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Immunomodulating effects of morphine microinjected into periaqueductal gray
Zhongguo Yao Li Xue Bao = Acta Pharmacologica Sinica
|March 1, 1995
Summary
Morphine impacts the immune system via the periaqueductal gray (PAG) by suppressing natural killer cell activity and enhancing T-lymphocyte functions, mediated through opioid receptors.
Area of Science:
- Neuroimmunology
- Pharmacology
Background:
- The periaqueductal gray (PAG) is a midbrain region involved in pain modulation and autonomic control.
- Opioid receptors are widely distributed in the central nervous system, including the PAG.
Purpose of the Study:
- To investigate the immunomodulatory effects of morphine administered directly into the rat PAG.
- To determine the role of PAG opioid receptors in mediating morphine's influence on immune responses.
Main Methods:
- Morphine was microinjected into the rat PAG.
- Splenic cytokines (IL-2, IL-6, TNF) and natural killer (NK) cell activity were measured.
- The effects of the mu opioid receptor antagonist naloxone were assessed.
Main Results:
- Morphine suppressed NK cell activity and enhanced T-lymphocyte proliferation and IL-2/TNF-beta production.
- IL-6 and TNF-alpha production by splenic macrophages remained unaffected.
- Naloxone blocked morphine's effects, indicating mediation via mu opioid receptors.
Conclusions:
- Morphine exerts differential effects on various immune cells through opioid receptors in the PAG.
- These findings highlight the PAG as a key site for opioid-induced neuroimmunomodulation.