The impact of blood pressure on hippocampal glutamate and mnestic function

Abstract

Hypertension is associated with an increased risk of cognitive decline, which is generally regarded as a consequence of advanced cerebral atherosclerosis. Many hypertensive patients, however, suffer from cognitive decline long before they have any signs of cerebrovascular disease. Therefore, this study examines direct effects of blood pressure on neurotransmitter status in the hippocampus, a vulnerable cerebral structure relevant for memory consolidation. Absolute glutamate concentration and N-acetylaspartate (NAA) concentration as an alternative marker of neuronal integrity were determined in the hippocampus and the cerebral cortex (anterior cingulate cortex; ACC) by 3-T proton magnetic resonance spectroscopy in 16 probands without any history of cerebrovascular disease. Memory function was tested by the auditory verbal learning test (AVLT) and the rivermead behavioural memory test (RBMT). Arterial stiffness was assessed by augmentation index (AI). Mean arterial pressure showed a significant negative age-adjusted correlation to absolute glutamate concentrations in the hippocampus (R ¼ À0.655, P ¼ 0.011), but not in the ACC. There was no significant correlation of mean arterial pressure and NAA in either hippocampus or ACC. AI did not affect hippocampal glutamate. Moreover, there was a significant negative correlation between mean arterial pressure and AVLT (r ¼ À0.558, P ¼ 0.025) and RBMT score (r ¼ À0.555, P ¼ 0.026). There is an inverse relation between blood pressure and the concentration of hippocampal glutamate. Glutamate is essential for long-term potentiation, the neurobiological correlate for memory formation in the hippocampus. Thus, hypertension-associated cognitive decline may not only be mediated by structural atherosclerotic wall changes, but also by functional changes in neurotransmission.

Associations of Pulse and Blood Pressure with Hippocampal Volume by APOE and Cognitive Phenotype: The Alzheimer’s Disease Neuroimaging Initiative (ADNI)

“…As in previous reports of a nonlinear (U-shaped) relationship of blood pressure to cognitive performance in older adults [53], a U-shaped relationship of SBP and DBP to hippocampal volume was also evident in our analyses. These findings are congruent with reports of inverse relationships of blood pressure to concentrations of hippocampal glutamate (a crucial prerequisite of memory formation) [54] and to AD diagnosis years after blood pressure became elevated [55]. However, our study is unique in that it has the advantage of a large sample size, longitudinal follow-up, and stratification into cognitive and APOE genotype categories.…”

In vivo glutamate measured with magnetic resonance spectroscopy: behavioral correlates in aging

“…Higher systolic blood pressure was associated with lower striatal gray matter volume and striatal Glu. A similar inverse relationship was recently demonstrated between mean arterial pressure and hippocampal Glu levels [135]. Lenticulostriate arteries supply the head of the caudate nucleus, anterior internal capsule, and putamen [63], which are all regions included in the striatal voxel.…”

Preimplantation or gestation/lactation high-fat diet alters adult offspring metabolism and neurogenesis

“…Similarly, it has been described that blood pressure affects not only hippocampal glutamate status but also memory function by affecting hippocampal integrity. 65 Here we have seen that leptin receptors in the hippocampus are upregulated, and although we did not assess leptin in this study, it could be suggested that leptin might be related to elevated SBP in offspring.…”