Alzheimer's Disease and the Pivotal Role of the Hypothalamus and the Intrinsic Opioid System

Sleep Disturbance in Mild Cognitive Impairment and Association With Cognitive Functioning. A Case-Control Study

Objectives: The aims of the current study are to (1) report the frequency of specific sleep disturbance symptoms in Mild Cognitive Impairment (MCI) and cognitive healthy older persons; (2) examine whether overall poor sleep and specific sleep disturbance symptoms are more common in persons with MCI compared to cognitive healthy older controls and; (3) examine the association between sleep disturbances and performance in general and specific cognitive domains in persons with MCI and separately in cognitive healthy older persons.

Methods: Data were collected at the Fondazione Ospedale San Camillo Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Venice, Italy as part of the European VPH-DARE@IT project. We included 69 persons with MCI (mean age 75.7; SD = 7.7) and 72 sex-matched cognitively healthy controls (mean age 71.8; SD = 7.0). Participants underwent extensive neuropsychological assessment and evaluation of subjective sleep performance with the Sleep Continuity in Alzheimer’s Disease Scale(SCADS).

Results: A fifth of MCI patients (21.7%, n = 15) had poor sleep compared to 15.3% (n = 11) of cognitively healthy controls. MCI patients had a 3.2 higher odds of having poor sleep compared to cognitively healthy controls after adjustment for age, education, sex, and general cognitive functioning (Odds Ratio (OR) = 3.2; 95% Confidence Interval (CI) = 1.1–9.2). Persons who reported waking up twice or more during the night had higher odds of being MCI compared to those who never wake or wake only once (OR = 2.6; 95% CI = 1.1–6.1). In MCI patients, poor sleep was associated with better general cognitive functioning and short-term working memory, whereas in cognitive healthy older persons poor sleep was associated with impairment in episodic memory performance and executive functioning.

Discussion: Our results confirm previous studies showing that sleep disturbances are common in MCI, and this may be due to an ongoing neurodegenerative process rather than a symptom of cognitive impairment. Future research with objective sleep measurements are needed in MCI as well as interventions to improve sleep with the aim of preventing cognitive decline.

Expression of nitric oxide system in clinically evaluated cases of Alzheimer's disease

The expression of neuronal nitric oxide (nNOS) and inducible nitric oxide (iNOS) as isoforms of the nitric oxide synthase (NOS) as well as nitrotyrosine as an end product of protein nitration was analyzed in sections of temporal cortex taken from postmortem brains of patients with Alzheimer's disease (AD). The patients were evaluated by the Clinical Dementia Rating scale (CDR0-CDR3) and studied in the Memory and Aging Project (MAP) of the Washington University Alzheimer Disease Research Center (ADCR). With the use of immunocytochemical procedures, neurons immunoreactive to nNOS were found to show large and small multipolar and pyramidal morphologies over the entire chronic AD evolution. The iNOS and nitrotyrosine immunoreactivities were also found in pyramidal-like cortical neurons and glial cells. Here, we speculate on the interaction among all specific neurodegenerative changes in AD and nitric oxide as an additional contribution to neuronal death in AD.

The placebo effect on mood and behavior: the role of the endogenous opioid system

Evidence from clinical and experimental studies has shown that placebos influence mood and behavior, that endogenous opioids are involved in the placebo effect, and that the endogenous opioid system is related to psychological events. Recent studies have also demonstrated that the endogenous opioid system is closely connected with other neurotransmitter systems in the brain. The author suggests that the interaction between the endogenous opioid system and different neurotransmitter systems in the brain mediates the placebo effect on mood and behavior of both healthy and sick people.

