DS2 is a novel and selective positive allosteric modulator of δ-subunit-containing GABAA receptors. DS2 enhances the function of extrasynaptic δ-GABAA receptors by increasing the maximal response to GABA, while acting via an unknown site to provide receptor subunit selectivity[1-2]. DS2 is used to study the function of extrasynaptic δ-GABAA receptors and their role in stroke recovery[3-4].
In vitro, HEK293 cells stably expressing the human δ subunit were co-incubated with DS2 (1–5μM) and GABA (EC₂₅–₃₅) to measure the current response. DS2 selectively potentiated the current response or fluorescence signal at δ-GABAA receptors (α₄β₁δ and α₄β₃δ)[5]. Mouse thalamic ventrobasal (VB) neurons and cerebellar granule cells (CGCs) were pretreated with DS2 (3–10µM) for 30 seconds before recording in the presence of ambient GABA. DS2 significantly enhanced the tonic inhibitory current mediated by δ-subunit-containing δ-GABAA receptors[6].
In vivo, in the AppNL-F KI AD mouse model aged 12-16 months, DS2 (1-4mg/kg) was administered via intraperitoneal injection once daily for 5 consecutive days. DS2 significantly reduced anxiety-like behaviors and normalized the expression of δ-GABAA receptors[7]. In male C57BL/6J mice after stroke, DS2 (0.1-4mg/kg) was administered via intraperitoneal injection twice, at 1 hour and 24 hours post-stroke. DS2 significantly reduced infarct volume, improved motor function in the grid-walking and cylinder tasks, and lowered the levels of circulating pro-inflammatory cytokines (TNF-α, IL-6, IL-17)[8].
References:
[1] Lee HJ, Absalom NL, Hanrahan JR, et al. A pharmacological characterization of GABA, THIP and DS2 at binary α4β3 and β3δ receptors: GABA activates β3δ receptors via the β3(+)δ(-) interface. Brain Res. 2016 Aug 1;1644:222-30.
[2] Jensen ML, Wafford KA, Brown AR, et al. A study of subunit selectivity, mechanism and site of action of the delta selective compound 2 (DS2) at human recombinant and rodent native GABA(A) receptors. Br J Pharmacol. 2013 Mar;168(5):1118-32.
[3] Jensen NN, Wilhelmsen KS, Jensen MH, et al. Exploring the DS2 Scaffold for GABAA Receptor Modulation: Progress toward the Development of a GABAA δ-Subunit Preferring Negative Allosteric Modulator. J Med Chem. 2026 Feb 26;69(4):3811-3832.
[4] Rostrup F, Falk-Petersen CB, Harpso E K, et al. Structural Determinants for the Mode of Action of Imidazopyridine DS2 at δ-Containing γ-Aminobutyric Acid Type A Receptors. J Med Chem. 2021 Apr 22;64(8):4730-4743.
[5] Falk-Petersen CB, Søgaard R, Madsen KL, et al. Development of a Robust Mammalian Cell-based Assay for Studying Recombinant α4 β1/3 δ GABAA Receptor Subtypes. Basic Clin Pharmacol Toxicol. 2017 Aug;121(2):119-129.
[6] Wafford KA, van Niel MB, Ma QP, et al. Novel compounds selectively enhance delta subunit containing GABA A receptors and increase tonic currents in thalamus. Neuropharmacology. 2009 Jan;56(1):182-9.
[7] Zhang W, Liu T, Li J, et al. Decreased extrasynaptic δ-GABAA receptors in PNN-associated parvalbumin interneurons correlates with anxiety in APP and tau mouse models of Alzheimer's disease. Br J Pharmacol. 2024 Oct;181(20):3944-3975.
[8] Neumann S, Boothman-Burrell L, Gowing EK, et al. The Delta-Subunit Selective GABA A Receptor Modulator, DS2, Improves Stroke Recovery via an Anti-inflammatory Mechanism. Front Neurosci. 2019 Oct 29;13:1133.