Rethinking Dopamine - Brain Stimulation - Aging Cells - GLP1 Pills?

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Mar 19, 2026, 6:33:05 AMMar 19

https://www.nature.com/articles/d41586-026-00836-x

Dopamine takes a hit: how neuroscience is rethinking the ‘feel-good’ chemical

David Adam

When neuroscientists gather in the Spanish city of Seville in May for the annual Dopamine Society meeting, one discussion could be unusually lively. Session 31 will feature a debate between researchers who fundamentally disagree about the role dopamine has in the brain.

Dopamine is one of the most extensively studied neurotransmitters, chemicals that convey signals from cell to cell. It’s the one with the highest profile outside neuroscience: often known as the ‘pleasure chemical’, it’s depicted as the hit of reward that people get from recreational drugs or scrolling through social media.

That’s a gross simplification of what dopamine does; on that, researchers agree. But beyond that, where once there was a simple model that explained how dopamine works in the brain, now there are challenges that seek to amend the theory — or even to overturn it.

This could have implications not only for basic neuroscience, but also for clinicians trying to explain and treat conditions such as attention deficit hyperactivity disorder (ADHD) and addiction. If the model is wrong or needs modification, then so might some of the assumptions about what drives these disorders and the best way to treat them.

The classic idea, known as the reward prediction error (RPE) hypothesis, is that bursts of dopamine in the brain link stimuli to rewards, helping to reinforce associations that fulfil a need for an animal or a person. The model has dominated and guided research in the field for decades, offering a mathematical framework to interpret data from animal experiments, and it does a good job of explaining behaviour.

This was a valuable rarity for researchers struggling to overlay simple theories onto the intense complexity of the brain. “Dopamine was the one field of neuroscience where we had a computational model that explained what the signal was and what it was computing,” says Mark Humphries, a neuroscientist at the University of Nottingham, UK. People in the field knew that some of the assumptions involved in the RPE model were simplistic. But as a working understanding of part of the brain, it was seen as a major step forwards.

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https://www.science.org/content/article/colliding-currents-can-target-deep-brain-without-surgery

Colliding currents can target the deep brain without surgery

By Jennie Erin Smith

In 2017, physicist Nir Grossman made a discovery that promised a versatile new way to manipulate the living brain. Working in mice, he and his collaborators applied two high-frequency electrical currents to the skull. At the spot in the rodents’ brains where the currents collided, the electric field altered neural activity. Other noninvasive methods typically reach no further than the cortex, the brain’s outer layer. The new approach, called temporal interference (TI) stimulation, offered access to deep-brain areas previously only targetable with surgery.

Neuroscientists were quick to see TI’s potential for studying the brain and treating its disorders, and they are now testing it in a variety of human trials. Although the studies are still small and many have not been replicated, they hint that TI may have potential to ease epilepsy symptoms, help stroke patients recover movement, boost memory in people with Alzheimer’s disease, and treat psychiatric conditions.

Many say TI—which uses two pairs of head-mounted electrodes linked to portable current generators—is nimbler and likely safer than transcranial focused ultrasound, another emerging technology that can modulate deep-brain regions without surgery. And because TI equipment is inexpensive and widely available, it’s been easy for labs to try out.

“What [TI] should be is an open-source therapy,” says physicist and epilepsy researcher Adam Williamson of St. Anne’s University Hospital. This year, he and his colleagues showed in a pilot study of people with epilepsy that TI stimulation to the hippocampus, a deep-brain structure that is often the source of hard-to-treat seizures, could both suppress spikes of abnormal brain activity and improve participants’ sleep. His group and another at Duke University are collaborating on a larger clinical trial of the approach.

In TI, two high-frequency electrical currents applied to the brain meet or interfere to form a low-frequency focal area, or “envelope,” that can boost or suppress the rate of neurons’ electrical signaling. “It’s a powerful way to entrain neuronal activity,” says Melanie Boly, an epilepsy researcher at the University of Wisconsin–Madison.

https://www.thetransmitter.org/aging/signs-of-aging-vary-across-brain-cells/

Signs of aging vary across brain cells

By Claudia López Lloreda

As cells age and acquire damage, they stop dividing and enter a comatose-like state. This natural process, called senescence, has several classic hallmarks, including the expression of cell cycle arrest genes and enlarged nuclei, and can spread among neighboring cells. But senescence arises and expands differently across human brain cell types and in response to various stressors, two new studies suggest.

“We’re living in the new world of the senescence field,” says Joseph Herdy, investigator at the Salk Institute for Biological Studies, who was not involved with the work. Any cell type, it seems, can senesce under the right conditions, he adds, but each responds in its own way, complicating the picture.

Human brain cell lines—neurons, astrocytes, microglia, oligodendrocytes and endothelial cells—present cell-type-specific responses to stressors that trigger senescence, according to one of the new studies, published in Nature Communications in December. And like senescent cells elsewhere in the body, some—though not all—brain cells can release molecules that spread the senescent phenotype to other cells, according to the other study, a preprint posted on bioRxiv last month.

These cell-type-specific differences may reflect the various ways cells acquire and enter a state of senescence, says Jalees Rehman, professor of biochemistry and molecular genetics at the University of Illinois, who was not involved with either work. “They might all have some shared universal features, such as no more cell cycle, some degree of inflammation, but maybe the path of how you get there might be different between cell types.”

Senescent cells are sparse and difficult to find in the brain, says Markus Riessland, assistant professor of neurobiology and behavior at Stony Brook University and an investigator on both new studies. So to study the cell-type specificity, Riessland and his colleagues decided to induce senescence in different cells in culture. “Otherwise, if you only have one cell, there’s no way you could characterize how the cell goes into senescence and what the difference between the senescent cells are,” he says.

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https://www.nature.com/articles/d41586-026-00856-7

Can weight-loss pills replace injectables? What the science says

Mariana Lenharo

The weight-loss drugs that took the world by storm a few years ago have a drawback for anyone afraid of needles: they must be injected weekly. But scientists have been racing to perfect anti-obesity pills — which are now coming to market.

An oral anti-obesity drug called orforglipron is likely to be approved by US regulators by the end of April, pharmaceutical analysts say. In December, a pill version of the obesity drug semaglutide won US regulatory approval. Both drugs belong to the class of therapies called glucagon-like peptide-1 (GLP-1) receptor agonists. Semaglutide, sold as Wegovy, is made by Novo Nordisk in Bagsværd, Denmark; orforglipron is made by Eli Lilly and Company in Indianapolis, Indiana.

Clinical-trial results have been positive. After around one year of treatment at the highest dosage, people taking orforglipron lost, on average, about 11% of their body weight1, and those taking semaglutide pills lost almost 14%2.

But it’s uncertain whether pills could one day replace the GLP-1 pens that have become a weight-loss staple. Oral drugs face formidable developmental challenges, and several injected drugs cause greater weight loss than does either orforglipron or oral semaglutide: the approved injectable drug Zepbound, for example, leads to weight loss of up to 21% of body weight3. “It’s encouraging, and it’s fantastic to have double-digit weight loss with a pill,” says Daniel Drucker, an endocrinologist at the University of Toronto in Canada. “But so far, rather than replace, I would say they’re going to complement the options that we have.”

There’s a good reason why the original GLP-1 receptor agonists, which mimic the natural hormone glucagon-like peptide-1, were sold in injectable form. The drugs are composed of peptides, which are relatively large molecules. Because of their size, digestive enzymes quickly break them down, and the intestinal lining limits their entry into the bloodstream.