[A novel model of perfused rat brain with intact nervous system]

To obtain a model system, useful in brain research, we have developed a new perfused brain model in rats. In this model the cerebral circulation is separated from the systemic circulation, while the connection between the central and peripheral nervous system is preserved. After the external carotid and vertebral arteries were ligated, bilateral common carotid arteries and external jugular veins were cannulated. Rinsed human O-typed red blood cells and modified Ringer's solution were injected using two infusion pumps, and the venous blood was drained. The infusion rate was adjusted to achieve normal cerebral blood flow (CBF) of rats (the control state). Normal electrocortical activities were observed on electroencephalograms (EEGs) for more than 1 hour in the control state. Somatosensory evoked potentials were also recorded. Infusion of pentylenetetrazol (PTZ) induced epileptic discharges on the EEG and caused an increase in blood pressure. Measurements of cerebral oxygenation with near-infrared spectroscopy (NIRS) showed increase in total and oxygenated hemoglobin accompanied by a decrease in deoxygenated hemoglobin. Since the flow rate was not changed, the changes in the NIRS parameters may have reflected dilatation of arterioles. Using this new model, we can change CBF and/or cerebral metabolism without affecting the systemic circulation. Unlike previous isolated perfused brain models, the present model maintains the connection between the central and peripheral nervous system. Thus, our model should provide a new approach to brain research.