New research offers a clearer picture of why progress has moved slowly and where it could accelerate.
Scientists at MIT and partner institutions have produced the first detailed atlas of neurons in the striatum. This brain region plays a central role in habit formation reward and addiction.
The map identifies 31 distinct neuron subgroups. Several populations also play direct roles in opioid response. The senior authors say they created the atlas to guide the next generation of drug development.
What the Researchers Mapped
The striatum sits deep within the brain and helps coordinate decision making, movement habit formation and reward processing. It also plays a major role in addiction and can suffer damage in conditions such as Huntington’s disease and schizophrenia.
The research team included Myriam Heiman of MIT’s Picower Institute, Manolis Kellis of CSAIL and the Broad Institute and Dana Gabuzda of Dana Farber. The researchers analyzed postmortem striatal tissue from brain banks in the United States and Canada.
They used single cell RNA sequencing, spatial transcriptomics and fluorescent in situ hybridization to examine the tissue.
The research produced a map containing 31 neuron subpopulations including nine types of medium spiny neurons. Two groups stand out for addiction treatment research.
The team calls one population D1 outliers. These cells showed high expression of genes involved in addiction and substance use disorder. They also showed particularly strong activity in genes linked to opioid response.
A second group known as D2 outliers showed strong expression of genes that respond to antidepressants.
Both populations responded strongly to clozapine. The drug can effectively treat psychotic disorders, but its use remains limited because it can cause a rare and potentially fatal blood disorder.
Researchers can now identify the specific cells that respond to clozapine. That knowledge could help scientists develop targeted drugs that preserve its therapeutic benefits while reducing its serious risks.
A Species Problem With Opioid Research
One finding carries immediate significance for researchers. The gene that encodes the mu opioid receptor known as OPRM1 shows high expression in human D1 outlier cells. The equivalent mouse neurons show very little of the gene.
That difference creates a problem, because researchers conduct much of their preclinical opioid research in mice. Mouse models may therefore overlook the very cells that play an important role in human opioid response.
Heiman says the research team can now reserve rodent models for genes that remain conserved across species. Researchers can also engineer more human like models for genes that differ substantially between humans and mice.
What This Means for Treatment Seekers
This research will not change the treatments available at a rehab center this year or next year. Drug development can take many years as researchers move from cell mapping through testing and eventually toward an approved medication.
The research does change what scientists can target. Medication development for opioid use disorder has long faced an incomplete picture of the brain cells involved in addiction.
Now researchers have a validated map of those cells. The atlas also identifies opioid receptor populations that mouse models largely missed. That gives pharmaceutical researchers a more precise list of potential targets.
For now the existing evidence base remains in place. Medications for opioid use disorder, behavioral therapies and structured treatment through accredited programs remain established approaches to care. These treatments can work especially well when providers combine them according to a patient’s needs.
Exploring Treatment Options
If you or someone you love is living with opioid use disorder or another addiction you do not need to wait for future medications before seeking help.
Rehab.com’s directory lets you compare rehab centers by location level of care, therapies and accepted insurance. You can research medication assisted treatment and verify facility credentials before you make a decision.
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