Projections from the caudal part to the rostral part of the lateral septal area mediate blood pressure increase.

We previously demonstrated that restraint stress-induced pressor responses were inhibited by bilateral microinjection of muscimol into the rostral part of the ventral zone of the lateral septal area (LSV). The caudal part of the lateral septal area is also reported to be involved in blood pressure regulation. In this study, we examined whether the LSV receives projections from the caudal part of the dorsal zone of the lateral septal area (LSD) in rats. Injections of a fluorescent tracer into the LSV produced maximal retrograde labeling within the LSD. Microinjection of carbachol (10-100 pmol) into the LSD produced a dose-dependent pressor response. The pressor response to carbachol was inhibited by microinjection of muscimol (80 pmol) or 4-DAMP (1 nmol) into the ipsilateral side of the LSV. Microinjection of muscimol (80 pmol) into the LSD also inhibited the pressor response induced by restraint stress. Repeated injections of carbachol (30 pmol) into the LSD produced Fos immunoreactivity in the ipsilateral side of the LSV. These findings suggest that the LSD projects to the LSV and that these projections may be involved in blood pressure increase.