Further analysis of the neuropharmacological profile of 9-amino-1,2,3,4-tetrahydroacridine (THA), an alleged drug for the treatment of Alzheimer's disease.

In a recent study we have documented the acetylcholinesterase and outward K+-current inhibiting activity of 9-amino-1,2,3,4-tetrahydroacridine (THA), a drug reportedly active in the treatment of Alzheimer patients. In the present study we investigated the effects of THA on the uptake and release of radiolabeled NA, DA and 5-HT. THA concentration-dependently inhibited the uptake of these monoamines with IC-50 values of approximately 1, 7 and 2 microM respectively. Release studies of these radiolabeled monoamines from control and reserpine pretreated tissue revealed that the THA-induced uptake inhibition does not occur at the level of the axonal membrane but at the level of the monoaminergic storage granules. In addition the affinity of THA for alpha-1, alpha-2 and beta-adrenoceptors, for D-2 dopamine, S-1a and S-2 serotonin and for muscarinic receptors was investigated. It appeared that in concentrations up to 1 microM THA did not display any affinity towards these receptors. It is concluded from these experiments that the effects of THA on monoaminergic neurotransmission might contribute to the alleged therapeutic action of THA in Alzheimer's disease.