Atrial natriuretic factor in specific brain areas of spontaneously hypertensive rats

Atrial natriuretic peptides (atrial natriuretic factor, ANF) are present in a great number of brain areas inside and outside of the blood-brain barrier. The pattern of distribution implies the involvement of ANF in different physiological functions, such as blood pressure regulation, electrolyte and fluid homeostasis, and modulation of the neuroendocrine system. To further investigate a possible involvement of central ANF in spontaneous hypertension, we measured levels of ANF in 18 selected, microdissected brain areas of prehypertensive (4-week-old) and hypertensive (12-week-old) spontaneously hypertensive rats (SHR) and their normotensive control, Wistar-Kyoto rats (WKY), by radio-immunoassay. ANF was significantly decreased in seven brain areas in SHR at both ages investigated; the most pronounced decreases were found in the subfornical organ, in the perifornical and periventricular hypothalamic nuclei, and in the medial preoptic nucleus. In addition, in young SHR ANF was significantly decreased in the organum vasculosum laminae terminalis and increased in the median eminence. After the development of hypertension, a significant decrease of ANF could be detected in four more brain areas (bed nucleus of the stria terminalis, paraventricular and arcuate nuclei, dorsal raphe nucleus) of SHR, as compared with normotensive controls, and the increase in the median eminence was no longer detectable. These results suggest a role for ANF in genetic hypertension and the specific importance of certain brain regions.