Beneficial Effect of Atomoxetine Treatment on Scopolamine-Induced Cognitive Impairments and Molecular Changes in Rats

Abstract

Objective: Atomoxetine is a noradrenaline re-uptake inhibitory drug that is currently used in the pharmacological treatment of attention deficit/hyperactivity disorder in children, adolescents, and adults. Based on the findings that noradrenergic system is closely associated with learning and memory processes, dysfunction of this system might contribute to the pathophysiology of cognitive disorders. Therefore, atomoxetine, which alters the noradrenergic neurotransmission in the synaptic cleft, has a potential to modulate learning and memory functions in various areas of the central nervous system. In the present study, it was aimed to investigate the effects of atomoxetine treatment on the cognitive impairments in amnesic animals using behavioral and immunohistochemical methods. Method: Male Sprague-Dawley rats (adult, weighing 250-300 g) were used in the experiments. Atomoxetine at doses of 3 or 6 mg/kg (i.p.) was administered to the rats for 14 days. Experimental amnesia was induced in the animals by applying scopolamine (0.5 mg/kg, i.p.) injection. Following the treatment protocol, Morris water maze and passive avoidance tests were conducted to assess spatial and emotional learning and memory parameters of rats, respectively. Piracetam (300 mg/kg daily for 14 days) was used as reference drug in these experiments. In addition, motor performances of the animals were evaluated by activity cage and Rota-rod tests. Subsequent to behavioral tests, rats were euthanized and immunohistochemical analyses were performed to determine the alterations in the BDNF and NGF levels in the hippocampi of the animals. Results: In the Morris water maze test, amnesic rats found the hidden platform slower and spent less time in the target quadrant compared to the healthy controls. On the other hand, atomoxetine treatments significantly decreased the escape latencies, and also increased the target quadrant time values of the amnesic animals at both doses. Data obtained from the passive avoidance test showed that second transition latency values of the amnesic rats were significantly shortened with respect to the control animals; while atomoxetine treatment prolonged these shortened values significantly. It was observed that atomoxetine did not alter motor coordination or spontaneous locomotor activities of animals. Moreover, this drug increased the BDNF and NGF levels in the hippocampal sub-regions which were diminished by scopolamine administration. Conclusions: The obtained findings showed that atomoxetine treatment significantly improved the impaired learning and memory performances of the rats induced by scopolamine administration. Furthermore, anti-amnesic effects of this drug were concomitant with increased neurotrophic factors levels in the hippocampal brain regions. These results suggest a notable therapeutic potential of this drug in the treatment of dementia and several cognitive disorders; however, it should be underlined they are needed to be confirmed by well-designed clinical trials.