Neuroendocrine-immune interactions and their relevance to the pharmacology of critical care medicine.

: Many clinical conditions and the drug used to treat them are characterized by derangements of the brain/endocrine/immune axis. Drugs commonly used in the ICU have previously unrecognized effects on the immune system; these drugs (including steroid hormones, dopamine agonists, metoclopramide, haloperidol, morphine, mucolytics, cyclosporine and other pharmacologic agents) affect the release of hormones that, in turn, modulate immune function. This article will summarize some important functional interactions among the brain and the endocrine and immune systems, with particular relevance to the practice of critical care medicine. Evidence will be presented to demonstrate that the immunosuppressive effects of hypoprolactinemia, chronic morphine treatment and chronic glucocorticoid administration are reversed by prolactin or by drugs that stimulate endogenous prolactin release. Furthermore, prolactin, synthesized by lymphocytes, plays an autocrine role in their proliferation.