Deep in the hippocampus, a molecular miscommunication is strangling memory. Long before a person with Alzheimer’s disease forgets a name or loses track of a familiar face, their neurons are already caught in a kind of biochemical traffic jam: too much inhibition, too little signal, a brain that has been braked so hard it can barely move.
Researchers at the University of Galway now think they can ease that brake, not by accelerating the system the way most current drugs attempt, but by targeting the very mechanism that’s pressing it down. The approach is counterintuitive. It may also be one of the most promising shifts in Alzheimer’s therapeutics in years.
Most drugs for Alzheimer’s disease target the excitatory side of the brain’s signalling equation, the circuitry that fires neurons and propels signals forward. They’ve been doing so, largely, for decades. The results have been modest at best; symptomatic improvements, marginal and temporary, with nothing to slow the disease itself. What the Galway team is focusing on instead is the inhibitory side: the neurons and receptors that quieten the brain, dampen signals, and regulate the delicate balance between too much and too little activity.
That balance, it turns out, is catastrophically disrupted in Alzheimer’s. The culprit is amyloid beta, the protein fragment that clumps into plaques in the diseased brain. Amyloid beta overstimulates neurons, triggering a kind of frantic compensatory response: inhibitory cells ramp up activity to try to dampen the storm. One result is an excess of GABA, the brain’s primary inhibitory neurotransmitter, flooding regions of the hippocampus where it’s not supposed to be. “We know, for sure, that the amino acid, GABA, is involved in many important physiological functions of the brain, including being the primary inhibiting factor for nerve cells,” says Professor Andrea Kwakowsky, who led the research. “However, in Alzheimer’s disease, this control that it helps to exert in the brain is compromised, contributing to cognitive decline and memory impairment.”
The specific receptor subtype Kwakowsky’s team focused on, called the alpha-5 GABA type A receptor, is found in unusually high concentrations in the hippocampus, accounting for something like a quarter or more of all GABA receptors there. In healthy brains, these receptors play an important role in learning and memory. In Alzheimer’s disease, amyloid beta causes them to become overactive, producing a sustained background inhibition, a tonic conductance, that essentially clamps down hippocampal neurons and prevents the kind of synaptic strengthening known as long-term potentiation, the cellular mechanism that underlies memory formation.
A Drug That Quiets the Silencer
The team’s solution was to use a compound called alpha-5IA, an inverse agonist that selectively blocks this particular receptor subtype. Inverse agonists are a somewhat unusual pharmacological tool; rather than simply blocking a receptor (as an antagonist would) or activating it (an agonist), they push the receptor’s activity below its baseline level. In this context, that means reducing the excessive tonic inhibition, letting the hippocampal network breathe again. In hippocampal slices treated with amyloid beta, the drug fully restored long-term potentiation to control levels. The silencer had been quieted.
“Our research is significant in that it demonstrates that if we block this GABA receptor activity in nerve cells we can reverse Alzheimer-like effects caused by amyloid beta and improve cognitive performance,” Kwakowsky said. The in vivo results were equally striking, at least for memory. Aged mice that had received hippocampal injections of amyloid beta and then been treated with alpha-5IA for 30 days performed significantly better on several spatial memory tests, including a classic maze navigation task, than untreated animals. “Our research is looking at the possibility of a therapy which helps to restore a balance in the brain after nerve cells have reacted to Alzheimer’s,” she added.
The mechanism behind these cognitive improvements seems to involve the restoration of tonic inhibitory conductance to something closer to normal. Patch clamp recordings from hippocampal slices taken from amyloid-injected mice showed dramatically elevated tonic conductance compared to healthy controls; after treatment with alpha-5IA, those levels fell back to roughly normal. The drug wasn’t just masking symptoms, in other words. It was, at least in this model, correcting the underlying electrophysiological disruption.
