AREA POSTREMA IS ESSENTIAL FOR THE MAINTENANCE OF NORMAL BLOOD-PRESSURE UNDER COLD STRESS IN RATS

No final conclusion has yet been achieved on whether the area postrema (AP) is involved in the regulation of cardiovascular activity in the rats. The aim of the present study was to investigate the role of the AP in the regulation of basal blood pressure under normal as well as a bnormal (cold stress) conditions in Sprague-Dawley rats. The lesion of AP was performed by the electrolytic-lesion method. Stressed animals were subjected to chronic intermittent cold stress (2 degrees C, 3 h/d ay for 14 days). The systolic blood pressure was measured by the indir ect tail-cuff transducer method. The results showed that no significan t difference was found between systolic blood pressure measured before and after AP-lesion surgery. The AP-lesion group had similar systolic blood pressure to both sham-operation and the control groups under no rmal environmental conditions. However, it was found that cold stress resulted in a significant increase in systolic blood pressure in the A P-lesion rats, but not in sham-lesion animals, within two weeks. Furth ermore, there was no significant difference between blood pressures of sham-lesion rats with or without cold stress and the control animals. These results support the view that the AP plays no role in keeping b asal blood pressure under normal condition and indicate as well that t he AP is important in maintaining normal blood pressure under the cond itions of stress (cold).