Cognitive function and antihypertensive treatment in the elderly: a 6-year follow-up study

Effects of Dihydropyridines on the Motor and Cognitive Outcomes of Patients with Parkinson's Disease

BACKGROUND

Dihydropyridines (DHPs) may have neuroprotective effects against Parkinson's disease (PD).

OBJECTIVE

This study investigated the effects of DHPs on nigrostriatal dopaminergic denervation and longitudinal motor and cognitive outcomes in PD.

METHODS

We classified 476 patients with drug-naive PD who had undergone dopamine transporter imaging into three groups. They were selected according to a prior diagnosis of hypertension and use of DHPs and were matched using propensity scores: patients without hypertension (HTN-; n = 50) and patients with hypertension treated without DHP (HTN+/DHP-; n = 50) or with DHP (HTN+/DHP+; n = 50). Multiple linear regression and linear mixed model analyses were performed to determine intergroup differences in baseline dopamine transporter availability and longitudinal changes in the levodopa-equivalent dose, respectively. Using Kaplan-Meier analyses, we compared the risks of levodopa-induced dyskinesia, wearing off, and dementia-free survival during the 5.06 years of the mean follow-up period. The Cox regression model determined the independent effects of DHPs on dementia conversion.

RESULTS

Dopamine transporter availability in all striatal subregions was comparable between the HTN-, HTN+/DHP-, and HTN+/DHP+ groups. The risks of levodopa-induced dyskinesia and wearing off, as well as longitudinal changes in the levodopa-equivalent dose, did not differ between the groups. The HTN+/DHP+ group had a lower risk of developing dementia than the HTN+/DHP- (Bonferroni-corrected P_log-rank  = 0.036) group. The use of DHP was independently associated with a lower risk of dementia conversion after controlling for other antihypertensive drugs and confounding factors (hazard ratio, 0.242; 95% confidence interval, 0.087-0.668; P = 0.006).

CONCLUSIONS

DHPs may be associated with better long-term cognitive outcomes in hypertensive patients with PD. © 2023 International Parkinson and Movement Disorder Society.

Cognitive impairment in patients with heart failure: molecular mechanism and therapy

Heart failure (HF) is associated with multiple organ dysfunction and many comorbidities. Its incidence is high among the elderly and is a major health burden worldwide. Cognitive impairment (CI) is highly prevalent in older patients with HF, which is an abnormality in one or more of the items of cognition, attention, memory, language, psychomotor function, and visual spatial acuity. Studies have shown that the incidence of CI in HF patients is between 13 and 54%, and patients with both conditions have poor self-care ability and prognosis, as well as increased mortality rates. However, the mechanisms of CI development in HF patients are still unclear. In this review, we describe the epidemiology and risk factors as well as measures of improving CI in HF patients. We update the latest pathophysiological mechanisms related to the neurocognitive changes in HF patients, expounding on the mechanisms associated with the development of CI in HF patients.

Selective Vulnerability of the Locus Coeruleus Noradrenergic System and its Role in Modulation of Neuroinflammation, Cognition, and Neurodegeneration

Locus coeruleus (LC) noradrenergic (NE) neurons supply the main adrenergic input to the forebrain. NE is a dual modulator of cognition and neuroinflammation. NE neurons of the LC are particularly vulnerable to degeneration both with normal aging and in neurodegenerative disorders. Consequences of this vulnerability can be observed in both cognitive impairment and dysregulation of neuroinflammation. LC NE neurons are pacemaker neurons that are active during waking and arousal and are responsive to stressors in the environment. Chronic overactivation is thought to be a major contributor to the vulnerability of these neurons. Here we review what is known about the mechanisms underlying this neuronal vulnerability and combinations of environmental and genetic factors that contribute to confer risk to these important brainstem neuromodulatory and immunomodulatory neurons. Finally, we discuss proposed and potential interventions that may reduce the overall risk for LC NE neuronal degeneration.

Targeting the Beta-2-Adrenergic Receptor and the Risk of Developing Alzheimer's Disease: A Retrospective Inception Cohort Study

Background:

Animal studies suggested that β2-Adrenergic receptors (β2AR) may be a potential target for the treatment of Alzheimer’s disease (AD).

Objective:

This retrospective inception cohort study aimed to assess the association between antagonists and agonists of the β2AR and the risk of starting treatment for AD in older adults.

