Decrease of substance P in the parabrachial nucleus of multiple system atrophy.

In the parabrachial nucleus (PBN), which has been known to play an important regulating role for various autonomic functions, many projecting nerve fiber terminals containing substance P (SP) from the nucleus of the solitary tract (NTS) and other areas are found and effect a modulatory influence on the transmission in the PBN. Postmortem brains were obtained from four multiple system atrophy (MSA) patients with autonomic failure and four control patients without any nervous disease, and an immunohistochemical staining for SP was performed on serial 10-microm-thick sections from paraffin-embedded pons including the PBN after immersion fixation in 10% formalin. In the PBN of all MSA patients, a marked decrease in SP-like immunoreactive (SPLI) nerve fiber terminals was revealed compared with the controls. In addition, an obvious astrocytosis was found in the PBN by simultaneous histopathological evaluation, for the preservation of neurons themselves. Therefore, the projecting SP pathway to the PBN may also be primarily involved in the pathophysiological mechanism of the autonomic failure of MSA patients.