LOCALIZATION OF THE CENTRAL CARDIOVASCULAR SUBSTANCE-P REACTION

In conscious rats, intracerebroventricular (i.c.v.) substance-P (SP) induces the typical cardiovascular defense reaction. The aim of this study was to localize the central cardiovascular actions of SP. Two different methods were used: 1. Microinjections of SP into the specific brain areas: medial preoptic area (MPO), anterior hypothalamus (AH) and ventral tegmental area (VTA). 2. Injections of special cream (eucerine cum aqua) to cover the periventricular structures in the third ventricle (rostral plug) or to obstruct the aquaeductus cerebri (caudal plug). Thus, i.c.v. SP could not act on periventricular structures in the third ventricle or reach lower brain stem areas. Microinjections of SP into the MPO and AH, but not into the VTA, were able to elicit the typical cardiovascular defense reaction. The cardiovascular responses to i.c.v. SP were attenuated in rostral plug as well as in caudal plug groups of animals, compared to controls. Our data suggest that the MPO and AH are important brain areas for the generation of the SP-induced cardiovascular defense reaction. Moreover, the functional integrity of periventricular structures and lower brain stem areas appears to be important for this response.