Median preoptic neurons projecting to the hypothalamic paraventricular nucleus are sensitive to blood pressure changes.

Twenty-one neurons in the median preoptic nucleus (MnPO) were antidromically activated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN) in male rats under urethane anesthesia. The activity of these identified neurons was tested for a response to activation of peripheral baroreceptors, achieved by rising arterial blood pressure with an intravenous administration of the alpha-agonist metaraminol. Of the neurons tested, 14 displayed a reduction and 2 exhibited an increase in neuronal excitability that accompanied a 30- to 50-mmHg elevation in mean arterial pressure, while 5 were unresponsive. The results show that efferent pathways from the MnPO to the PVN may receive neural inputs from the peripheral baroreceptors, suggesting the involvement of the pathways in the control of cardiovascular function.