Methods:

A retrospective inception cohort study was conducted among older adults who initiated either non-selective βAR antagonists or selective β2AR agonists using the University Groningen IADB.nl prescription database (study period 1994–2019). For each exposed cohort, two reference cohorts (A and B) were matched on age at index date. The main outcome was defined as at least two prescriptions for cholinesterase inhibitors (rivastigmine, galantamine, and donepezil) and/or memantine. Cox proportional hazard regression models were used to estimate hazard ratios (HR).

Results:

The risk of developing AD was elevated among patients exposed to non-selective βAR antagonists (A: aHR 3.303, 95% CI 1.230–8.869, B: aHR 1.569, 95% CI 0.560–4.394) and reduced among patients exposed to selective β2AR agonists (A: aHR 0.049, 95% CI 0.003–0.795, B: aHR 0.834, 95% CI 0.075–9.273) compared to reference patients.

Conclusion:

These findings suggest that exposure to non-selective βAR antagonists is associated with an increased risk for developing AD whereas there may be a decreased risk for developing AD after exposure to selective β2AR agonists.

A Timeline of Ca2+/cAMP Signalling: From Basic Research to Potential Therapeutics for Dementia

BACKGROUND

The hypothesis that a dyshomeostasis of Ca2+ increases the incidence of dementia has been established. Several discoveries have emphasized the concept that a decrease in the excess of Ca2+ could be an interesting pharmacological target to alleviate dementia symptoms. Aging along with a healthy brain can be supported by daily exercise, self-control in caloric ingestion, and participation in intellectually challenging events. These lifestyle factors may alleviate the excess of Ca2+ resulting from a Ca2+ dyshomeostasis. Curiously, epidemiological and clinical studies have also reported a clinical relationship between hypertension, diabetes, and other inflammatory processes, and a higher risk of cognition decline. Considering the cumulative data from the scientific literature, including data of high evidence such as meta-analysis and systematic reviews, we can now link a Ca2+ dyshomeostasis as an upstream factor for hypertension, diabetes and other inflammatory processes, and dementia. Several reports have also indicated that increasing cAMP levels may induce neuroprotective outcomes, thus alleviating dementia symptoms.

METHODS

With these concepts in mind, we found that the pharmacological manipulation of Ca2+/cAMP signalling could be a novel plausible target to treat dementia. This article puts together fundamental concepts and current therapies to treat dementia, including novel therapeutics coming from the pharmacological manipulation of Ca2+/cAMP signalling.

RESULTS

Then, combined with improvements in the lifestyle issues, these novel therapeutics may allow sustained improvements in the life quality of age-related neurological patients.

CONCLUSIONS

In addition, considering coronavirus disease 2019 (COVID-19) is a rapidly evolving field, this article also reviewed recent reports about Ca2+ channel blockers' role in restoring Ca2+ signalling disruption due to COVID-19. Finally, this article also presents a timeline of the major events in Ca2+/cAMP signaling.

Age-related neuroinflammation and pathology in the locus coeruleus and hippocampus: beta-adrenergic antagonists exacerbate impairment of learning and memory in aged mice

The locus coeruleus (LC) provides the primary noradrenergic input to the forebrain and hippocampus, and may be vulnerable to degeneration and contribute to age-related cognitive decline and neuroinflammation. Additionally, inhibition of noradrenergic transmission by brain-permeable beta-blockers could exacerbate cognitive impairment. This study examined effects of age and acute beta-blocker administration on LC and hippocampus pathology, neuroinflammation and learning and memory behavior in mice. Male mice, 3 and 18 months old, were administered propranolol (beta-blocker) or mabuterol (beta-adrenergic agonist) acutely around behavioral assessment. Terminal inflammatory markers in plasma, hippocampus and LC were assessed alongside histopathology. An increase in hippocampal and LC microgliosis and inflammatory proteins in the hippocampus was detected in aged mice. We report pathological hyperphosphorylation of the postsynaptic NMDA receptor subunit 2B (NR2B) in the hippocampus, suggesting neuronal hyperexcitability. Furthermore, the aged proteome revealed an induction in proteins related to energy metabolism, and mitochondria dysfunction in the LC and hippocampus. In a series of hippocampal dependent behavioral assessment tasks acute beta-adrenergic agonist or beta blocker administration altered learning and memory behavior in both aged and young mice. In Y-maze, propranolol and mabuterol differentially altered time spent in novel versus familiar arms in young and aged mice. Propranolol impaired Novel Object Recognition in both young and aged mice. Mabuterol enhanced trace learning in fear conditioning. Aged mice froze more to context and less to cue. Propranolol impaired contextual recall in aged mice. Concluding, aged mice show LC and hippocampus pathology and heightened effects of beta-adrenergic pharmacology on learning and memory.

