Lipopolysaccharide increases endogenous morphine levels in rat brain.

¹Neuroscience Research Institute, State University of New York, College at Old Westbury, NY 11568, USA.

|October 12, 2000

Summary

Lipopolysaccharide (LPS) injection and fasting significantly increase endogenous rat brain morphine levels. These findings indicate that the brain

Area of Science:

Background:

Endogenous morphine, also known as endomorphins, plays a role in pain modulation and stress responses.
Lipopolysaccharide (LPS) is a component of Gram-negative bacteria that can trigger inflammatory responses.

Purpose of the Study:

To investigate the effect of lipopolysaccharide (LPS) administration on endogenous morphine levels in the rat brain.
To determine the time course of changes in brain morphine levels following LPS injection.
To assess the impact of fasting on endogenous brain morphine levels.

Main Methods:

Quantification of endogenous brain morphine using high-performance liquid chromatography with electrochemical detection (HPLC-ECD).
Confirmation of morphine levels via gas chromatography-mass spectrometry (GC-MS).
Intraperitoneal injection of LPS (10 µg) in rats, with subsequent brain tissue analysis at various time points.

Main Results:

Baseline endogenous brain morphine levels were determined to be 7.0 ± 3.2 ng/g wet weight.
LPS injection led to a time-dependent increase in brain morphine levels, peaking at 36 hours post-injection.
After 72 hours, morphine levels rose significantly to 66.0 ± 5.4 ng/g (P<0.001).
A 96-hour fasting period also elevated brain morphine levels to 44.0 ± 3.6 ng/g.

Conclusions:

Organismic challenges, such as LPS exposure and fasting, can induce significant increases in endogenous brain morphine.
Rat brain morphinergic systems exhibit a notable latent period in their response to physiological stressors.
These findings highlight the brain's endogenous opioid system's involvement in responding to systemic challenges.

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