Natural Killer Cell Activity In Rats Research Articles

The role of opioids in cancer progression.

The role of opioids in cancer progression.

Tolerance development to morphine-induced alterations of immune status

A variety of in vitro immune measures were examined in groups of Lewis rats that chronically consumed either tap water or a 0.2, 0.4, or 0.6 mg/ml morphine drinking solution. Rats received a subcutaneous injection of either saline or 15 mg/kg morphine sulfate 1 h before sacrifice. In the water drinking groups, the acute morphine injection significantly suppressed splenic natural killer (NK) cell activity, mitogen-stimulated splenic T- and B-cell proliferation and γ-interferon (γ-IFN) production. A single, acute injection of morphine did not suppress NK cell activity in rats that drank the two highest concentrations of morphine, whereas it did suppress the mitogen-stimulated splenic T- and B-cell proliferation and γ-IFN production. These results suggest that rats that drank morphine for 20 days developed tolerance to morphine's suppressive effect on NK cell activity but not to other measures of immune status. Morphine drinking rats also developed tolerance to morphine's antinociceptive effects and revealed signs of physical dependence when the morphine solution was withdrawn or when naltrexone was administered.

Inhibitory effect of pregnancy on stress-induced immunosuppression through corticotropin releasing hormone (CRH) and dopaminergic systems

To clarify the involvement of pregnancy in the response of the neuroendocrine–immune system to stress, we examined splenic natural killer cell activity (NKCA) and its relevant central and blood parameters in female virgin and pregnant rats (10 to 11 days gestation) exposed to forced water-immersion stress with durations of 90 min and 180 min. Decreases in splenic NKCA, corticotropin releasing hormone (CRH) in the hypothalamus, and increases in progesterone (P), β-endorphin ( β EP), and dopamine (DA) metabolic ratios in the frontal cortex and nucleus accumbens produced by stress were recognized in the virgin rats, but not in the pregnant rats. Pregnancy reduced splenic NKCA in rats without stress, but elevated it in the rats exposed to stress with a duration of 180 min. These findings suggest inhibitory effects of pregnancy on stress-induced immunosuppression and neuroendocrine changes, thereby promoting homeostasis in the neuroendocrine–immune system against stress. Such enhanced homeostasis associated with pregnancy seemed to be mediated by the activation of placental P and placental or pituitary β EP in cooperation with mesocortical and mesolimbic DA systems and hypothalamic CRH.

Suppression of splenic natural killer cell activity in rats with brain tumors.

After inoculating 9L glioma cells into the brains or into subcutaneous regions of the back of rats, we investigated splenic natural killer (NK) cell activity for 3 weeks using a 4-hour 51Cr release assay. Only rats with brain tumors showed decreased splenic NK cell activity. The spleens of these rats were morphologically small and atrophic. Expansive brain tumors were compressing the basal ganglia, thalamus, and hypothalamus after 2 weeks, and the rats ultimately died of cerebral herniation, usually by 3 weeks after inoculation. The decreased splenic NK cell activity in rats with brain tumors might be the result of neuroimmunomodulation secondary to hypothalamic dysfunction due to increasing tumor compression.