Tonic and phasic changes in anteromedial globus pallidus activity in Tourette syndrome.

BACKGROUND: Tourette syndrome is a hyperkinetic neurodevelopmental disorder characterized by tics. OBJECTIVE: Assess the neuronal changes in the associative/limbic GP associated with Tourette syndrome. METHODS: Neurophysiological recordings were performed from the anterior (associative/limbic) GPe and GPi of 8 awake patients during DBS electrode implantation surgeries. RESULTS: The baseline firing rate of the neurons was low in a state-dependent manner in both segments of the GP. Tic-dependent transient rate changes were found in the activity of individual neurons of both segments around the time of the tic. Neither oscillatory activity of individual neurons nor correlations in their interactions were observed. CONCLUSIONS: The results demonstrate the involvement of the associative/limbic pathway in the underlying pathophysiology of Tourette syndrome and point to tonic and phasic modulations of basal ganglia output as a key mechanisms underlying the abnormal state of the disorder and the expression of individual tics, respectively. © 2017 International Parkinson and Movement Disorder Society.

Transgenic Rat Models of Huntington's Disease.

Several animal models for Huntington's disease (HD) have been created in order to investigate mechanisms of disease, and to evaluate the potency of novel therapies. Here, we describe the characteristics of the two transgenic rat models: transgenic rat model of HD (fragment model) and the Bacterial Artificial Chromosome HD model (full-length model). We discuss their genetic, behavioural, neuropathological and neurophysiological features.

An experimental model for Huntington's chorea?

Clinically, Huntington's disease (HD) is well known for the predominant motor symptom chorea, which is a hyperkinetic motor disorder. The only experimental model currently described in the literature, as far as we are aware of, exhibiting hyperkinetic movements is the transgenic rat model of HD. We assessed and characterized these hyperkinetic movements in detail and investigated the effect of tetrabenazine (TBZ) treatment. TBZ is an effective drug in the treatment of chorea in HD patients. Our results showed that the hyperkinetic movements fulfilled the clinical-behavioral criteria of a choreiform movement. Administration of TBZ reduced the number of these hyperkinetic movements substantially. These findings suggest that the hyperkinetic movements observed in this animal model can be considered as a choreiform movement disorder. This makes these animals unique and provides opportunities for chorea-research.

Haloperidol-induced changes in neuronal activity in the striatum of the freely moving rat.

The striatum is the main input structure of the basal ganglia, integrating input from the cerebral cortex and the thalamus, which is modulated by midbrain dopaminergic input. Dopamine modulators, including agonists and antagonists, are widely used to relieve motor and psychiatric symptoms in a variety of pathological conditions. Haloperidol, a dopamine D2 antagonist, is commonly used in multiple psychiatric conditions and motor abnormalities. This article reports the effects of haloperidol on the activity of three major striatal subpopulations: medium spiny neurons (MSNs), fast spiking interneurons (FSIs), and tonically active neurons (TANs). We implanted multi-wire electrode arrays in the rat dorsal striatum and recorded the activity of multiple single units in freely moving animals before and after systemic haloperidol injection. Haloperidol decreased the firing rate of FSIs and MSNs while increasing their tendency to fire in an oscillatory manner in the high voltage spindle (HVS) frequency range of 7-9 Hz. Haloperidol led to an increased firing rate of TANs but did not affect their non-oscillatory firing pattern and their typical correlated firing activity. Our results suggest that dopamine plays a key role in tuning both single unit activity and the interactions within and between different subpopulations in the striatum in a differential manner. These findings highlight the heterogeneous striatal effects of tonic dopamine regulation via D2 receptors which potentially enable the treatment of diverse pathological states associated with basal ganglia dysfunction.

Lessons learned from the transgenic Huntington's disease rats.

Huntington's disease (HD) is a fatal inherited disorder leading to selective neurodegeneration and neuropsychiatric symptoms. Currently, there is no treatment to slow down or to stop the disease. There is also no therapy to effectively reduce the symptoms. In the investigation of novel therapies, different animal models of Huntington's disease, varying from insects to nonhuman primates, have been created and used. Few years ago, the first transgenic rat model of HD, carrying a truncated huntingtin cDNA fragment with 51 CAG repeats under control of the native rat huntingtin promoter, was introduced. We have been using this animal model in our research and review here our experience with the behavioural, neurophysiological, and histopathological phenotype of the transgenic Huntington's disease rats with relevant literature.

Motor and non-motor behaviour in experimental Huntington's disease.

In this study, we investigated motor and non-motor behaviour in the transgenic rat model of Huntington's disease (tgHD). In particular, we were interested in the development and changes of motor and non-motor features (anxiety, motivation and hedonia) of disease over time and their interactions. We found tgHD animals to be hyperkinetic in the open field test compared to their wild-type littermates at all ages tested, which was accompanied by reduced anxiety-like behaviour in the open field test and the elevated zero maze, but not in the home cage emergence test. No major changes were found in hedonia (sucrose intake test) and motivation for food (food intake test). Our data suggest that hyperkinetic features and reduced-anxiety in the tgHD rats are associated behaviours and are seen in the earlier stages of the disease.

Memory deficits in the transgenic rat model of Huntington's disease.

Memory deficits are common in patients with Huntington's disease (HD) and have a substantial impact on the quality of life of patients and their relatives. A good model resembling the human memory deficits is needed for research purposes. In this study we investigated the memory function of the transgenic rat model of Huntington's disease (tgHD) in the object location (OLT) and the object recognition task (ORT). Several studies have shown that the recent developed tgHD rat model resembles the human phenotype of HD. Impairments of spatial and object recognition memory in the OLT and ORT, however, have to our knowledge not yet been reported in this transgenic model. Our findings show that in both early and late stages of the disease the tgHD rats have clear deficits for both visuospatial and visual object memory. Since HD patients are known to be impaired in both types of memory, these results confirm the validity of this tgHD rat as a model for the human HD phenotype.