Brain Research Bulletin 81 (2010) 641–646 Contents lists available at ScienceDirect Brain Research Bulletin journal homepage: www.elsevier.com/locate/brainresbull Research report Nitric oxide synthase inhibitors protect cholinergic neurons against AlCl 3 excitotoxicity in the rat brain Ivana D. Stevanovi ´ c a,∗ , Marina D. Jovanovi ´ c a , Miodrag ˇ Coli ´ c a , Ankica Jelenkovi ´ c b , Dubravko Bokonji ´ c c , Milica Ninkovi ´ c a a Military Medical Academy, Institute for Medical Research, Belgrade, Rudniˇ cka 6/8, 11 000 Belgrade, Serbia b Institute for Biological Research, Belgrade, Serbia c Military Medical Academy, Institute for Toxicology, Belgrade, Serbia article info Article history: Received 5 January 2010 Accepted 6 January 2010 Available online 11 January 2010 Keywords: Acetylcholine esterase Aluminium Behavior Nitric oxide synthase inhibitors abstract The present experiment was carried out to determine the effectiveness of nitric oxide synthase inhibitors: 7-nitroindazole and aminoguanidine in modulating the toxicity of aluminium chloride on acetylcholine esterase activity, as well as behavioural and morphological changes of Wistar rats. For biochemical anal- ysis the animals were killed 10 min, 3 h, 3 days and 30 days after the treatment and forebrain cortex, striatum, basal forebrain and hippocampus were removed. The biochemical changes observed in neuronal tissues show that nitric oxide synthase inhibitors exert as protective action in aluminium chloride-treated animals. In the present study, active avoidance learning was significantly impaired after aluminium chlo- ride injection, while pretreatment with nitric oxide synthase inhibitors prevented the behavioural deficits caused between 26th and 30th day after intrahippocampal application of neurotoxin. Our data suggest that aluminium may cause learning and memory deficits, while the treatment with specific nitric oxide synthase inhibitors may prevent learning and memory deficits caused by aluminium chloride. We have also applied immunohistochemical techniques to identify neuronal- and inducible-nitric oxide synthase expression 30 days after aluminium chloride and nitric oxide synthase inhibitors injections. Our data suggest that 7-nitroindazole and aminoguanidine can be effective in the protection of toxicity induced by aluminium chloride. © 2010 Elsevier Inc. All rights reserved. 1. Introduction Aluminium compounds are neurotoxic and have been shown to induce experimental neurodegeneration although the mecha- nism of this effect is unclear [9]. Aluminium is transported by the iron-carrier protein, transferrin that enters the brain by binding to transferrin receptors [39]. Aluminium exposure may exacerbate underlying events associated with brain aging and thus could con- tribute to progression of neurodegeneration [6]. Aluminium has the ability to produce neurotoxicity by many mechanisms, promot- ing formation and accumulation of insoluble beta-amyloid peptide (Abeta) and hyperphosphorylated tau [15]. Aluminium induces conformational changes of Abeta protein enhancing its aggrega- tion and leading to progressive neuronal degeneration and death [24,26]. The senile plaques are generated by brain deposition of fib- rils of Abeta, a fragment derived from the proteolytic processing of the amyloid precursor protein (APP) [32]. Tau protein is the major component of paired helical filaments, which form a compact fila- ∗ Corresponding author. Tel.: +381 11 2434960; fax: +381 11 2662722. E-mail address: ivanav13@yahoo.ca (I.D. Stevanovi ´ c). mentous network described as neurofibrillary tangles [20]. Also, to some extent, aluminium mimics the deficit of cortical cholinergic neurotransmission [25]. Aluminium exerts its toxic effects by altering cholinergic trans- mission, which is ultimately reflected in neurobehavioral deficits [14]. The dysfunction of cholinergic neurons is believed to be primarily responsible for cognitive deficits after intracerebral alu- minium intoxication [37]. Cholinergic neurons, unlike other brain cells utilize acetyl-CoA not only for energy production but also for acetylcholine (ACh) synthesis. Therefore, suppression of acetyl- CoA metabolism by different neurotoxic inputs may be particularly harmful for this group of cells [36]. Studies in vitro have suggested that acetylcholine esterase (AChE), a marker of cholinergic system function, may interact with Abeta to promote deposition of amyloid plaques in the brain after aluminium intoxication [28]. Acetylcholine and nitric oxide (NO) are important neuromod- ulators implicated in brain plasticity and disease [30]. The use of NO donors and NO synthase (NOS) inhibitors as pharmacologi- cal tools revealed that this free radical is probably implicated in the regulation of excitability and firing, in long-term potentiation and long-term depression, as well as in memory processes [11]. Moreover, NO modulates neurotransmitter release. In vivo and in 0361-9230/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.brainresbull.2010.01.004