Why does the spontaneously hypertensive rat have an exaggerated preference for sweet and salty solutions? An hypothesis

Taste solution consumption by FHH-Chr nBN consomic rats

There has been extensive work to elucidate the behavioral and physiological mechanisms responsible for taste preferences of the rat but little attempt to delineate the underlying genetic architecture. Here, we exploit the FHH-Chr n(BN)/Mcwi consomic rat strain set to identify chromosomes carrying genes responsible for taste preferences. We screened the parental Fawn Hooded Hypertensive (FHH) and Brown Norway (BN) strains and 22 FHH-Chr n(BN) consomic strains, with 96-h 2-bottle tests, involving a choice between water and each of the following 16 solutions: 10 mM NaCl, 237 mM NaCl, 32 mM CaCl(2), 1 mM saccharin, 100 mM NH(4)Cl, 32 mM sucrose, 100 mM KCl, 4% ethanol, 1 mM HCl, 10 mM monosodium glutamate, 1 mM citric acid, 32 microM quinine hydrochloride, 1% corn oil, 32 microM denatonium, 1% Polycose, and 1 microM capsaicin. Depending on the taste solution involved, between 1 and 16 chromosomes were implicated in the response. Few of these chromosomes carried genes believed to mediate taste transduction in the mouse, and many chromosomes with no candidate taste genes were revealed. The genetic architecture of taste preferences is considerably more complex than has heretofore been acknowledged.

Water deprivation-induced sodium appetite and differential expression of encephalic c-Fos immunoreactivity in the spontaneously hypertensive rat

The spontaneously hypertensive rat (SHR) has an intense consumption of NaCl solution. Water deprivation (WD) followed by water intake to satiety induces partial rehydration (PR)-the WD-PR protocol-and sodium appetite. In the present work, WD produced similar water intake and no alterations in arterial pressure among spontaneously hypertensive rat (SHR), Wistar-Kyoto, and Holtzman strains. It also increased the number of cells with positive c-Fos immunoreactivity (Fos-IR) in the lamina terminalis and in the hypothalamic supraoptic (SON) and paraventricular (parvocellular, PVNp) nucleus in these strains. The WD and WD-PR produced similar alterations in all strains in serum osmolality and protein, plasma renin activity, and sodium balance. The SHR ingested about 10 times more 0.3 M NaCl than normotensives strains in the sodium appetite test that follows WD-PR. After WD-PR, the Fos-IR persisted, elevated in the lamina terminalis of all strains but notably in the subfornical organ of the SHR. The WD-PR reversed Fos-IR in the SON of all strains and in the PVNp of SHR. It induced Fos-IR in the area postrema and in the nucleus of the solitary tract (NTS), dorsal raphe, parabrachial (PBN), pre-locus coeruleus (pre-LC), suprachiasmatic, and central amygdalar nucleus of all strains. This effect was bigger in the caudal-NTS, pre-LC, and medial-PBN of SHRs. The results indicate that WD-PR increases cell activity in the forebrain and hindbrain areas that control sodium appetite in the rat. They also suggest that increased cell activity in facilitatory brain areas precedes the intense 0.3 M NaCl intake of the SHR in the sodium appetite test.

ARTERIAL BAROREFLEX IS NOT INVOLVED IN SALT PREFERENCE IN RATS

1. One unusual and interesting feature of spontaneously hypertensive rats (SHR) is their salt preference. This behaviour is known to be independent of blood pressure. 2. Arterial baroreflex (ABR) function is impaired in SHR. Therefore, the present study was designed to explore the relationship between ABR function and salt preference in rats. 3. Twenty-seven SHR, aged 11 months, were used. Blood pressure and baroreflex sensitivity (BRS) were determined in conscious, freely moving SHR after the measurement of salt preference. It was found that BRS did not relate to the salt preference in these rats. 4. Another group of normotensive Sprague-Dawley rats, aged 10 weeks, underwent either sinoaortic denervation (SAD) or sham operation. Salt preference was determined before and 4 weeks after SAD. Sinoaortic denervation did not alter salt preference in normotensive rats. 5. It is concluded that ABR function does not influence the salt preference in rats.

Long-term intake of egg white hydrolysate attenuates the development of hypertension in spontaneously hypertensive rats

This paper evaluates the effect of the long-term intake of a hydrolysate of egg white with pepsin (HEW), with a potent angiotensin converting enzyme inhibitory activity, on the development of hypertension of spontaneously hypertensive rats (SHR). After being weaned, male 3-week-old SHR were randomly divided into five groups that were given until the 20th week of life the following drinking fluids: (1) tap water, (2) non-treated egg white 1 g/kg/day, (3) captopril 100 mg/kg/day, (4) HEW 0.5 g/kg/day, and (5) HEW 1 g/kg/day. From the 20th to 25th week of life, animals from all groups were given tap water. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured weekly in the rats, from the 6th to 25th week of life, by the tail cuff method. Development of hypertension was attenuated in the groups treated with captopril and HEW (P<0.001 vs. the group that drunk tap water). At the 20th week of life, the arterial blood pressure values of the different groups of rats were: tap water (SBP = 219.5 +/- 5.7, DBP = 167 +/- 3.7), non-treated egg white (SBP = 206.4 +/- 1.43, DBP = 166.4 +/- 4.9), captopril (SBP = 131.7 +/- 2.74, DBP = 91.5 +/- 1.62), HEW 0.5 g/kg/day (SBP = 182.9 +/- 4.64, DBP = 127.5 +/- 2.1) and HEW 1 g/kg/day (SBP = 177.7 +/- 4.72, DBP = 120.1 +/- 2.4). SBP and DBP increased in the treated SHR when the corresponding antihypertensive treatment was removed. In spite of this, SBP remained lower in the SHR that had received captopril and HEW than in the SHR of the control groups (P<0.05). The present results suggest that HEW could be used as a functional food with antihypertensive activity.