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Using knockout (KO) mice lacking the histamine (HA)-synthesizing enzyme (histidine decarboxylase, HDC), we have previously shown the importance of histaminergic neurons in maintaining wakefulness (W) under behavioral challenges. Since the central actions of HA are mediated by several receptor subtypes, it remains to be determined which one(s) could be responsible for such a role. We have therefore compared the cortical-EEG, sleep and W under baseline conditions or behavioral/pharmacological stimuli in littermate wild-type (WT) and H1-receptor KO (H1-/-) mice. We found that H1-/- mice shared several characteristics with HDC KO mice, i.e. 1) a decrease in W after lights-off despite its normal baseline daily amount; 2) a decreased EEG slow wave sleep (SWS)/W power ratio; 3) inability to maintain W in response to behavioral challenges demonstrated by a decreased sleep latency when facing various stimuli. These effects were mediated by central H1-receptors. Indeed, in WT mice, injection of triprolidine, a brain-penetrating H1-receptor antagonist increased SWS, whereas ciproxifan (H3-receptor antagonist/inverse agonist) elicited W; all these injections had no effect in H1-/- mice. Finally, H1-/- mice showed markedly greater changes in EEG power (notably in the 0.8-5 Hz band) and sleep-wake cycle than in WT mice after application of a cholinergic antagonist or an indirect agonist, i.e., scopolamine or physostigmine. Hence, the role of HA in wake-promotion is largely ensured by H1-receptors. An upregulated cholinergic system may account for a quasi-normal daily amount of W in HDC or H1-receptor KO mice and likely constitutes a major compensatory mechanism when the brain is facing deficiency of an activating system. This article is part of the Special Issue entitled 'Histamine Receptors'. Copyright (C) 2015 Elsevier Ltd. All rights reserved.

International audience; BACKGROUND: Despite the high intake of medications with anticholinergic properties by community-dwelling elderly persons, the effects on cognitive decline and dementia have rarely been evaluated. METHODS: Participants were 4128 women and 2784 men 65 years or older from a population-based cohort recruited from 3 French cities. Cognitive performance, clinical diagnosis of dementia, and anticholinergic use were evaluated at baseline and 2 and 4 years later. RESULTS: A total of 7.5% of the participants reported anticholinergic drug use at baseline. Multivariate-adjusted logistic regression indicated that women reporting use of anticholinergic drugs at baseline showed greater decline over 4 years in verbal fluency scores (odds ratio [OR], 1.41; 95% confidence interval [CI], 1.11-1.79) and in global cognitive functioning (OR, 1.22; 95% CI, 0.96-1.55) than women not using anticholinergic drugs. In men, an association was found with decline in visual memory (OR, 1.63; 95% CI, 1.08-2.47) and to a lesser extent in executive function (OR, 1.47; 95% CI, 0.89-2.44). Notable interactions were observed in women between anticholinergic use and age, apolipoprotein E, or hormone therapy. A 1.4- to 2-fold higher risk of cognitive decline was observed for those who continuously used anticholinergic drugs but not for those who had discontinued use. The risk of incident dementia over the 4-year follow-up period was also increased in continuous users (hazard ratio [HR], 1.65; 95% CI, 1.00-2.73) but not in those who discontinued the use of anticholinergic drugs (HR, 1.28; 95% CI, 0.59-2.76). CONCLUSIONS: Elderly people taking anticholinergic drugs were at increased risk for cognitive decline and dementia. Discontinuing anticholinergic treatment was associated with a decreased risk. Physicians should carefully consider prescription of anticholinergic drugs in elderly people, especially in the very elderly and in persons at high genetic risk for cognitive disorder.

