Modulation of intrathecal morphine-induced immunosuppression by microinjection of naloxone into periaqueductal gray.
OBJECTIVE
To study the involvement of opioid receptor of periaqueductal gray (PAG) and hypothalamic-pituitary-adrenal (HPA) axis in the effect of intrathecal morphine on immune function.


METHODS
Rat splenic natural killer (NK) cell activity was determined by a europium release assay; the concanavalin A-induced splenic IL-2 production, TNF-beta activity, and serum TNF-alpha level were determined by colorimetric thiazolyl blue tetrazolium bromide (MTT) and gentian violet assay, and serum corticotrophin (ACTH) level by radio-immunological method after intrathecal injection of morphine and PAG microinjection of naloxone.


RESULTS
Intrathecal morphine inhibited splenic NK cell activity, IL-2 production, TNF-beta activity, and increased in serum ACTH level. Microinjection of naloxone 1 microgram into PAG partially antagonized the inhibition of NK cell activity and the elevation of serum ACTH level by morphine.


CONCLUSIONS
The opioid receptor of PAG involved in the suppression of NK cell activity by intrathecal morphine, which was accompanied by an activation of HPA axis.
Zhang
Y
Y
State Key Laboratory of Medical Neurobiology, Shanghai Medical University, China.
Du
L N
LN
Wu
G C
GC
Cao
X D
XD
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D007278:Injections, Spinal; D007376:Interleukin-2 / Q000096:biosynthesis; D007694:Killer Cells, Natural / Q000276:immunology*; D008233:Lymphotoxin-alpha / Q000378:metabolism; D008297:Male; D008845:Microinjections; D009020:Morphine / Q000037:antagonists & inhibitors*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D010487:Periaqueductal Gray / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011957:Receptors, Opioid / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D007376:Interleukin-2; D008233:Lymphotoxin-alpha; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D014409:Tumor Necrosis Factor-alpha; D009270:Naloxone; D009020:Morphine; D000324:Adrenocorticotropic Hormone