Beta-adrenergic receptor antagonism is proinflammatory and exacerbates neuroinflammation in a mouse model of Alzheimer's Disease

Adrenergic systems regulate both cognitive function and immune function. The primary source of adrenergic signaling in the brain is norepinephrine (NE) neurons of the locus coeruleus (LC), which are vulnerable to age-related degeneration and are one of the earliest sites of pathology and degeneration in neurodegenerative disorders such as Alzheimer's Disease (AD). Loss of adrenergic tone may potentiate neuroinflammation both in aging and neurodegenerative conditions. Importantly, beta-blockers (beta-adrenergic antagonists) are a common treatment for hypertension, co-morbid with aging, and may further exacerbate neuroinflammation associated with loss of adrenergic tone in the central nervous system (CNS). The present studies were designed to both examine proinflammatory consequences of beta-blocker administration in an acute lipopolysaccharide (LPS) model as well as to examine chronic effects of beta-blocker administration on neuroinflammation and behavior in an amyloid-beta protein precursor (APP) mouse model of AD. We provide evidence for robust potentiation of peripheral inflammation with 4 different beta-blockers in an acute model of LPS. However, beta-blockers did not potentiate CNS inflammation in this model. Notably, in this same model, the genetic knockdown of either beta1- or beta2-adrenergic receptors in microglia did potentiate CNS inflammation. Furthermore, in an APP mouse model of amyloid pathology, chronic beta-blocker administration did potentiate CNS inflammation. The beta-blocker, metoprolol, also induced markers of phagocytosis and impaired cognitive behavior in both wild-type and APP mice. Given the induction of markers of phagocytosis in vivo, we examined phagocytosis of synaptosomes in an in vitro primary microglia culture and showed that beta-blockers enhanced whereas beta-adrenergic agonists inhibited phagocytosis of synaptosomes. In conclusion, beta-blockers potentiated inflammation peripherally in a systemic model of inflammation and centrally in an amyloidosis model of neuroinflammation. Additionally, beta-blockers impaired learning and memory and modulated synaptic phagocytosis with implications for synaptic degeneration. These findings warrant further consideration of the proinflammatory consequences of chronic beta-blocker administration, which are not restricted to the periphery in patients with neurodegenerative disorders.

Beta-Blockers for the Secondary Prevention of Myocardial Infarction in People with Dementia: A Systematic Review

Background:

Cardiovascular disease remains the most common cause of death in industrialized countries. The use of beta-blockers is well established as a secondary prevention of myocardial infarction. However, little is known about the benefits of beta-blockers for people living with dementia.

Objective:

To evaluate the use of beta-blockers in people with dementia who have had a myocardial infarction, in order to identify associations between medication use, mortality, re-infarction and functional decline.

Methods:

We searched for all studies (randomized trials, observational cohorts) reporting beta-blocker use in populations with both dementia and previous myocardial infarction. Relevant keywords were used in Medline, Embase, and Web of Science up to October 2018. Titles and abstracts were independently screened by two reviewers. Quality of eligible studies was assessed using the Newcastle-Ottawa Scale. PRISMA recommendations were followed throughout.

Results:

Two observational studies were included, representing 10,992 individuals in a community setting and 129,092 individuals from a hospital record-linkage study. One showed use of beta-blockers reduced all-cause mortality (HR 0.74 (95% CI 0.64– 0.86) alongside evidence for an increased rate of functional decline in individuals aged≥65 with moderate to severe cognitive impairment (OR 1.34 (95% CI 1.11– 1.61)). The second study did not find an association between beta-blocker use and mortality in the population living with dementia.

Conclusion:

There is insufficient evidence to support use of beta-blockers to persons living with dementia. A single study provides limited evidence that beta-blockers improve survival rates but with associated detrimental effects on functional status in nursing home residents with cognitive impairment. Decisions to continue beta-blockers in persons living with dementia should be made on an individual basis.

Relationship Between Antihypertensive Medications and Cognitive Impairment: Part I. Review of Human Studies and Clinical Trials

Purpose of review

There is an established association between hypertension and increased risk of poor cognitive performance and dementia including Alzheimer’s disease; however, associations between antihypertensive medications (AHMs) and dementia risk are less consistent. An increased interest in AHM has resulted in expanding publications; however, none of the recent reviews are comprehensive. Our extensive review includes 15 observational and randomized controlled trials (RCTs) published over the last 5 years, assessing the relationship between AHM and cognitive impairment.

