ORIGINAL ABSTRACT

Clethodim (CL) is a cyclohexanedione oxime herbicide that inhibits acetyl-CoA carboxylase in grasses and is widely used to control glyphosate-resistant weeds. Despite its extensive agricultural application, information regarding its toxicological effects on non-target organisms remains limited. Therefore, this study evaluated the behavioral, metabolic, and neurochemical consequences of repeated CL exposure in rats. Adult male Wistar rats (6-8 months old; 300-500 g) were assigned to four groups: control (CTL; 0.9% saline), CL-0.06 (0.06%), CL-0.3 (0.3%), and CL-0.6 (0.6%). Animals were exposed to nebulized CL or saline every 48 h for a total of 25 sessions. Behavioral performance was assessed using the catalepsy, open field, novel object recognition, spontaneous alternation, and forced swim tests. Metabolic parameters included body mass, food intake, glucose tolerance, and relative organ mass. Following the experimental protocol, brains were processed for immunohistochemical analyses of brain-derived neurotrophic factor (BDNF) and choline acetyltransferase (ChAT). Repeated CL exposure induced behavioral, metabolic, and neurochemical alterations. The CL-0.06 group exhibited reduced catalepsy duration and decreased spleen mass. Animals exposed to CL-0.6 displayed impaired spontaneous alternation performance, increased body mass gain, and altered glucose tolerance. All CL-treated groups exhibited reduced food intake and increased immobility behavior in the forced swim test. Neurochemical analyses revealed reduced BDNF immunoreactivity in the hippocampal CA1 region in the CL-0.06 and CL-0.3 groups, whereas ChAT immunoreactivity remained unchanged in cholinergic nuclei. In conclusion, repeated exposure to CL promotes behavioral, metabolic, and region-specific neurochemical alterations, including reductions in BDNF immunoreactivity, supporting the hypothesis that this herbicide may exert neurotoxic effects in non-target organisms.