The site of the origin of the so-called fastigial pressor response.

The cerebellar nuclei and subnuclear areas of anesthetized cats were electrically stimulated with glass microelectrodes to explore the origin of the so-called fastigial pressor response (FPR). The FPR was not derived from the fastigial nucleus per se, but from the subfastigial fiber bundle projecting into the pontine lateral parabrachial nucleus (Pbl). The microinjection of kainic acid did not facilitate the pressor response from the subfastigial fiber bundle, but facilitated the pressor response from the Pbl. When WGA-HRP was deposited in the pressor response site of the Pbl, labeling was found in axons of the subfastigial fiber bundle and in the fiber terminals and cells of the contralateral Pbl. This suggests that the FPR originates in the pressor response site in the Pbl which projects into the contralateral Pbl via the subfastigial fiber bundle.