Recent findings

All classes of AHM showed similar result patterns in human studies with the majority of study results reporting point estimates below one and only a small number of studies (N = 15) reporting statistically significant results in favor of a specific class.

Summary

Only a small number of studies reported statistically significant results in favor of a specific class of AHM. Methodological limitations of the studies prevent definitive conclusions. Further work is now needed to evaluate the class of AHM and cognitive outcomes in future RCTs, with a particular focus on the drugs with the promising results in both animals and human observational studies.

Electronic supplementary material

The online version of this article (doi:10.1007/s11906-016-0674-1) contains supplementary material, which is available to authorized users.

A 10-year follow-up study of the association between calcium channel blocker use and the risk of dementia in elderly hypertensive patients

Calcium channel blockers (CCBs) are widely used for reducing blood pressure of hypertensive patients. Recent reports document the beneficial effects of CCB for preventing dementia; however, the results are controversial. We aim to evaluate the risk of developing dementia among elderly hypertensive patients treated with CCB.We designed a retrospective population-based cohort study using the records of the National Health Insurance Research Database of Taiwan dated from 2000 to 2010. The study cohort comprised 82,107 hypertensive patients of more than 60 years of age, and 4004 propensity score (PS)-matched pairs were selected according to age, sex, year of hypertension diagnosis, and baseline comorbidities. We employed a robust Cox proportional hazard model to estimate the hazard ratio (HR) of developing dementia in the PS-matched cohort.The annual incidence of dementia in the CCB-exposure group was significantly lower than that in the comparator group (3.9 vs 6.9 per 1000 person-years, P < 0.01) during the follow-up period (4.4 ± 2.5 years). Based on the PS-matched cohort, the adjusted HR of dementia in the CCB-exposure group was significantly lower than that in comparator group (HR = 0.53, 95% confidence interval: 0.39-0.72, P < 0.01). Sensitivity and subgroup analyses also confirmed similar findings.Our results provided evidence for an association between CCB use and a lower risk of developing dementia among the elderly hypertensive patients. Further studies are required to explore the causal relationship between CCB use and dementia.

Antihypertensive drug use and risk of cognitive decline in the very old: an observational study - the Newcastle 85+ Study

OBJECTIVES

Older adults are a fast growing group in society and are at high risk of hypertension, cognitive decline and dementia. Antihypertensive drugs, particularly calcium channel blockers (CCB), have been associated with a decreased risk of cognitive decline and dementia. We used observational data to examine the association between antihypertensive drug class and change in cognitive function.

METHODS

The Newcastle 85+ Study is a population-based cohort study recruiting individuals aged 85 (born in 1921) via general/family practices in Newcastle/North Tyneside, United Kingdom. Data, including blood pressure, antihypertensive drug use and cognitive function [assessed using the Standardized Mini-Mental State Exam (SMMSE)], were collected at baseline and 3-year follow-up.

RESULTS

The study population comprised 238 participants with a diagnosis of hypertension, prescribed antihypertensive drug treatment and with baseline and follow-up SMMSE assessment. There was an association between CCB use and less cognitive decline over 3 years (rate of decline was lower by 1.29 SMMSE points (95% confidence interval 0.16-2.42; P = 0.03) compared with those taking other antihypertensive classes after adjustment for age, sex, years of education, baseline SMMSE score, smoking, BMI, baseline blood pressure, and incident cerebrovascular event. This finding was even stronger in the cognitively intact (SMMSE >24), wherein rate of cognitive decline was lower by 1.33 SMMSE points (95% confidence interval 0.30-2.37; P = 0.01), but was not seen for other antihypertensive classes.

CONCLUSION

Findings provide support for an association between CCB use and a lower rate of cognitive decline in very old adults with hypertension.

Can the Treatment of Hypertension in the Middle-Aged Prevent Dementia in the Elderly?

