Retina, cholinesterase

Francis1 has successfully used D.F.P. in the histological localization of cholinesterases in the retina of the eye. 

Francis placed strips of the retina from different animals in sodium sulphate to precipitate the cholinesterase in situ. Some strips were then incubated with acetylthiocholine, while others were kept in D.F.P. solution before the incubation. The tissues after preliminary washings were then treated with appropriate reagents so as to precipitate the copper derivative of thio-choline. The sections ultimately obtained showed dark deposits at those points where the enzyme was present, and deposits were absent if D.F.P. had destroyed the enzyme. As a result of the application of this technique, Francis was able to establish that for all the animals examined, except the frog, true cholinesterase was present only at the inner synaptic layer. 

A reactivation of 23.9% of the Inhibited cholinesterase In the retina by I was accompanied by one of only 3.7% In the brain. If IV produces less reactivation of Inhibited cholinesterase in the brain than... 

Layer PG, Berger J, Kinkl N. 1997. Cholinesterases precede ON-OFF channel dichotomy in the embryonic chick retina before onset of synaptogenesis. CeU Tissue Res 288 407-416. 

Tacrine (9-amino-1,2.3,4-tetrahydroacride hydrochloride hydrate) is a cholinesterase inhibitor of potential use in Alzheimer s disease, based on the ability to facilitate cholinergic function in the CNS via direct stimulation of M- and N-receptors through inhibition of AChE (Avery et al, 1997 Newhouse et uL, 1997). Since ACh plays a fundamental role in visual function (Famiglictti, 1983 Hutchins, 1987 Ross et al, 1985), and because some visual. symptoms and optic nerve degeneration occur in Alzheimer s disease patient-s (Hinton et al., 1986) and the decrease in ACh found in the CNS may also occur in the retina (Strenn et ai, 1991), it was considered appropriate by Alhomida et al, (2000) to investigate the effects of tacrine on human retinal AChE activity. In vitro studies on human retinal homogenates showed a concentration-dependent inhibition of AChE activity by tacrine, with an... 

---