Protective effects of propranolol on experimentally head-injured mouse brains

Catecholamines have a deleterious effect on the traumatized brain. Propranolol, a beta-adrenergic blocker, can act on the vasomotor centers within the hypothalamus and brain stem to reduce the activity of the sympathetic nerves and the cerebral metabolic need for oxygen and glucose. This study investigated the effects of racemic (d,l) propranolol on the neurologic recovery of mice with head-injuries. Male BALB-C mice (n = 110) received a 1,100 g-cm head injury from a 50 g weight dropped from a height of 22 cm resulting in immediate loss of consciousness in all animals and some deaths. The survivors were divided into treatment (n = 46) and placebo (n = 45) groups. The treatment group received an intraperitoneal injection of propranolol 2.5mg/kg immediately after the head injury. The placebo group received the same amount of 0.9% normal saline by injection in the same time interval. Neurologic status was evaluated 1 hour after injury. A group of 50 mice without head injury was also tested to evaluate the performance of normal mice. All three groups of mice were then decapitated. Mice with depressed fractures of the skull (n = 1) or intracranial hematomas (n = 1) after head injury were excluded from the study. Small pieces of brain parenchyma were used to check the water content by gravimetric method. The treatment group showed better neurologic recovery than the placebo group by both the string test scoring system and grip test time. The brain edema was significantly reduced at the temporal lobes in the treatment group as compared to the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)