Neurons in the nucleus of the solitary tract with ascending projections to the subfornical organ in the rat.

Thirty-one neurons in the region of the nucleus of the solitary tract (NTS) were antidromically activated by electrical stimulation of the subfornical organ (SFO) 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, 17 displayed an increase and 6 exhibited a reduction in neuronal firing that accompanied a 40- to 60-mmHg elevation in mean arterial pressure, while 8 were unresponsive. The results suggest that neurons projecting to the SFO in the region of the NTS may be important for carrying peripheral baroreceptor information to the SFO.