Two distinct serotonin neuron groups respond differently to a common antidepressant, with early changes linked to side effects and later changes to therapeutic benefits.
New research from Stockholm University sheds light on the molecular mechanisms behind SSRI treatment. Using spatial transcriptomics, scientists mapped gene activity in the Dorsal Raphe Nucleus of the brain after both short-term and long-term exposure to the SSRI fluoxetine.
Key Findings
The study identified two distinct subpopulations of serotonin neurons that responded to the drug in opposite ways over time.
- One group showed a significant increase in the expression of prodynorphin (Pdyn) after short-term treatment. This effect diminished with longer exposure. Notably, Pdyn signaling has been linked to stress-induced depressive symptoms.
- A second group expressed thyrotropin-releasing hormone (TRH) after prolonged treatment. TRH signaling has been linked to anti-depressive functions.
Interpretation
Researchers suggest the early Pdyn increase could be associated with negative side effects at the start of SSRI treatment, while the later TRH increase may relate to therapeutic effects that emerge after weeks.
The study provides molecular candidates for further research into depression mechanisms and antidepressant development.