Changes in brain monoamines and their metabolites during and after hemorrhagic shock in the rat

The alteration of monoamines and their metabolites in the brain during and after hemorrhagic shock in the conscious state was measured in rats. Blood pressure was maintained at 40-70 mmHg (5.3-9.3 kPa) for 60 min by withdrawing 8 ml of blood intermittently. The content of monoamines, as well as their metabolites, increased in various brain regions during hemorrhage, compared with the content in the control rats. Sixty min after the end of the bleeding period, almost no significant change in the contents of brain monoamines nor of their metabolites was observed. These results may indicate not only an increased release of monoamines from nerve terminals, but also an increased synthesis of them during hemorrhagic shock. Soon after the bleeding was stopped, the increased monoamine turnover rate returned to almost normal levels.