A 15-day course of donepezil modulates spectral EEG dynamics related to target auditory stimuli in young, healthy adult volunteers

Functional connectivity and cognitive changes after donepezil treatment in healthy participants

RATIONALE

Donepezil is a potent, noncompetitive, reversible, clinically effective acetylcholinesterase inhibitor. The effects of this drug on healthy brains have seldom been investigated.

OBJECTIVES

The primary objective of the present study was to identify possible functional connectivity markers of the effect of donepezil in healthy young adult volunteers.

METHODS

The study had a double-blind, randomized, crossover design. 30 healthy adult volunteers underwent resting-state MRI scans during 15 days of donepezil or placebo treatment, in accordance with the design.

RESULTS

Results showed significant differences in intrinsic functional connectivity between donepezil and placebo, mainly in the right executive control network (RECN). More specifically, we found a decrease in the connectivity of the right inferior parietal node with other RECN nodes. Analysis using the cingulate cortex and parahippocampal regions as seeds also revealed complex modulation of functional connectivity in the donepezil condition.

CONCLUSIONS

In conclusion, donepezil treatment for 15 days may result in reorganization of resting-state networks, compared with placebo.

Innovative approaches in CNS clinical drug development: Quantitative systems pharmacology

Clinical trials involving brain disorders are notoriously difficult to set up and run. Innovative ways to develop effective prevention and treatment strategies for central nervous system (CNS) diseases are urgently needed. New approaches that are likely to renew or at least modify the paradigms used so far have been recently proposed. Quantitative systems pharmacology (QSP) uses mathematical computerized models to characterize biological systems, disease processes and CNS drug pharmacology. Integrated experimental medicine should increase the probability and predictability of success while controlling clinical trials costs. Finally, the societal perspective and patient empowerment also offer additional approaches to demonstrate the benefit of a new drug in the CNS field.

Safety, pharmacokinetics, and pharmacodynamics of Gln-1062, a prodrug of galantamine

Introduction

Gln-1062 (MEMOGAIN) is an intranasally administered lipophilic prodrug of galantamine. Based on high brain-to-blood concentrations observed in pre-clinical studies, Gln-1062 is expected to have superior cognitive efficacy compared to oral galantamine.

Methods

Forty-eight healthy elderly subjects were randomized 12:4 to Gln-1062 (5.5, 11, or 22 mg, b.i.d., for 7 days) or placebo. Safety, tolerability, pharmacokinetics, and pharmacodynamics were assessed repeatedly. Pharmacokinetics were compared with 16 mg oral galantamine.

Results

Gln-1062 up to 22 mg, b.i.d., was well tolerated. Gln-1062 plasma concentrations increased immediately following dosing (median T_max of 0.5 hour [range 0.5-1.0]). C_max and AUC_0-last increased in a dose-linear manner over all three dose levels. Gln-1062 was rapidly cleaved into galantamine. Gln-1062 significantly improved adaptive tracking (sustained attention) with 1.95% (95% confidence interval [CI] 0.630-3.279, P = 0.0055) compared to placebo after correction for individual baseline performance.

Discussion

Gln-1062 was considered to be safe and caused fewer gastrointestinal side effects than oral galantamine. Gln-1062 behaved pharmacokinetically as expected and improved performance on cognitive tests.

Cholinergic potentiation of visual perception and vision restoration in rodents and humans

BACKGROUND

The cholinergic system is a potent neuromodulator system that plays a critical role in cortical plasticity, attention, and learning. Recently, it was found that boosting this system during perceptual learning robustly enhances sensory perception in rodents. In particular, pairing cholinergic activation with visual stimulation increases neuronal responses, cue detection ability, and long-term facilitation in the primary visual cortex. The mechanisms of cholinergic enhancement are closely linked to attentional processes, long-term potentiation, and modulation of the excitatory/inhibitory balance. Some studies currently examine this effect in humans.

OBJECTIVE

The present article reviews the research from our laboratory, examining whether potentiating the central cholinergic system could help visual perception and restoration.

METHODS

Electrophysiological or pharmacological enhancement of the cholinergic system are administered during a visual training. Electrophysiological responses and perceptual learning performance are investigated before and after the training in rats and humans. This approach's ability to restore visual capacities following a visual deficit induced by a partial optic nerve crush is also investigated in rats.

RESULTS

The coupling of visual training to cholinergic stimulation improved visual discrimination and visual acuity in rats, and improved residual vision after a deficit. These changes were due to muscarinic and nicotinic transmissions and were associated with a functional improvement of evoked potentials. In humans, potentiation of cholinergic transmission with 5 mg of donepezil showed improved learning and ocular dominance plasticity, although this treatment was ineffective in augmenting the perceptual threshold and electroencephalography.

CONCLUSIONS

Potential therapeutic outcomes ought to facilitate vision restoration using commercially available cholinergic agents combined with visual stimulation in order to prevent irreversible vision loss in patients. This approach has the potential to help a large population of visually impaired individuals.

Cholinergic Mechanisms of Target Oddball Stimuli Detection: The Late "P300-Like" Event-Related Potential in Rats

Event-related potentials (ERPs) and oscillations (EROs) provide powerful tools for studying the brain's synaptic function underlying information processing. The P300 component of ERPs indexing attention and working memory shows abnormal amplitude and latency in neurological and psychiatric diseases that are sensitive to pharmacological agents. In the active auditory oddball discriminant paradigm, behavior and auditory-evoked potentials (AEPs) were simultaneously recorded in awake rats to investigate whether P300-like potentials generated in rats responding to rare target oddball tones are sensitive to subcutaneous modulation of the cholinergic tone by donepezil (1 mg/kg) and scopolamine (0.64 mg/kg). After operant training, rats consistently discriminate rare target auditory stimuli from frequent irrelevant nontarget auditory stimuli by a higher level of correct lever presses (i.e., accuracy) in target trials associated with a food reward. Donepezil attenuated the disruptive effect of scopolamine on the level of accuracy and premature responses in target trials. Larger P300-like peaks with early and late components were revealed in correct rare target stimuli trials as compared to frequent tones. Donepezil enhanced the peak amplitude of the P300-like component to target stimuli and evoked slow theta and gamma oscillations, whereas scopolamine altered the amplitude of the P300-like component and EROs to target stimuli. Pretreatment with donepezil attenuated effects of scopolamine on the peak amplitude of the P300-like component and on EROs. This study provides evidence that AEP P300-like responses can be elicited by rats engaged in attentive and memory processing of target stimuli and outline the relevance of the cholinergic system in stimulus discrimination processing. The findings highlight the sensitivity of this translational index for investigating brain circuits and/or novel pharmacological agents, which modulate cholinergic transmission associated with increased allocation of attentional resources.