Potential neurotoxicity of a novel aminoacridine analogue

Abstract

1 A class of compounds, 9-aminoacridines, have long been known to be reversible inhibitors of acetyl cholinesterase (AChE - EC 3.1.1.7), the most familiar of which is 9-amino-1,2,3,4-tetrahydroacridine (Tacrine).

2 A novel aminoacridine was synthesised: - 2-tertiary butyl-9-amino-1,2,3,4-tetrahydroacridine (2tBuTHA).

3 In vitro comparisons of the acetylcholinesterase inhibitory potential and neurotoxicity compared to Tacrine were performed using a chemically differentiated neuroblastoma cell line (Neuro 2A). 2tBuTHA, but not Tacrine, was cytotoxic to the neural cell following 20 h exposure, despite being the least potent AChE inhibitor (IC₈₀ AChE 12.53 μM +/- 1.14 s.e.m., Neutral Red Uptake IC₅₀ 9.53 μM +/- 0.98 s.e.m., MTT Reduction IC₈₀ 14.6 μM +/- 1.43 s.e.m.).

4 In vivo studies used a novel application of a five arm radial maze to assess neuropharmacological effects on working memory in control and Scopolamine (1 mg kg^-1 i.p.) treated mice. There was an impairment of short term cognitive function with 2tBuTHA (15 mg kg ^-1 i.p.), but not Tacrine (10 mg kg^-1 i.p.) which improved the Scopolamine deficit as expected.

5 This combined in vitro and in vivo data infers a neuro toxic property for the novel compound 2tBuTHA, a close structural analogue of Tacrine.