Chronic exposure to morphine attenuates expression of interleukin-1 beta in the rat hippocampus

The cytokine, interleukin-1 beta (IL-1 beta), can modulate both immune and neuroendocrine events. Alteration of IL-1 beta expression by exogenous factors, such as morphine, may affect the neuro-endocrine-immune axis. Brain sections from male rats implanted with either morphine or placebo pellets were stained for IL-1 beta immunoreactivity. The results showed pronounced attenuation of IL-1 beta immuno-reactivity in the dentate gyrus and the CA1-CA3 fields of the hippocampus in morphine-implanted rats compared to placebo controls. It has been suggested that the hippocampus is involved in the regulation of hypothalamic activity. Attenuation of IL-1 beta expression in the hippocampus by chronic exposure to morphine may be one of the mechanisms underlying the neuro-endocrine-immune modulatory effects of opiate addiction.