Tetrahydroaminoacridine increases acetylcholine synthesis and glucose oxidation by mouse brain slices in vitro

Effects of MCI-225 on memory and glucose utilization in basal forebrain-lesioned rats

The effects of MCI-225 on amnesia, the cerebral glucose metabolism, and choline acetyltransferase (ChAT) activity in basal forebrain (BF)-lesioned rats were studied in comparison with those of tacrine. Bilateral BF lesions with ibotenic acid impaired the performance in passive avoidance (PA) tasks. Single administration of MCI-225 (10 mg/kg, PO) after a 2-week postoperative recovery period, increased the escape latencies in the PA task, but was not statistically significant. Repeated administration of MCI-225 (0.3 and 1 mg/kg, PO for 6 days) significantly reversed the PA failure. The BF-lesioned rat exhibited a marked decrease in the local cerebral glucose utilization (LCGU) in the frontal cortex, parietal cortex, and caudate-putamen. MCI-225 (1 mg/kg, PO for 5 days) significantly ameliorated the reduction of the LCGU in the parietal cortex. MCI-225 did not change the decrease in the cortical ChAT activity induced by the BF lesion. Repeated administration of tacrine reversed the PA failure (0.3 mg/kg, PO) but failed to prevent the decrement in the LCGU and the ChAT activity. These results suggest that MCI-225 could be effective in the treatment of senile dementia of the Alzheimer type, which is accompanied with both deficit in the BF-cortex cholinergic neuron and cerebral glucose hypometabolism.

Tacrine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in Alzheimer's disease

Tacrine is a centrally acting cholinesterase inhibitor with additional pharmacological activity on monoamine levels and ion channels. It has been postulated that some or all of these additional properties may also be relevant to the mode of action of the drug. There are wide interindividual variations in pharmacological and clinical response to tacrine, possibly related to interindividual variation in bioavailability. Tacrine appears to improve cognitive function and behavioural deficits in a proportion of patients with Alzheimer's disease, at dosages of 80 to 160 mg/day. In the best designed trials, 30 to 51% of evaluable patients showed an improvement of at least 4 points on the cognitive subscale of the Alzheimer's Disease Assessment Scale, versus 16 to 25% of placebo recipients. A similar proportion of tacrine recipients were judged to have improved when global assessment scales were used. There was a significant dose-response relationship up to 160 mg/day. However, large numbers of patients were withdrawn during the trials, many because of tacrine-associated increases in transaminase levels. Elevated liver enzyme levels occurred in about 50% of tacrine recipients (reaching clinical significance in about 25%). Cholinergic symptoms also occurred more often in tacrine recipients than in those receiving placebo. A gradual increase in tacrine dosage, at 6-week intervals, is recommended when initiating therapy, and weekly serum transaminase monitoring is required for 6 weeks after each dosage increase. Despite the limitations implied by the low proportion of responders and high incidence of hepatic adverse effects associated with therapy, tacrine appears to make a measurable difference in both cognitive and behavioural function in a proportion of patients with Alzheimer's disease--a welcome advance in an area previously devoid of acceptable treatment options.

Effectiveness of 1,2,3,4-tetrahydro-9-aminoacridine (THA) as a pretreatment drug for protection of mice from acute diisopropylfluorophosphate (DFP) intoxication

The protective action of 1,2,3,4-tetrahydro-9-aminoacridine (THA) against acute diisopropylfluorophosphate (DFP) intoxication was evaluated in mice by measuring the effects of the pretreatment of the animals with various doses of the drug on the DFP LD50. In the same experiments, the action of physostigmine and pyridostigmine were compared. THA at the doses 2.5, 5 and 7.5 mg/kg injected subcutaneously 15 min before DFP caused a dose-dependent increase in the DFP LD50, resulting in protection ratios equal to 3, 3.1 and 4.4, respectively, in the absence of atropine and 4.5, 8.6 and 14.5, respectively, in the absence of atropine and 4.5, 8.6 and 14.5, respectively, in the presence of atropine sulfate (17.4 mg/kg) therapy. Under the same experimental conditions, the protective ratios of 0.1 mg/kg physostigmine and pyridostigmine were 2.2 and 1.3, respectively, without atropine and 11.0 and 12.2, respectively, with atropine. The effectiveness of THA antidotal effect was inversely correlated to the time between pretreatment and DFP administration, being maximal when THA was injected 15 min before poisoning. In separate experiments, the time-course of acetylcholinesterase (AChE; EC 3.1.1.7) activity recovery was evaluated in the whole brain and diaphragm tissues of mice pretreated with THA (5 mg/kg) and physostigmine (0.1 mg/kg) 15 min before poisoning with DFP (8 mg/kg). At 10 min after DFP administration residual AChE activity in the brain averaged 4, 25 and 15% of that in controls in the animals pretreated with atropine alone, atropine plus THA or atropine plus physostigmine, respectively. At 24 h after poisoning, brain AChE activity averaged 34 and 47% of that in controls in the mice protected by THA and physostigmine, respectively. As for the diaphragm, AChE activity in THA-pretreated animals was 29% of controls 10 min after poisoning versus 8 and 23% in unprotected and physostigmine-pretreated animals, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)