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.

A single day of constant light (L/L) provides immunity to behavioral despair in female rats maintained on an L/D cycle.

The present experiment investigated the potentially ameliorative effect of exposure to light in the dark phase of an 12:12 h daily lighting schedule (12L/12D cycle) on behavioral despair, an animal model of depression based on two forced swim tests separated by 24 h. Experimental groups of female Wistar rats were maintained on the 12L/12D cycle except for a single exposure to 12 h of light treatment in the dark phase of the 12L/12D cycle. Control animals were treated similarly except for light treatment. Animals then underwent one of two sets of behavioral tests starting on either the day light (or control) treatment ended (No Delay groups) or 24 h thereafter (Delay groups). The treatment for subgroups of light-treated and control animals tested with or without delay consisted of either two forced swim tests separated by 24 h or testing in the open field and elevated plus maze. Results indicated that a single exposure to a 12-h light treatment has protective effect on behavioral despair in groups tested with or without delay as measured by shorter duration of immobility in the second swim test compared to the controls. Light-treated and control animals behaved similarly in the open field and elevated plus-maze tests.