Effect of Concussive Head Injury on Central Catecholamine Levels and Synthesis Rates in Rat Brain Regions 1

Abstract —Unanesthetized male Sprague‐Dawley rats were subjected to head injury using a unique acceleration‐deceleration model designed to mimic the most prevalent form of clinical head injury. Endogenous tyrosine, dopamine and norepinephrine were determined fluorometrically and catecholamine synthesis rates were determined by a radioisotopic method. These values were determined in four brain regions: cortex‐striatum, midbrain‐hypothalamus, medulla‐pons, and cerebellum, and were performed at 5 min, 15 min, 1 h, and 2h post‐trauma. Dopamine levels were elevated in the medulla pons region at 5 min after trauma and in the midbrain‐hypothalamus at the 15 min and 1 h time periods. This increase in dopamine levels may reflect disruption of dopamine beta hydroxylase activity. Norepinephrine synthesis rate in the cerebellum was elevated at 2 h after trauma. Changes in the other parameters were observed but appeared to be related to stress, and the effect of stress in this model is discussed.