Pain hypersensitivity in a pharmacological mouse model of attention-deficit/hyperactivity disorder.

Clinical evidence suggests that pain hypersensitivity develops in patients with attention-deficit/hyperactivity disorder (ADHD). However, the mechanisms and neural circuits involved in these interactions remain unknown because of the paucity of studies in animal models. We previously validated a mouse model of ADHD obtained by neonatal 6-hydroxydopamine (6-OHDA) injection. Here, we have demonstrated that 6-OHDA mice exhibit a marked sensitization to thermal and mechanical stimuli, suggesting that phenotypes associated with ADHD include increased nociception. Moreover, sensitization to pathological inflammatory stimulus is amplified in 6-OHDA mice as compared to shams. In this ADHD model, spinal dorsal horn neuron hyperexcitability was observed. Furthermore, ADHD-related hyperactivity and anxiety, but not inattention and impulsivity, are worsened in persistent inflammatory conditions. By combining in vivo electrophysiology, optogenetics, and behavioral analyses, we demonstrated that anterior cingulate cortex (ACC) hyperactivity alters the ACC-posterior insula circuit and triggers changes in spinal networks that underlie nociceptive sensitization. Altogether, our results point to shared mechanisms underlying the comorbidity between ADHD and nociceptive sensitization. This interaction reinforces nociceptive sensitization and hyperactivity, suggesting that overlapping ACC circuits may be targeted to develop better treatments.

Antiseizure effects of Anacyclus pyrethrum in socially isolated rats with and without a positive handling strategy.

OBJECTIVE: Aqueous extract of Anacyclus pyrethrum (AEAPR) is used in traditional medicine to treat epilepsy, but whether it has antiseizure properties has not been established. Because extracts of the plant have antioxidant properties, we hypothesized that it may be particularly potent in conditions associated with oxidative stress, in particular social isolation. METHODS: We addressed these objectives in the pilocarpine experimental model of epilepsy using socially isolated rats maintaining contacts with (handled) and without (unhandled) positive handling strategy. Both groups were further divided into treated (AEAPR was added to the drinking water) and untreated groups. Continuous (24/7) electroencephalography (EEG) recordings started in the sixth week after status epilepticus (SE) with a predrug control period of 3 weeks, followed by 3 weeks of daily treatment with AEAPR or water, and finally a postdrug control period of 3 weeks. At the end of the experimental procedure, we measured lipid peroxidation, superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase activities in the hippocampus to assess oxidative stress. RESULTS: A. pyrethrum treatment significantly reduced seizure frequency by 51% and 57%, duration by 30% and 33%, and severity by 31% and 26% in isolated handled and unhandled rats, respectively. The beneficial effects on seizures were still present 3 weeks after the end of the treatment. The treatment reduced lipid peroxidation as well as SOD, GPx, and catalase activities. SIGNIFICANCE: We conclude that A. pyrethrum has antiseizure and antioxidant properties, even in social isolation conditions.

PIEZO2-dependent rapid pain system in humans and mice.

The PIEZO2 ion channel is critical for transducing light touch into neural signals but is not considered necessary for transducing acute pain in humans. Here, we discovered an exception - a form of mechanical pain evoked by hair pulling. Based on observations in a rare group of individuals with PIEZO2 deficiency syndrome, we demonstrated that hair-pull pain is dependent on PIEZO2 transduction. Studies in control participants showed that hair-pull pain triggered a distinct nocifensive response, including a nociceptive reflex. Observations in rare Aß deafferented individuals and nerve conduction block studies in control participants revealed that hair-pull pain perception is dependent on Aß input. Single-unit axonal recordings revealed that a class of cooling-responsive myelinated nociceptors in human skin is selectively tuned to painful hair-pull stimuli. Further, we pharmacologically mapped these nociceptors to a specific transcriptomic class. Finally, using functional imaging in mice, we demonstrated that in a homologous nociceptor, Piezo2 is necessary for high-sensitivity, robust activation by hair-pull stimuli. Together, we have demonstrated that hair-pulling evokes a distinct type of pain with conserved behavioral, neural, and molecular features across humans and mice.

