The brain-immune axis: role of opiates and other substances of abuse, the hypothalamic-pituitary-adrenal axis and behavior.

The brain-immune axis is a highly complex and dynamic homeostatic mechanism. The effect of morphine, or other drugs of abuse, on this interactive system can have multiple consequences, depending on the specific site(s) of action, duration of exposure and underlying neuroendocrine, neural and behavioral status. This emphasizes the critical role of interdisciplinary studies, incorporating behavioral, pharmacological, neuroanatomical, cellular and molecular approaches, that are necessary for elucidating opiate-BIA interactions. To characterize fundamental mechanisms of action, the sheer complexity of this system often requires that more rigorous experimental methodology be applied by multidisciplinary groups of investigators than ever before.