Circulatory and respiratory responses to glutamate stimulation of the lateral parabrachial nucleus of the cat.

Electrical stimulation of the dorsal part of the lateral parabrachial nucleus (Pbl) induced a pressor response associated with a brief hyperpneic response, whereas glutamate stimulation induced no response, suggesting that the response to electrical stimulation may be due to excitation of passing fibers. Electrical stimulation of the lateral part of the Pbl induced a pressor and hyperpneic response, while glutamate stimulation induced either a pressor-depressor or single depressor response associated with a hyperpneic and polypneic response, suggesting that the response to electrical stimulation of the lateral part may be due to excitation of cell bodies. WGA-HRP study clarified that the cells in the region around the ventrolateral edge of the brachium conjunctivum project to the cells in the C1 area and subfacial cell group of the rostral ventrolateral medulla (RVLM), suggesting that the cells in this region may send a message to the sympathetic premotor and respiratory premotor cells in the RVLM. Inversely, the cells in the C1 area and the subfacial cell group project to the lateral part of the Pbl, suggesting mutual innervation between the Pbl and RVLM.