Alzheimer's disease (AD) is a progressive neurodegenerative disorder of the elderly, characterised by widespread loss of central cholinergic function. The only symptomatic treatment proven effective to date is the use of cholinesterase (ChE) inhibitors to augment surviving cholinergic activity. ChE inhibitors act on the enzymes that hydrolyse acetylcholine (ACh) following synaptic release. In the healthy brain, acetylcholinesterase (AChE) predominates (80%) and butyrylcholinesterase (BuChE) is considered to play a minor role in regulating brain ACh levels. In the AD brain, BuChE activity rises while AChE activity remains unchanged or declines. Therefore both enzymes are likely to have involvement in regulating ACh levels and represent legitimate therapeutic targets to ameliorate the cholinergic deficit. The two enzymes differ in location, substrate specificity and kinetics. Recent evidence suggests that BuChE may also have a role in the aetiology and progression of AD beyond regulation of synaptic ACh levels. Experimental evidence from the use of agents with enhanced selectivity for BuChE (cymserine, MF-8622) and ChE inhibitors such as rivastigmine, which have a dual inhibitory action on both AChE and BuChE, indicate potential therapeutic benefits of inhibiting both AChE and BuChE in AD and related dementias. The development of specific BuChE inhibitors and the continued use of ChE inhibitors with the ability to inhibit BuChE in addition to AChE should lead to improved clinical outcomes.

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Polymer/liquid crystal (LC) composite films possessing an azobenzene LC as a photoresponsive molecule (AzoCFs) were prepared by the thermal polymerization-induced phase separation method. The composite films (AzoCFs) showed a strong light-scattering state after polymerization, and their optical properties were strongly affected by the compositional ratio of the liquid crystals in the composite film. Change in the transmittance between a light-scattering and a transparent state could be induced isothermally by photoirradiation. Upon irradiation at 366 nm, AzoCFs changed from the light-scattering state to the transparent state. This is ascribed to nematic (N)-isotropic (I) phase transition due to transcis isomerization of the azobenzene molecules in the LC domains within the polymer matrix. Furthermore, restoration of the initial state could be achieved by visible-light irradiation (>420 nm), resulting from the I-N phase transition induced by cis-trans back-isomerization of the azobenzene guest molecules.