Early changes of immunoreactivity to Orexin in hypothalamus and to RFamide peptides in brainstem during the development of hypertension

Baroreflex sensitivity (BRS) is an important function of the nervous system and essential for maintaining blood pressure levels in the physiological range. In hypertension, BRS is decreased both in man and animals. Although increased sympathetic activity is thought to be the main cause of decreased BRS, hence the development of hypertension, the BRS is regulated by both sympathetic (SNS) and parasympathetic (PNS) nervous system. Here, we analyzed neuropeptide changes in the lateral hypothalamus (LH), which favours the SNS activity, as well as in PNS nuclei in the brainstem of spontaneously hypertensive rats (SHR) and their normotensive controls (Wistar Kyoto rats- WKY). The analyses revealed that in the WKY rats the hypothalamic orexin system, known for its role in sympathetic activation, showed a substantial decrease when animals age. At the same time, however, such a decrease was not observed when hypertension developed in the SHR. In contrast, Neuropeptide FF (NPFF) and Prolactin Releasing Peptide (PrRP) expression in the PNS associated Nucleus Tractus Solitarius (NTS) and Dorsal Motor Nucleus of the Vagus (DMV) diminished substantially, not only after the establishment of hypertension but also before its onset. Therefore, the current results indicate early changes in areas of the central nervous system involved in SNS and PNS control of blood pressure and associated with the development of hypertension.