Hypertension, one of the main risk factors for cardiovascular disease, is thought to play a crucial role in the pathophysiology of cognitive impairment. Studies have associated hypertension with subjective cognitive failures and objective cognitive decline. Subjective cognitive failures may reflect the early phase of a long pathological process leading to cognitive decline and dementia that has been associated with hypertension and other cardiovascular risk factors. The underlying cerebral structural change associated with cognitive decline may be a consequence of the cerebral small-vessel disease induced by high blood pressure and may be detected on magnetic resonance imaging as white matter hyperintensities, cerebral microbleeds, lacunar infarcts or enlarged perivascular spaces. The increasing interest in the relationship between hypertension and cognitive decline is based on the fact that blood pressure control in middle-aged subjects may delay or stop the progression of cognitive decline and reduce the risk of dementia in the elderly. Although more evidence is required, several studies on hypertension have shown a beneficial effect on the incidence of dementia.

A systematic review of calcium channel blocker use and cognitive decline/dementia in the elderly

OBJECTIVE

Treating hypertension in those aged at least 80 years is now recommended; however, the best antihypertensive to choose remains unexplored. Calcium channel blocker (CCB) use has been associated with a decreased risk of incident dementia in a younger hypertensive group but with an increased risk of cognitive decline in the very elderly. Either result could have a large impact on a vulnerable population. The aim of this review was to assess the evidence relating CCB use to later cognitive decline or dementia in the very elderly.

METHODS

A systematic review of the literature was carried out. The databases Medline, PubMed, Embase and Psychinfo were searched from 1980 to 22 August 2013. Abstracts were reviewed by two independent reviewers and papers meeting the inclusion criteria were extracted.

RESULTS

One thousand, nine hundred and sixty-eight records were reviewed and 10 articles reporting on nine studies retained and extracted. Data were primarily from cohort studies. Only one reported a randomized controlled trial comparing CCBs with placebo. Populations, comparator groups, follow-up times, outcomes and exposure varied and overall results were mixed. It was not possible to combine all studies, but those reporting Alzheimer's disease outcomes were combined to produce an overall risk ratio of 0.79 (95% confidence interval 0.53-1.17).

CONCLUSION

At present, there is no clear evidence to suggest that CCB use increases or decreases risk of cognitive decline or dementia in the very elderly. A robust clinical trial is now required to resolve this.

The Locus Coeruleus: Essential for Maintaining Cognitive Function and the Aging Brain

Research on cognitive aging has focused on how decline in various cortical and hippocampal regions influence cognition. However, brainstem regions play essential modulatory roles, and new evidence suggests that, among these, the integrity of the locus coeruleus (LC)-norepinephrine (NE) system plays a key role in determining late-life cognitive abilities. The LC is especially vulnerable to toxins and infection and is often the first place Alzheimer's-related pathology appears, with most people showing at least some tau pathology by their mid-20s. On the other hand, NE released from the LC during arousing, mentally challenging, or novel situations helps to protect neurons from damage, which may help to explain how education and engaging careers prevent cognitive decline in later years.

Calcium dysregulation and neuroinflammation: discrete and integrated mechanisms for age-related synaptic dysfunction

Some of the best biomarkers of age-related cognitive decline are closely linked to synaptic function and plasticity. This review highlights several age-related synaptic alterations as they relate to Ca(2+) dyshomeostasis, through elevation of intracellular Ca(2+), and neuroinflammation, through production of pro-inflammatory cytokines including interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α). Though distinct in many ways, Ca(2+) and neuroinflammatory signaling mechanisms exhibit extensive cross-talk and bidirectional interactions. For instance, cytokine production in glial cells is strongly dependent on the Ca(2+) dependent protein phosphatase calcineurin, which shows elevated activity in animal models of aging and disease. In turn, pro-inflammatory cytokines, such as TNF, can augment the expression/activity of L-type voltage sensitive Ca(2+) channels in neurons, leading to Ca(2+) dysregulation, hyperactive calcineurin activity, and synaptic depression. Thus, in addition to discussing unique contributions of Ca(2+) dyshomeostasis and neuroinflammation, this review emphasizes how these processes interact to hasten age-related synaptic changes.

Antihypertensive medication use and risk of cognitive impairment: the Honolulu-Asia Aging Study

OBJECTIVE

To determine the associations between classes of antihypertensive medication use and the risk of cognitive impairment among elderly hypertensive men.

METHODS

The Honolulu-Asia Aging Study is a prospective, community-based cohort study of Japanese American men conducted in Honolulu, Hawaii. We examined 2,197 participants (mean age 77 years at cohort entry, 1991-1993, followed through September 2010) with hypertension and without dementia or cognitive impairment at baseline, who provided information on medication use. Cognitive function was assessed at 7 standardized examinations using the Cognitive Abilities Screening Instrument (CASI). Cognitive impairment was defined as a CASI score <74.

