Unravelling motor behaviour hallmarks in intoxicated adolescents: methylmercury subtoxic-dose exposure and binge ethanol intake paradigm in rats

Abstract

Methylmercury (MeHg) is a hazardous environmental pollutant, affecting Amazon basin communities by anthropogenic activities. The exact safe level of MeHg exposure is unclear, despite the efforts of health international societies to avoid mercury (Hg) poisoning. Central nervous system is severely impacted by Hg intoxication, reflecting on motor impairment. In addition, alcohol has been associated to an overall brain damage. According to lifestyle of Amazon riverside communities, alcohol intake occurs frequently. Thus, we investigated if continuous MeHg exposure at low doses during adolescence displays motor deficits (experiment 1). In the experiment 2, we examine if the co-intoxication (i.e. MeHg plus ethanol exposure) during adolescence intensify motor damage. In the experiment 1, Wistar adolescent rats (31 days old) received chronic exposure to low dose (CELD) of MeHg (40 μg/kg/day) for 35 days. For the experiment 2, five sessions of alcohol binge drinking paradigm (3ON-4OFF; 3.0 g/kg/day) were employed associated to MeHg intoxication. Motor behaviour was evaluated by the open field, pole test, beam walking and rotarod paradigms. CELDS of MeHg display motor function damage, related to hypoactivity, bradykinesia-like behaviour, coordination deficits and motor learning impairment. Co-intoxication of MeHg plus ethanol reduced cerebellar Hg content, however also resulted in motor behavioural impairment, as well as additive effects on bradykinesia and fine motor evaluation.

Physical Exercise Attenuates Oxidative Stress and Morphofunctional Cerebellar Damages Induced by the Ethanol Binge Drinking Paradigm from Adolescence to Adulthood in Rats

“…Moreover, at the beam walking test, animals that consumed alcohol presented worse motor performance characterized by higher number of falls and less ability for activities that required motor dexterity. These results corroborate those recently found in another study from our group, which demonstrated that binge episodes during adolescence impact motor performance [50, 52], as well as affect other brain areas, inducing an anxiogenic behavior and influencing short-term recognition memory [6]. We believe that ethanol consumption increased cerebral blood flow by increasing the metabolic oxygen demand, so that brain regions related to motor activity and central command network are affected.…”

Towards Therapeutic Alternatives for Mercury Neurotoxicity in the Amazon: Unraveling the Pre-Clinical Effects of the Superfruit Açaí (Euterpe oleracea, Mart.) as Juice for Human Consumption

“…Actually, the performance in the open field test is mainly related to the motor cortex [46]. In previous works with chronic exposure to MeHg, we demonstrated that mercury seems to be less present in the motor cortex and hippocampus in comparison with other areas of the brain, such as prefrontal cortex and cerebellum, of exposed animals [47,48]. In this sense, our hypothesis is that even with higher doses of MeHg, the four-days exposure in adult male mice used in this work is not sufficient to affect the motor cortex to produce significant changes in spontaneous exploration.…”

Effects of Fluoride Long-Term Exposure over the Cerebellum: Global Proteomic Profile, Oxidative Biochemistry, Cell Density, and Motor Behavior Evaluation

“…Animals that failed to turn, in other words, slid across the beam in the same position as they were placed on the equipment, or fell, even if they had already turned upside down, were given the maximum time (120 s). The average was calculated with the 3 best times of each animal [ 72 , 76 ].…”