Cognitive Enhancers tacrine

Chopin P, Briley M. (1992). Effects of four non-cholinergic cognitive enhancers in comparison with tacrine and galanthamine on scopolamine-induced amnesia in rats. Psychopharmacoiogy (Beriin). 106(1) 26-30. 

Tacrine (= Cognex 1,2,3,4-Tetrahydro-5- aminoacridine)] (acridine) Synthetic nACh-R ligand (AAhE, BChE) [esp. AD amyloid plaque- tangle-associated ChE clinical cognition enhancer for AD]... 

Tacrine has been found to be somewhat effective in patients with mild-to-moderate symptoms of this disease for improvement of cognitive functions. The drug is primarily a reversible cholinesterase inhibitor that increases the concentration of functional ACh in the brain. However, the pharmacology of tacrine is complex the drug also acts as a muscarinic receptor modulator in that it has partial agonistic activity, as well as weak antagonistic activity on muscarinic receptors in the CNS. In addition, tacrine appears to enhance the release of ACh from cholinergic nerves, and it may alter the concentrations of other neurotransmitters such as dopamine and NE. 

The only clinically available cholinergic therapy to date is an anticholinesterase (tacrine). Studies have shown short-term improvement in some aspects of memory and a delay in decline in some patients. It has been generally assumed that these effects are solely the result of enhancement of muscarinic mechanisms however, this assumption may be unwarranted. Direct muscarinic augmentation produces little measurable cognitive improvement and does not generally reproduce the memory-enhancing effects of anticholinesterases (Bruno et al. 1986 Tariot et al. 1988). 

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