Journal
BMC NEUROSCIENCE
Volume 16, Issue -, Pages -Publisher
BMC
DOI: 10.1186/s12868-015-0148-4
Keywords
gamma-aminobutyric acid; GABA(A) receptors; alpha 4 beta 1 delta subtype; Extrasynaptic receptors; beta 1 subunit
Categories
Funding
- Lundbeck Foundation [R83-A8000]
- Drug Research Academy
- Lundbeck Foundation [R139-2012-12270, R83-2011-8000] Funding Source: researchfish
- Medical Research Council [MR/K005537/1] Funding Source: researchfish
- MRC [MR/K005537/1] Funding Source: UKRI
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Background: GABA(A) receptor subunit composition has a profound effect on the receptor's physiological and pharmacological properties. The receptor beta subunit is widely recognised for its importance in receptor assembly, trafficking and post-translational modifications, but its influence on extrasynaptic GABA(A) receptor function is less well understood. Here, we examine the pharmacological properties of a potentially native extrasynaptic GABA(A) receptor that incorporates the beta 1 subunit, specifically composed of alpha 4 beta 1 delta and alpha 4 beta 1 subunits. Results: GABA activated concentration-dependent responses at alpha 4 beta 1 delta and alpha 4 beta 1 receptors with EC50 values in the nanomolar to micromolar range, respectively. The divalent cations Zn2+ and Cu2+, and the beta 1-selective inhibitor salicylidine salicylhydrazide (SCS), inhibited GABA-activated currents at alpha 4 beta 1 delta receptors. Surprisingly the alpha 4 beta 1 receptor demonstrated biphasic sensitivity to Zn2+ inhibition that may reflect variable subunit stoichiometries with differing sensitivity to Zn2+. The neurosteroid tetrahydro-deoxycorticosterone (THDOC) significantly increased GABA-initiated responses in concentrations above 30 nM for alpha 4 beta 1 delta receptors. Conclusions: With this study we report the first pharmacological characterisation of various GABA(A) receptor ligands acting at murine alpha 4 beta 1 delta GABA(A) receptors, thereby improving our understanding of the molecular pharmacology of this receptor isoform. This study highlights some notable differences in the pharmacology of murine and human alpha 4 beta 1 delta receptors. We consider the likelihood that the alpha 4 beta 1 delta receptor may play a role as an extrasynaptic GABA(A) receptor in the nervous system.
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