ADRENALECTOMY INCREASES LOCAL CEREBRAL BLOOD-FLOW IN THE RAT HIPPOCAMPUS

The present study examined the effect of glucocorticoid manipulations on local cerebral blood flow in the hippocampus. We measured local cer ebral blood flow in the hippocampus at 1-h intervals over a 1-day peri od in freely moving rats, by means of the H-2 clearance method, before and after sham adrenalectomy, adrenalectomy or adrenalectomy with cor ticosterone replacement. We also measured local cerebral blood flow in the prefrontal cortex before and after adrenalectomy. Four weeks afte r the adrenalectomy, hippocampal blood flow at each time of day was an average of 47% greater than before the operation, showing diurnal var iation as before. After the sham adrenalectomy or adrenalectomy with c orticosterone replacement, hippocampal blood flow did not change signi ficantly with respect to either its level or its diurnal variation. Lo cal cerebral blood flow in the prefrontal cortex increased by only 19% after adrenalectomy. The present study demonstrates that adrenalectom y causes a remarkable increase in hippocampal blood flow, probably due to a lack of corticosterone.