Where the Picture Gets Complicated
There is a significant caveat, though, and the researchers are admirably candid about it. While alpha-5IA improved memory in the mice, it did not rescue the pyramidal neurons that were lost following amyloid beta injection. The cells kept dying. Which suggests the drug might be compensating for neuronal loss rather than preventing it, an important distinction that will need to be resolved before anyone gets too excited about clinical translation. There’s also the small matter of renal toxicity: prolonged high-dose use of alpha-5IA in animal models has been associated with kidney damage, which somewhat limits its immediate prospects as a therapeutic candidate.
The team acknowledges that cleaner alternatives exist. Basmisanil, another alpha-5 GABA receptor negative allosteric modulator, has already completed Phase II clinical trials and shown a favourable safety profile (in a Down syndrome population, admittedly, rather than an Alzheimer’s one). ONO-8590580 is another candidate with preclinical evidence. Neither has been tested specifically in Alzheimer’s disease, but the Galway findings arguably provide a strong mechanistic rationale to do so.
Flipping the Field
What makes the study notable beyond its specific results is the conceptual shift it represents. For decades, Alzheimer’s research has been dominated by attempts to reduce excitatory damage, targeting glutamate signalling, acetylcholine depletion, amyloid plaques themselves. The GABAergic system has been something of an afterthought, even though evidence of its disruption in the disease has been accumulating for years. “Given the ever-increasing burden of Alzheimer’s disease, the urgent need for the identification of novel targets for the development of disease-modifying therapy is clear,” says Kwakowsky. What her team’s work offers is a plausible mechanism for why targeting inhibitory neurotransmission might actually do something that excitatory-focused drugs have failed to do: restore function rather than merely slow decline.
Whether that turns out to be true in human patients remains, of course, entirely unknown. Animal models of Alzheimer’s are notorious for failing to translate to human benefit. But the electrophysiology here is unusually detailed, the behavioral effects are robust, and the mechanistic story is coherent in a way that a lot of Alzheimer’s hypotheses frankly are not. The brake analogy might be imperfect but there’s something to it. The question now is whether the field will press down on the accelerator.
DOI: 10.1016/j.neuropharm.2026.110892
Frequently Asked Questions
What is the alpha-5 GABA receptor and why does it matter in Alzheimer’s disease?
The alpha-5 GABA type A receptor is a subtype of the brain’s main inhibitory receptor, found in particularly high concentrations in the hippocampus, the region central to learning and memory. In Alzheimer’s disease, amyloid beta causes these receptors to become overactive, producing a sustained braking signal that suppresses the synaptic strengthening needed to form memories. Because they’re concentrated exactly where Alzheimer’s does its worst cognitive damage, they’ve become an attractive therapeutic target.
How does this approach differ from existing Alzheimer’s drugs?
Most approved Alzheimer’s medications target the excitatory side of brain signalling, attempting to boost acetylcholine or reduce glutamate-driven damage. They’ve delivered modest symptomatic benefits at best, without slowing the disease. The University of Galway approach targets inhibitory signalling instead, specifically the overactive braking mechanism that compounds the harm done by amyloid beta. The idea is that restoring the brain’s excitatory/inhibitory balance may rescue cognitive function in a way that pure excitatory-focused drugs cannot.
Did the drug actually reverse memory loss in the study?
In mice with amyloid beta-induced hippocampal damage, treatment with alpha-5IA for 30 days produced significantly better performance on several long-term spatial memory tests compared to untreated animals. Importantly, memory-related brain activity, specifically long-term potentiation, was also restored in isolated brain slices. However, the drug did not prevent neuron death in the hippocampus, suggesting it may compensate for existing damage rather than stop the underlying disease process.
What are the main obstacles to using this approach in humans?
Alpha-5IA itself carries a known risk of kidney toxicity with prolonged high-dose use, which would be a serious concern in a disease that requires long-term treatment. The study was also conducted in mouse models, which have a poor track record of predicting human Alzheimer’s outcomes. Researchers point to newer compounds such as basmisanil as potentially safer alternatives worth testing, though none have yet been trialled specifically in Alzheimer’s patients.
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