Imidacloprid (IMI) is known to target the nicotinic acetylcholine receptors (nAChRs) in insects, and potentially in mammals. However, IMI toxicity on mammalian tissues has not been adequately evaluated. The aim of the present study was to examine whether IMI induced functional impairment in hypthalamic-pituitary-adrenal (HPA) axis tissues. An oral exposure of 40 mg IMI/kg for 28 days in male rats caused a significant increase in malondialdehyde (MDA) level. The antioxidant catalase, superoxide dismutase, and glutathione S-transferase showed various alterations following administration, but a significantly depleted thiol (SH) groups was only recorded in hypothalamic tissues. The increase in the relative weight of adrenal glands and the increased adrenal cholesterol and plasma adrenocorticotropic hormone (ACTH) levels are indicative of general adaptation syndrome. The hypothalamic and pituitary acetylcholinesterase activity and calcium level were significantly increased, highlighting the alteration of cholinergic transmission. In conclusion, the findings obtained show that chronic exposure to IMI may alter biochemical processes of HPA axis.
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