Endogenous opioids, opiate receptors and traumatic brain injury.

The present study examined the role of endogenous opioid peptides in the pathophysiological sequelae of fluid percussion head injury in the cat. Two hours following injury, tissue concentrations of dynorphin-like immunoreactive material (ir-Dyn) were significantly elevated in specific brain regions where injury, as evidenced by histological examination, was most severe. Changes in ir-Dyn but not beta-endorphin-like immunoreactive material (ir-End) were significantly correlated with a fall in regional cerebral blood flow (CBF) that occurred 2 h following injury. Administration of the opiate antagonist WIN44,441-3 (with enhanced activity at kappa-receptors) stereospecifically increased cerebral blood flow to the injured regions.