Neonatal 6-OHDA Lesion Model in Mouse Induces Cognitive Dysfunctions of Attention-Deficit/Hyperactivity Disorder (ADHD) During Young Age.

Attention-deficit/hyperactivity disorder (ADHD) is a syndrome characterized by impaired attention, impulsivity and hyperactivity in children. These symptoms are often maintained in adults. During adolescence, prefrontal cortex develops connectivity with other brain regions to engage executive functions such as, latent inhibition, attention and inhibitory control. In our previous work, we demonstrated the validity of the neonatal 6-Hydroxydopamine (6-OHDA) mouse model, a classical neurodevelopmental model mimicking major symptoms of the human ADHD pathology. In order to evaluate pathological forms of executive functions and impulsive behavior in 6-OHDA mice during young age, we first tested latent inhibition (LI) after weaning, and then we evaluated the impulsive behavior using a cliff avoidance reaction test. Our results demonstrated that 6-OHDA mice showed disruption in latent inhibition, suggesting a deficit in selective attention, and displayed repetitive peering-down behavior, indicating a maladaptive impulsive behavior. Subsequently, to assess impulsivity and attention in young mice, we performed a modified 5-choice serial reaction time task test (5-CSRTT), optimizing the degree of food restriction for young animals and shortening the training duration. This test allowed us to demonstrate a deficit in inhibitory control and a loss of accuracy of 6-OHDA mice in the 5-CSRTT. In conclusion, we demonstrated that the 6-OHDA mouse model reproduces human symptoms of ADHD in childhood and early adulthood periods, as seen in human. Taken together, the 6-OHDA mouse model will be useful alongside other animal models to understand the neurobiological mechanisms underlying complex, heterogeneous neurological disorders.

Anticonvulsive and neuroprotective effects of aqueous and methanolic extracts of Anacyclus pyrethrum root in kainic acid-induced-status epilepticus in mice.

PURPOSE: Epilepsy is a chronic neurological disorder characterized by spontaneous and recurrent seizures. The currently available synthetic antiepileptic drugs have a limited efficacy and are associated with a wide range of side effects. In Ayurveda, Anacyclus pyrethrum root (APR) has been used as a traditional antiepileptic remedy. The aim of the present study is to evaluate the anticonvulsive and neuroprotective effects of aqueous and methanol extracts of Anacyclus pyrethrum root (AEAPR and MEAPR) on experimental model of status epilepticus (SE). METHODS: Twenty four male mice were divided into four groups. The control and KA groups had free access to tap water for 5 days before the intraperitoneal injection of distillated water or kainic acid (KA; 30 mg/kg), respectively. In the treated groups, mice received extracts solutions MEAPR and AEAPR in drinking water at the concentration of 5 g/l for 5 days. At the fifth day, animals received intraperitoneal injection of KA. The behavioral changes latency of seizures, the number of wet dog shakes (WDS) and the mortality were observed over 6 h. Thereafter, the mice were sacrificed for immunohistochemical studies. RESULTS: Pretreatment with MEAPR and AEAPR decreases significantly the frequency of WDS (32.5% and 43.9%, p < 0.01; respectively), and increases considerably the latent period (77.9% and 91.9%, p<0.01; respectively) between the injection of the KA and the appearance of the SE as compared to the KA group. The duration and severity of seizure in the MEAPR or AEAPR-pretreated groups were significantly lower (p < 0.01 and p < 0.05 or p < 0.01; respectively) than those in the KA group. These behavioral results were confirmed by the immunohistochemical study at the level of the hippocampus, in which the c-FOS and GFAP expression of both MEAPR and AEAPR-treated animals largely reduced (p < 0.001) the number of labelled cells with respect to the group, which received the KA alone. CONCLUSION: Our results showed that the MEAPR and AEAPR have anticonvulsive effect and putative neuroprotective effect against seizures induced by KA. Further studies are required to identify its active ingredients responsible for the observed effects.