Neuropeptide changes in cortical and deep gray structures in Alzheimer's disease

The alteration of certain neuropeptide levels is a dramatic and consistent finding in the brains of AD patients. Levels of SS, which is normally present in high concentrations in cerebral cortex /75/, are consistently decreased in the neocortex, hippocampus and CSF of AD patients. In addition, decreased levels of SS correlate regionally with the distribution of neurofibrillary tangles in AD /47/. Most available evidence suggests that the subset of SS-containing neurons which lack NADPH diaphorase may be relatively vulnerable to degeneration in AD. CRF is another neuropeptide with frequently observed changes in AD. Levels of CRF, which is normally present in low concentrations in cortical structures /75/, are decreased in the neocortex and hippocampus of AD patients. However, levels of CRF in the CSF of AD patients are not consistently reduced, but this is likely a reflection of the relatively low levels of CRF normally present in cerebral cortex. Studies of deep gray structures in AD brains reveal elevated levels of GAL in the nucleus basalis. The ability of GAL to inhibit cholinergic neurotransmission has generated considerable interest, since degeneration of cholinergic neurons in the basal forebrain consistently occurs in AD. In addition, the presence of NADPH diaphorase in GAL-containing neurons may underlie the relative resistance of these neurons to degeneration. From the aforementioned studies, it appears that the neurons which are relatively resistant to neurodegeneration in AD contain NADPH diaphorase. It is hypothesized that the presence of NADPH diaphorase protects these neurons from neurotoxicity mediated by glutamate or nitric oxide. Although one recent study /147/ has reported an elevation of the microtubule-associated protein tau in the CSF of AD patients (and this could become a useful antemortem diagnostic tool for AD), no similar CSF abnormality has been found for any of the neuropeptides. Thus, the measurement of CSF neuropeptide levels presently remains unhelpful in the diagnosis and treatment of AD. Future research on neuropeptides and their potential roles in the pathogenesis, diagnosis, and treatment of AD will likely involve further development of pharmacological modulators of neuropeptide systems, together with the further study of brain neuropeptidases.

Alz-50 immunoreactivity in the hypothalamus of the normal and Alzheimer human and the rat

Alz-50 is a monoclonal antibody recognizing a 68 kilodalton protein that is abundant in Alzheimer's disease (AD) but not detectable by immunoblotting methods in normal brains. When used for immunohistochemistry in AD cortex, Alz-50 recognizes large numbers of neurofibrillary tangles (NFT), neuritic plaques, and some neurons that show no evidence of neurofibrillary degeneration by conventional histopathological staining methods. Alz-50 immunoreactivity is described at the light and electron microscopic levels in the hypothalamus of brains obtained at autopsy from normal and AD subjects. Alz-50 immunoreactivity in the rat hypothalamus is also described. A well-defined population of Alz-50 immunoreactive hypothalamic neurons was identified in both the normal human and rat. At the light microscopic level in the normal human, immunoreactive neurons were most concentrated in the periventricular region, but were also scattered throughout the arcuate nucleus (ARC), lateral hypothalamic area, and tuberal region. Immunoreactive fibers were seen in the periventricular region, dorsal division of the ventromedial nucleus (VMNd), ARC, and external layer of the median eminence (ME). In the rat, reactive neurons were seen only in the periventricular region, and reactive fibers were seen in the periventricular zone, medial preoptic nuclear complex, suprachiasmatic nucleus, VMNd, ARC, and external layer of the ME. Ultrastructurally, all immunoreactivity in the normal human and rat hypothalamus was associated with intraneuronal vesicles. In the AD hypothalamus, Alz-50 identified numerous senile plaques and NFT in addition to the cells and fibers that were stained in the normal brains. Immunoreactive plaques and NFT were most numerous in regions previously reported to undergo neurofibrillary degeneration. At the ultrastructural level, the immunoreactivity in the AD hypothalamus was associated with filaments as well as vesicles. The significance of the selective staining of a specific population of vesicles by Alz-50 is unknown; however, the present results suggest that it is independent of AD pathology.

Possible role of pineal melatonin in the mechanisms of aging

The pineal gland has captured man's attention as early in recorded history as the Greeks when philosophers considered it the "seat of the soul". Descartes, in the Middle Ages, furthered this concept naming it "esprits animaux" or, in current language, the psychic and somatic activating principle. These notions about the pineal gland were initially purely speculative and unsupported by scientific facts. However, with the development of a sound knowledge base concerning the pineal gland over the past twenty years, evidence has accumulated to suggest a pivotal role for the pineal in the 'fine tuning' and integrating of various neural and endocrine functions. The secretion of pineal melatonin has been shown to decline progressively with age. Recent hypotheses of aging have suggested that cumulative neuronal insults associated with free radical production may be associated with the process of aging. There is evidence to suggest that melatonin may protect against the age processes in part by attenuating the effects of free radical-induced neuronal damage. Other studies derived mainly from observations on pinealectomized rats also suggest that diminished melatonin secretion may be associated with acceleration of the aging process. Thus, pineal melatonin may be a natural anti-aging hormone.

Endogenous opiates: 1987

This paper is the tenth installment of our annual review of the research during the past year involving the endogenous opiate system. It covers the nonanalgesia and behavioral studies of the opiate peptides published in 1987. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal and renal activity; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical activity; locomotor activity; sex, pregnancy, and development; immunology and cancer; and other behavior.