Received in December 2020; Similarity Check in December 2020; Accepted in June 2021 The aim of this study was to investigate the effects of oral melatonin on oxidative/antioxidative parameters and histopathological changes in the hippocampal tissue of Cd-exposed Wistar rats, including malondialdehyde (MDA), glutathione (GSH), tumour necrosis factor-alpha (TNF-a), interleukin (IL-6 and IL-10), and gamma-aminobutyric acid (GABA) levels and catalase (CAT), superoxide dismutase (SOD), and acetylcholinesterase (AChE) activities. KLJUČNE RIJEČI: acetilkolinesteraza; antioksidansi; CAT; Cd; citokini; GABA; GSH; hipokampus; IL-6; The main sources of occupational exposure to cadmium (Cd) are metal industries (mining, smelting, processing, product formulations, and battery manufacturing), while the sources of non-occupational exposure include contaminated air (smoking included), water, soil, plants, and food. To that effect the aim of our study was to compare common oxidative stress, inflammation, and neurotoxicity parameters malondialdehyde (MDA) (25), interleukins 6 and 10 (IL-6, IL-10), tumour necrosis factor alpha (TNF-a) (9, 26-28), GABA (29-36), acetylcholinesterase (AChE) (17, 37, 38) and antioxidant defence parameters glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) (39) in the hippocampal tissue of control, Cd-, and melatonintreated rats. MATERIALS AND METHODS Animals and experimental design Three weeks old male albino Wistar rats weighing ~200±30 g (n=32), purchased from Balıkesir University Experimental Medicine Research and Application Center (BUEMRAC), were first acclimatised to laboratory conditions for two weeks and then divided randomly into four groups: untreated control, cadmium (Cd), melatonin (Mlt), and Cd+Mlt (CdMlt), each consisting of eight animals.