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Self-administration of morphine by rats causes monoamine release in the anterior cingulate cortex
S K Sudakov1, I V Rusakova, M M Trigub
1National Research Center of Narcology, Federal Agency for Health Care and Social Development. s-sudakov@mail.ru
Abstract:
Monoamine content in the microdialysate from the anterior cingulate cortex was measured in rats after injections and self-administration of morphine. Forced intraperitoneal injection of morphine did not lead to appreciable changes in the monoamine levels in the dialysate. Self-administration significantly increased monoamine levels in the extracellular space of the anterior cingulate cortex. Changes in catecholamine levels in the extracellular space of the anterior cingulate cortex correlated with the intensity of self-administration. The more morphine the animals injected to themselves, the greater was the increment in dopamine and norepinephrine levels. It seems that the increase of serotonin content in the anterior cingulate cortex did not depend on blood morphine concentration, but just reflected the fact of narcotic self-administration. The release of serotonin from nerve endings in the anterior cingulate cortex gradually increased at the beginning of the session, after which serotonin concentration started to decrease. The results indicate that monoamines are released from nerve endings in the anterior cingulate cortex only in response to self-administration of morphine. Catecholamines were released after each self-administration of the narcotic, while serotonin release seemed to be associated with the general status of the animal realizing this behavior.
Insights
Morphine self-administration, unlike injection, significantly elevates monoamine levels in the rat anterior cingulate cortex. Dopamine and norepinephrine release correlates with intake, while serotonin release reflects the behavior itself.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- The anterior cingulate cortex (ACC) plays a crucial role in reward processing and addiction.
- Understanding the neurochemical changes associated with drug self-administration is vital for addiction research.
Purpose of the Study:
- To investigate the impact of morphine administration routes on monoamine levels in the rat ACC.
- To explore the relationship between morphine self-administration intensity and changes in specific monoamines.
Main Methods:
- Microdialysis was used to measure monoamine content (dopamine, norepinephrine, serotonin) in the rat ACC.
- Rats underwent either forced intraperitoneal injection or voluntary self-administration of morphine.
- Correlation analysis was performed between drug intake and monoamine levels.
Main Results:
- Forced morphine injection did not alter ACC monoamine levels.
- Morphine self-administration significantly increased extracellular dopamine, norepinephrine, and serotonin in the ACC.
- Dopamine and norepinephrine increases correlated positively with the amount of morphine self-administered.
- Serotonin level changes appeared linked to the act of self-administration rather than blood morphine concentration.
Conclusions:
- Monoamine release in the ACC is specifically triggered by the active behavior of morphine self-administration.
- Catecholamine release is associated with individual drug intake events.
- Serotonin release may reflect the overall behavioral engagement in drug-seeking and taking.
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