Stimulation of the parabrachial nuclei with monosodium glutamate increases arterial pressure.

In the urethane-anesthetized rat both electrical stimulation (20 microA, 0.2 ms, 30 s) through micropipettes and glutamate injections (0.1 M, 100 nl) within an area including the dorsal lateral parabrachial nucleus, the adjacent central lateral parabrachial nucleus, the external lateral parabrachial nucleus, the Kölliker-Fuse nucleus, and the adjacent medial parabrachial nucleus led to increases in mean arterial pressure (electrical, 34.2 +/- 18.6 mm Hg; glutamate, 14.0 +/- 8.3 mm Hg). The magnitude of the glutamate responses appeared to be inversely related to the distance between the ventrolateral tip of the brachium conjunctivum and the site of injection. In contrast, electrical stimulation within an area between the caudal medial parabrachial nucleus and the locus coeruleus led to increases in mean arterial pressure (24.4 +/- 12.5 mm Hg), whereas glutamate injections within this area led to decreases in mean arterial pressure (-14.8 +/- 5.3 mm Hg).