Acetylcholine (ACh) is known to shape the adult neocortical activity related to behavioral states and processing of sensory information. However, the impact of cholinergic input on the neonatal neuronal activity remains widely unknown. Early during development, the principal activity pattern in the primary visual (V1) cortex is the intermittent self-organized spindle burst oscillation that can be driven by the retinal waves. Here, we assessed the relationship between this early activity pattern and the cholinergic drive by either blocking or augmenting the cholinergic input and investigating the resultant effects on the activity of the rat visual cortex during the first postnatal weekin vivo. Blockade of the muscarinic receptors by intracerebroventricular, intracortical, or supracortical atropine application decreased the occurrence of V1 spindle bursts by 50%, both the retina-independent and the optic nerve-mediated spindle bursts being affected. In contrast, blockade of acetylcholine esterase with physostigmine augmented the occurrence, amplitude, and duration of V1 spindle bursts. Whereas direct stimulation of the cholinergic basal forebrain nuclei increased the occurrence probability of V1 spindle bursts, their chronic immunotoxic lesion using 192 IgG-saporin decreased the occurrence of neonatal V1 oscillatory activity by 87%. Thus, the cholinergic input facilitates the neonatal V1 spindle bursts and may prime the developing cortex to operate specifically on relevant early (retinal waves) and later (visual input) stimuli.

OBJECTIVE: To assess the potential of anticholinergic drugs as a cause of non-degenerative mild cognitive impairment in elderly people. DESIGN: Longitudinal cohort study. SETTING: 63 randomly selected general practices in the Montpellier region of southern France. PARTICIPANTS: 372 people aged > 60 years without dementia at recruitment. MAIN OUTCOME MEASURES: Anticholinergic burden from drug use, cognitive examination, and neurological assessment. RESULTS: 9.2% of subjects continuously used anticholinergic drugs during the year before cognitive assessment. Compared with non-users, they had poorer performance on reaction time, attention, delayed non-verbal memory, narrative recall, visuospatial construction, and language tasks but not on tasks of reasoning, immediate and delayed recall of wordlists, and implicit memory. Eighty per cent of the continuous users were classified as having mild cognitive impairment compared with 35% of non-users, and anticholinergic drug use was a strong predictor of mild cognitive impairment (odds ratio 5.12, P = 0.001). No difference was found between users and non-users in risk of developing dementia at follow-up after eight years. CONCLUSIONS: Elderly people taking anticholinergic drugs had significant deficits in cognitive functioning and were highly likely to be classified as mildly cognitively impaired, although not at increased risk for dementia. Doctors should assess current use of anticholinergic drugs in elderly people with mild cognitive impairment before considering administration of acetylcholinesterase inhibitors.

International audience; BACKGROUND: Despite the high intake of medications with anticholinergic properties by community-dwelling elderly persons, the effects on cognitive decline and dementia have rarely been evaluated. METHODS: Participants were 4128 women and 2784 men 65 years or older from a population-based cohort recruited from 3 French cities. Cognitive performance, clinical diagnosis of dementia, and anticholinergic use were evaluated at baseline and 2 and 4 years later. RESULTS: A total of 7.5% of the participants reported anticholinergic drug use at baseline. Multivariate-adjusted logistic regression indicated that women reporting use of anticholinergic drugs at baseline showed greater decline over 4 years in verbal fluency scores (odds ratio [OR], 1.41; 95% confidence interval [CI], 1.11-1.79) and in global cognitive functioning (OR, 1.22; 95% CI, 0.96-1.55) than women not using anticholinergic drugs. In men, an association was found with decline in visual memory (OR, 1.63; 95% CI, 1.08-2.47) and to a lesser extent in executive function (OR, 1.47; 95% CI, 0.89-2.44). Notable interactions were observed in women between anticholinergic use and age, apolipoprotein E, or hormone therapy. A 1.4- to 2-fold higher risk of cognitive decline was observed for those who continuously used anticholinergic drugs but not for those who had discontinued use. The risk of incident dementia over the 4-year follow-up period was also increased in continuous users (hazard ratio [HR], 1.65; 95% CI, 1.00-2.73) but not in those who discontinued the use of anticholinergic drugs (HR, 1.28; 95% CI, 0.59-2.76). CONCLUSIONS: Elderly people taking anticholinergic drugs were at increased risk for cognitive decline and dementia. Discontinuing anticholinergic treatment was associated with a decreased risk. Physicians should carefully consider prescription of anticholinergic drugs in elderly people, especially in the very elderly and in persons at high genetic risk for cognitive disorder.