behavioural analysis. Whole-cell patch-clamp recordings were obtained from ventrobasal thalamic nucleus (VB) neurones at a holding potential of -60 mV. Application of bicuculline to wild-type (WT) VB neurones revealed a GABA(A)R-mediated tonic current of 92 +/- 19 pA, which was greatly reduced (13 +/- 5 pA) for VB neurones of delta(0/0) mice. Deletion of the delta- but not the alpha(1)-subunit dramatically reduced the THIP (1 mu m)-induced inward current in these neurones (WT, -309 +/- 23 pA; delta(0/0), -18 +/- 3 pA; alpha(0/0)(1), -377 +/- 45 pA). Furthermore, THIP selectively decreased the excitability of WT and alpha(0/0)(1) but not delta(0/0) VB neurones. THIP did not affect the properties of miniature inhibitory post-synaptic currents in any of the genotypes. No differences in rotarod performance and locomotor activity were observed across the three genotypes. In WT mice, performance of these behaviours was impaired by THIP in a dose-dependent manner. The effect of THIP on rotarod performance was blunted for delta(0/0) but not alpha(0/0)(1) mice. We previously reported that deletion of the alpha(1)-subunit abolished synaptic GABA(A) responses of VB neurones. Therefore, collectively, these findings suggest that extrasynaptic delta-GABA(A)Rs vs. synaptic alpha(1)-subunit-containing GABA(A)Rs of thalamocortical neurones represent an important molecular target underpinning the sedative actions of THIP.

    Original languageEnglish
    Pages (from-to)1177-1187
    Number of pages11
    JournalEuropean Journal of Neuroscience
    Volume29
    Issue number6
    DOIs
    Publication statusPublished - Mar 2009

    Keywords

    • extrasynaptic receptors
    • gaboxadol
    • sedation
    • thalamus
    • THIP
    • tonic inhibition
    • EXTRASYNAPTIC GABA(A) RECEPTORS
    • SUBUNIT-CONTAINING RECEPTORS
    • CEREBRAL-BLOOD-FLOW
    • DELTA-SUBUNIT
    • GRANULE CELLS
    • PHARMACOLOGICAL CHARACTERIZATION
    • THALAMOCORTICAL NEURONS
    • MEDIATED CONDUCTANCE
    • TONIC INHIBITION
    • DENTATE GYRUS

    Cite this