Peripubertal exposure of atrazine cause decrease in exploratory activity, deficits in sociability and few alterations on brain monoaminergic systems of rats

Atrazine is a pesticide used to control weeds in both in pre- and post-emergence crops. The chronic exposure to atrazine can lead to severe damage in animals, especially in the endocrine and reproduction systems, leading to the inclusion of this pesticide into the endocrine disrupting chemicals group. Studies with rats showed that atrazine exposure during lactation in dams caused changes in the juvenile offspring, however; there is still limited information regarding the effects of atrazine during puberty. Thus, the aim of this study is to evaluate the effects of peripubertal exposure of atrazine in rats, assessing motor activity, social behavior and neurochemical alterations. Juvenile rats were treated with different doses of atrazine (0, 10, 30 or 100 mg/kg) by gavage from postnatal day 22 to 41. Behavioral tests were conducted for the evaluation of motor activity and social behavior, and neurochemical evaluation was done in order to assess monoamine levels. Atrazine caused behavioral alterations, evidenced by decrease in the exploratory activity (p values variation between 0.05 and 0.0001) and deficits in the social behavior of both male and females as adults (p values variation between 0.01 and 0.0001). As for the monoaminergic neurotransmission, atrazine led to very few alterations on the dopamine and serotonin systems that were limited to the females (p < 0.05). Altogether, the results suggests that peripubertal exposure of atrazine cause behavioral and neurochemical alterations. More studies need to be conducted to fully understand the differences in atrazine's effects and its use should be considered carefully.

A Review on the Disruption of Novel Object Recognition Induced by Methamphetamine

Background

Methamphetamine (MA), is a widely abused synthetic psychostimulant that leads to irreversible brain damage manifested as cognitive impairments in humans and animals. The novel object recognition (NOR) task is a commonly used behavioral assay for the investigation of non-spatial memory in rodents. This test is based on the natural tendency of rodents to spend more time exploring a novel object than a familiar one. NOR test has been used in many studies investigating cognitive deficits caused by MA in rodents. The objective of the present study was to review neurobiological mechanisms that might be responsible for MA-induced NOR alterations.

Methods

A PubMed search showed 83 publications using novel object recognition and methamphetamine as keywords in the past 10 years.

Findings

The present study revealed different MA regimens cause recognition memory impairment in rodents. In addition, it was found that the main neurobiological mechanism involved in MA-induced recognition deficits is the dysfunction of monoaminergic systems.

Conclusion

NOR is a useful test to assess the cognitive functions following MA administration and evaluate the efficacy of new therapeutic agents in MA-addicted individuals.

The combined depletion of monoamines alters the effectiveness of subthalamic deep brain stimulation

Non-motor symptoms of Parkinson's disease are under-studied and therefore not well treated. Here, we investigated the role of combined depletions of dopamine, norepinephrine and/or serotonin in the manifestation of motor and non-motor deficits in the rat. Then, we studied the impact of these depletions on the efficacy of deep brain stimulation of the subthalamic nucleus (STN-DBS). We performed selective depletions of dopamine, norepinephrine and serotonin, and the behavioral effects of different combined depletions were investigated using the open field, the elevated plus maze and the forced swim test. Bilateral dopamine depletion alone induced locomotor deficits associated with anxiety and mild "depressive-like" behaviors. Although additional depletions of norepinephrine and/or serotonin did not potentiate locomotor and anxiety disorders, combined depletions of the three monoamines dramatically exacerbated "depressive-like" behavior. STN-DBS markedly reversed locomotor deficits and anxiety behavior in animals with bilateral dopamine depletion alone. However, these improvements were reduced or lost by the additional depletion of norepinephrine and/or serotonin, indicating that the depletion of these monoamines may interfere with the antiparkinsonian efficacy of STN-DBS. Furthermore, our results showed that acute STN-DBS improved "depressive-like" disorder in animals with bilateral depletion of dopamine and also in animals with combined depletions of the three monoamines, which induced severe immobility in the forced swim test. Our data highlight the key role of monoamine depletions in the pathophysiology of anxiety and depressive-like disorders and provide the first evidence of their negative consequences on the efficacy of STN-DBS upon the motor and anxiety disorders in the context of Parkinson's disease.