Resumen

ARVELAEZ, Lourdes  y  EBLEN-ZAJJUR, Antonio. Inhibition of butyrylcholinesterase induced by exposition to Malathion: effects on nociceptive and motor behavior in rats. Salus [online]. 2013, vol.17, n.2, pp.41-49. ISSN 1316-7138.

Due to cholinergic presence in the nociceptive system and the frequent exposition to Malathion, an organophosphorated pesticide with an Achetylcholinesterase inhibitory effect, the impact of the increased cholinergic tone induced by a low dose of malathion on the nociceptive and motor behavior of rats was tested. Male Sprague Dawley rats (350-400g) were divided into two groups: Control (n=10) injected with 1mL NaCl 0.9% daily (i.p.) and Malathion (n=10) injected with 1mL of malathion (40 mg.Kg^-1.day^-1, in NaCl 0.9%, i.p) daily for 7 days. At days 1, 4 and 7 of treatment the nociceptive threshold was evaluated by the hot-plate method at 50ºC, motor activity by total rat displacement in 5 min, and the plasmatic Butyrylcholinesterase (BuChE) activity as a cholinergic biomarker. BuChE activity progressively decreased by 23.6%; 48.9% and 53.2% at days 1, 4 and 7 of treatment, respectively, showing a logarithmic inhibitory kinetics: % of BuChE inhibition= 53.73 x (1+1,22^-0,81xday); r=0,93; P<0,05. The tested exposition dose was non-lethal in order to simulate chronic toxicity. Despite the BuChE inhibition, no statistical differences between both groups were found, neither for the nociceptive threshold (Controls:13.5±5,4; Malathion 15.2±6.5s; P>0.05; Mean±SD) nor for motor activity (Controls:108.5±30,1; malathion:102.1±43.9cm; P>0.05). These results strongly suggest that despite the intense BuChE inhibition induced by exposition to a low dose of malathion, the contribution of the cholinergic system in nociception is reduced or even marginal, which reveals the action of other neurotransmitters in this process.

Palabras clave : Malathion; organophosphate pesticides; cholinergic enzyme; butyrylcholinesterase; nociception.

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