D. Warburton, K. Brown
2004
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24
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Journal
Psychopharmacologia
Abstract
In order to assess the effects of physostigmine sulphate on stable discrimination performance, a group of rats were trained on a simple brightness discrimination and injected with saline and three doses of the drug according to a latin square design. Improved performance was obtained with 0.05 and 0.10 mg/kg doses of the drug while the highest dose of 0.20 mg/kg impaired the discrimination responding. The effects of the highest dose were similar to the results obtained after injections of scopolamine hydrobromide into the same animals. A signal detection analysis revealed that physostigmine sulphate at the two low doses increased the stimulus sensitivity index without changes in the response bias index. These results were consistent with the hypothesis that physostigmine sulphate improved “attention” to the stimuli rather than response inhibition.A biochemical assay of brain cholinesterase activity showed that these two doses produced between 40% and 60% inhibition of activity, which is thought to be the critical levels for neural facilitation.