The Effects of Dietary Salt on Blood Pressure Variability, Cerebral Perfusion and Cognitive Function in Young-Adult Male Rats

Abstract

Background: There is controversy about the relationship between dietary salt intake and cognitive function. Experimental studies showed that extremely high salt diets increased blood pressure (BP) levels, leading to cognitive impairment. However, extremely high salt diets are not clinically relevant. The present study examined how high dietary salt could affect cognitive function and whether these effects are via BP stability and cerebral hypoperfusion. Methods: SD rats (male, young adult) were on the control diet (0.4% NaCl), low salt diet (0.1% NaCl), or high salt diets (with three does at 1%, 2%, or 4% NaCl) for 12 weeks. BP levels, heart rate (HR), and BP variability (SD and CV) were measured repeatedly at baseline, 1, 2, 3, 4, 6, 8, and 12 weeks after the onset of the diet. Anxiety and cognitive function (open field, novel object recognition, and T-maze) were measured repeatedly at baseline, 4, 8, and 12 weeks after the onset of the diet. Blood Na+ and cerebral blood flow (CBF) were measured at the endpoint. Results: Rats with the low salt diet showed significantly reduced systolic BP (SBP) and diastolic BP (DBP) levels compared to those with the control diet and high salt diets at 8 weeks after the onset of the diet. Notably, rats with the low salt diet had the highest SBP variability (SBPV) and DBPV, while those with the control diet showed the lowest SBPV and DBPV. In high salt diet groups, SBPV and DBPV increased in a dose-dependent manner. There is no significant difference in HR between groups. Rats only with a 4% NaCl diet showed worse cognitive function compared to rats with low salt and control diet 8 weeks after the onset. Blood Na+ was similar between groups. Interestingly, the high salt diet increased the CBF in a dose-dependent manner. The CBF of the low salt diet was similar to those with 2% salt die, and the CBF of the control group was the lowest. Conclusions: This study suggests that a moderate-high salt diet would not affect cognitive function in young-adult male SD rats. Only consumption of an extremely high salt diet impaired cognitive function, and this harmful effect was not via cerebral hypoperfusion. Moreover, both low and high salt diets increased BPV. This research was funded by the START-UP FUNDING OF HANGZHOU NORMAL UNIVERSITY, grant number 4255C50221204123 (Dr. Fen Sun). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.