ALTERATION OF OPIOID PEPTIDE CONCENTRATIONS IN THE RAT PITUITARY FOLLOWING SURVIVABLE CLOSED-HEAD INJURY

Concentration changes of methionine enkephalin-like immunoreactivity ( ME-li) and beta-endorphin-like immunoreactivity (BE-li) in the rat pit uitary following diffuse brain injury were studied. Closed head injury was induced by a weight-drop trauma device (450 g X 2 m). The level o f closed head injury used in this study altered the pituitary opioid p eptide concentrations. The level of ME-li did not change in the experi mental groups 3 hours, 10 hours, 24 hours, and 3 days after the trauma , but significantly increased by 34% 10 days after the trauma. BE-li r emained constant 3 hours and 10 hours following the injury, increased by 48% at 24 hours, and remained at this level for 10 days after the t rauma (44% at 3 days, and 40% at 10 days). The levels of ME-li and BE- li in the control sham-operated rats did not change during these times . The present measurements of BE-li and ME-li in the pituitary indicat e that the opioid peptides that derive from two different neuropeptide rgic systems, proopiomelanocortin (POMC) and preproenkephalin A, respe ctively, may participate in the pathophysiology of a closed head injur y.