Median preoptic neurones are sensitive to blood pressure changes induced by peripheral angiotensin II

The activity of 50 histologically identified neurones of the median preoptic area (MPO) was recorded simultaneously with blood pressure monitoring. The responsiveness of these neurones was investigated with increasing doses (25-100 ng/ml/kg) of intravenously applied angiotensin II (ANG II). Mean blood pressure rose in a dose-dependent manner (between 3.9 +/- 0.5 and 18.6 +/- 2.6 mm Hg) whereas the rise in firing frequency of MPO neurones (between 47 and 105% of spontaneous discharge) was not dose-related. The latency of neuronal response decreased according to the dose applied: at the lowest dose of angiotensin it was longer (105 +/- 20 s) than at the highest dose (26 +/- 8 s). These findings suggest that MPO neurones are sensitive to ANG II-haemodynamic changes.