Transport of CRH from mouse brain directly affects peripheral production of beta-endorphin by the spleen.

The blood-brain barrier (BBB) regulates the passage of substances between the brain and the periphery. It has not been shown that the secretion from the brain of a small amount of a substance can directly affect the periphery by transport across the BBB. We found that central injection of radioactively labeled corticotropin-releasing hormone (CRH) resulted in the accumulation of intact CRH in the spleen. CRH also increased splenic beta-endorphin, an effect not blocked by pretreatment with dexamethasone. Inhibition of the secretion of CRH from the brain by colchicine resulted in decreased accumulation of CRH in the spleen and also decreased splenic beta-endorphin. Similar findings occurred in the pituitary gland. The results show that the passage of labeled CRH from the brain can directly affect a peripheral organ, thus emphasizing the regulatory function of the BBB.