Lithium Triggers Opioid Peptide Release in the Brain by Disabling Their Self-Regulation System | Research

The takeaway

Lithium stimulates the release of beta-endorphin, dynorphin, and met-enkephalin by disabling the autoreceptors that normally keep opioid release in check — with chronic use permanently inactivating some of these brakes.

Permanent autoreceptor inactivation
Chronic lithium treatment (10 days) permanently disabled the autoreceptors controlling dynorphin and met-enkephalin release, but not beta-endorphin

What the researchers found

Lithium releases all three opioid peptides by inhibiting autoreceptors. Chronic treatment permanently inactivates dynorphin and met-enkephalin autoreceptors through G-protein-dependent mechanisms.

Why it matters

This may partly explain how lithium stabilizes mood. By releasing opioid peptides and changing their regulation, lithium could affect mood, pain perception, and stress responses.

How the study worked

Rat hypothalamic slices were perfused with lithium and/or naloxone. Opioid peptide release was measured. Tetrodotoxin confirmed presynaptic action. Pertussis toxin tested G-protein involvement.

What this study cannot tell us

In-vitro hypothalamic slice study. Lithium concentrations used may not match therapeutic blood levels. The clinical significance of opioid release for bipolar disorder treatment is speculative.

How to read the evidence

Preliminary in-vitro study using rat brain slices. Mechanistically detailed but the clinical relevance to bipolar disorder treatment is speculative.

When this study was published

Published in 1990. Lithium's mechanism of action remains incompletely understood, and its interaction with the opioid system is one of many proposed pathways.

The bigger picture

This study offered a potential explanation for part of lithium's mood-stabilizing mechanism. If lithium permanently alters how the brain releases opioid peptides, this could contribute to its effects on mood, pain perception, and stress resilience. It connects psychiatric pharmacology to the endogenous opioid system.

Questions still open

Does lithium's opioid-releasing effect contribute to its anti-suicidal properties?
Are the mood-stabilizing and opioid effects of lithium separable?

Common questions

What are autoreceptors?

Autoreceptors are self-regulating sensors on nerve terminals. When opioid peptides accumulate, autoreceptors detect this and reduce further release — acting as a brake. Lithium disables this brake, allowing more opioid peptide release.

Could lithium's opioid effects explain its mood-stabilizing action?

Potentially in part. Opioid peptides influence mood, pain perception, and stress resilience. By permanently altering their release regulation, lithium may contribute to emotional stability — though its mood-stabilizing effects likely involve multiple pathways.

Read the original research

Stimulation of hypothalamic opioid peptide release by lithium is mediated by opioid autoreceptors: evidence from a combined in vitro, ex vivo study.

Neuroscience, 36(3), 691-7

View on PubMed ↗

Citation

Burns, G; Herz, A; Nikolarakis, K E. (1990). Stimulation of hypothalamic opioid peptide release by lithium is mediated by opioid autoreceptors: evidence from a combined in vitro, ex vivo study.. Neuroscience, 36(3), 691-7.