RESULTS

A total of 854 men developed cognitive impairment (median follow-up, 5.8 years). β-Blocker use as the sole antihypertensive drug at baseline was consistently associated with a lower risk of cognitive impairment (incidence rate ratio [IRR] 0.69; 95% confidence interval [CI] 0.50-0.94), as compared with men not taking any antihypertensive medications, adjusting for multiple potential confounders. The use of diuretics, calcium channel blockers, angiotensin-converting enzyme inhibitors, or vasodilators alone was not significantly associated with cognitive impairment. Results were similar excluding those with cardiovascular disease or <1 year of follow-up, and additionally adjusting for pulse pressure, heart rate, baseline and midlife systolic blood pressure, and midlife antihypertensive treatment (IRR 0.65; 95% CI 0.45-0.94). The association between β-blocker use and cognitive impairment was stronger among men with diabetes, men aged >75 years, and those with pulse pressure ≥70 mm Hg.

CONCLUSIONS

β-blocker use is associated with a lower risk of developing cognitive impairment in elderly Japanese American men.

Nimodipine-induced hypotension but not nitroglycerin-induced hypotension preserves long- and short-term memory in adult mice

BACKGROUND

Acute hypotension may be implicated in cognitive dysfunction. L-type calcium channel blockers in the setting of hypoxia are protective of learning and memory. We tested the hypothesis that hypotension induced by nimodipine (NIMO) and nicardipine (NICA) would be protective of long- and short-term memory compared to hypotension induced by nitroglycerin (NTG).

METHODS

Forty Swiss-Webster mice (30 to 35 g, 6 to 8 weeks) were randomized into 4 groups for i.p. injection immediately after passive avoidance (PA) learning on day 0: (1) NTG (30 mg/kg); (2) NICA (40 mg/kg); (3) NIMO (40 mg/kg); and (4) saline. PA training latencies (seconds) were recorded for entry from a suspended platform into a Plexiglas tube where a shock (0.3 mA; 2-second duration) was automatically delivered. On day 2 latencies were recorded during a testing trial during which no shock was delivered. Latencies >900 seconds were assigned this value. Lower testing latency is indicative of an impairment of long-term associative memory. Forty-nine additional mice were randomized into similar groups for object recognition testing (ORT) and given i.p. injections on day 0. ORT measures short-term memory by exploiting the tendency of mice to prefer novel objects where a familiar object is present. On day 5 during training, 2 identical objects were placed in a circular arena and mice explored both for 15 minutes. A testing trial was conducted 1 hour later for 3 minutes after a novel object replaced a familiar one. Mice with intact memory spend about 65% of the time exploring the novel object. Mice with impaired memory devote equal time to each object. Recognition index (RI) is defined as the ratio of time spent exploring the novel object to time spent exploring both objects was the measure of memory. Mean arterial blood pressure (MAP), cerebral bloodflow, and body and brain oxygenation (PO(2)) studies were done in separate groups of mice to determine the dosages for matched degrees of hypotension and the physiological profile of each treatment.

RESULTS

The median PA latencies for the different conditions were as follows: NTG (219.5 ± 93.5 second semi-interquartile range [SIQR]), NICA (372.5 ± 75.5 second SIQR), NIMO (540 ± 200 second SIQR) and saline (804 ± 257.5 second SIQR). Rank methods were used to analyze the PA latencies for significant differences. NTG latency was significantly shorter than NIMO latency (P = 0.012) and saline latency (P = 0.006), but not NICA latency (P = 0.126). ORT RI values showed a similar pattern. We found that NTG RI (47.2 ± 5.9% SEM) was different from NIMO RI (60.2 ± 4.6% SEM, P = 0.031) and different from saline RI (66.9 + 3.7% SEM, P = 0.006). Physiological experiments showed that MAP decreased to 45 to 50 mm Hg in all animals who became minimally responsive to external stimuli within 10 to 15 minutes of injection. Intergroup differences for MAP, body and brain oxygenation, and cerebral bloodflow were not statistically significant.

CONCLUSION

Acute hypotension induced by NIMO was protective of 2 categories of memory formation relevant to the clinical posttreatment period. Both immediate long-term associative memory consolidation as measured by the PA learning paradigm and delayed short-term working memory function as measured by the ORT paradigm were significantly improved compared to matched levels of hypotension induced by NTG. These results indicate the utility of further investigation of l-type calcium channel blockers as a potential means of preserving cognition in the setting of hypotensive and low flow states.