Localization of the spinal respiratory rhythm generator by an in vitro electrophysiological approach

An in vitro electrophysiological approach allowed the localization of the spinal respiratory generator (sRG) within the cervical cord of newborn rats. Rostral and caudal limits were determined through transections of the successive spinal segments. The sRG is mainly located in the C5 segment with a partial extension in the C4 and C6 segments. The presence of two lateralized sRG was found after a split of the brain stem cervical cord from T8 to C1. Spinal respiratory activity could be kept synchronous after this split in the right and left halves of the spinal cord. This spinal activity also displayed a bilateral synchrony on separated spinal cord preparations after a C1 transection with no split. These findings are the first attempt to localize the sRG and are discussed in terms of bilateral segmental coupling and of interactions between the medullary and the spinal respiratory generators.