Neonatal 6-OHDA lesion model in mouse induces Attention-Deficit/ Hyperactivity Disorder (ADHD)-like behaviour.

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by impaired attention, impulsivity and hyperactivity. The "neonatal 6-hydroxydopamine" (6-OHDA) lesion is a commonly used model of ADHD in rat. However, a comprehensive assessment of ADHD-like symptoms is still missing, and data in mouse remain largely unavailable. Our aim was to analyse symptoms of ADHD in the mouse neonatal 6-OHDA model. 6-OHDA mice exhibited the major ADHD-like symptoms, i.e. hyperactivity (open field), attention deficit and impulsivity (five-choice serial reaction time task). Further, the model revealed discrete co-existing symptoms, i.e. anxiety-like (elevated plus maze test) and antisocial (social interaction) behaviours and decreased cognitive functioning (novel object recognition). The efficacy of methylphenidate, a classical psychostimulant used in the treatment of ADHD, was also evaluated. A histological analysis further supports the model validity by indicating dopamine depletion, changes in cortical thickness and abnormalities in anterior cingulate cortex neurons. A principal component analysis of the behaviour profile confirms that the 6-OHDA mouse model displayed good face and predictive validity. We conclude that neonatal dopamine depletion results in behavioural and morphological changes similar to those seen in patients and therefore could be used as a model for studying ADHD pathophysiological mechanisms and identifying therapeutic targets.

Anti-inflammatory, Antinociceptive, and Antioxidant Activities of Methanol and Aqueous Extracts of Anacyclus pyrethrum Roots.

Anacyclus pyrethrum (L.) is a plant widely used in Moroccan traditional medicine to treat inflammatory and painful diseases. The objective of the present study was to evaluate the antinociceptive, anti-inflammatory and antioxidant activities of aqueous and methanol extracts of Anacyclus pyrethrum roots (AEAPR and MEAPR). The anti-inflammatory effect of AEAPR and MEAPR was determined in xylene-induced ear edema and Complete Freund's Adjuvant (CFA)-induced paw edema. The antinociceptive activity of AEAPR and MEAPR (125, 250, and 500 mg/kg) administered by gavage was examined in mice by using acetic acid-induced writhing, hot plate, and formalin tests, and the mechanical allodynia were assessed in CFA-induced paw edema. In addition, the in vitro antioxidant activities of the extracts were determined by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, ferric reducing power and ß-carotene-linoleic acid assay systems. AEAPR and MEAPR produced significant reductions in CFA-induced paw edema and xylene-induced ear edema. A single oral administration of these extracts at 250 and 500 mg/kg significantly reduced mechanical hypersensitivity induced by CFA, which had begun 1 h 30 after the treatment, and was maintained till 7 h. Chronic treatment with both extracts significantly reduced mechanical hypersensitivity in persistent pain conditions induced by CFA. Acute pretreatment with AEAPR or MEAPR at high dose caused a significant decrease in the number of abdominal writhes induced by acetic acid injection (52.2 and 56.7%, respectively), a marked increase of the paw withdrawal latency in the hot plate test, and also a significant inhibition of both phases of the formalin test. This antinociceptive effect was partially reversed by naloxone pretreatment in the hot plate and formalin tests. Additionally, a significant scavenging activity in DPPH, reducing power and protection capacity of ß-carotene was observed in testing antioxidant assays. The present study suggests that AEAPR and MEAPR possess potent anti-inflammatory, antinociceptive and antioxidant effects which could be related to the presence of alkaloids and phenols in the plant. In addition, the antinociceptive effect of APR extracts seems to partly involve the opioid system. Taken together, these results suggest that Anacylcus pyrethrum may indeed be useful in the treatment of pain and inflammatory disorders in humans.