clozapine-n-oxide and Parkinsonian-Disorders

PD is a common neurodegenerative disease primarily affecting the cortico-basal ganglia loop.. To investigate whether chemogenetic-mediated neuromodulation of various nuclei and pathways can counterbalance basal ganglia network abnormalities and improve motor disability in experimental PD.. Experimental PD was induced by stereotactic injection of 6-OHDA to the medial forebrain bundle. Designer receptors exclusively activated by designer drugs were expressed in different basal ganglia nuclei by stereotactic injections of adeno-associated viral vectors. We compared motor performance, monitored by the open-field and rotarod tests, after random and blinded application of either normal saline or the synthetic receptor activator, clozapine-N-oxide.. Motor performance, as measured by movement velocity, rotations, and rotarod scores, were significantly improved in PD mice by enhancing the activity of the GPe with Gq custom receptors and by reducing basal ganglia output activity, targeting the output nuclei GPi and SNr with Gi custom receptors.. Our findings support the hypothesis that enhanced inhibitory output activity of the basal ganglia complex underlie motor signs in PD, and point to the therapeutic potential of chemogenetic based treatments in PD patients. © 2018 International Parkinson and Movement Disorder Society.

Topics: Animals; Basal Ganglia; Clozapine; Genetic Vectors; Male; Medial Forebrain Bundle; Mice; Motor Activity; Neurons; Oxidopamine; Parkinsonian Disorders; Rotarod Performance Test

Transplantation of DA neurons is actively pursued as a restorative therapy in Parkinson's disease (PD). Pioneering clinical trials using transplants of fetal DA neuroblasts have given promising results, although a number of patients have developed graft-induced dyskinesias (GIDs), and the mechanism underlying this troublesome side effect is still unknown. Here we have used a new model where the activity of the transplanted DA neurons can be selectively modulated using a bimodal chemogenetic (DREADD) approach, allowing either enhancement or reduction of the therapeutic effect. We show that exclusive activation of a cAMP-linked (Gs-coupled) DREADD or serotonin 5-HT6 receptor, located on the grafted DA neurons, is sufficient to induce GIDs. These findings establish a mechanistic link between the 5-HT6 receptor, intracellular cAMP, and GIDs in transplanted PD patients. This effect is thought to be mediated through counteraction of the D2 autoreceptor feedback inhibition, resulting in a dysplastic DA release from the transplant.

Topics: Animals; Clozapine; Cyclic AMP; Diterpenes; Diterpenes, Clerodane; Dopamine; Dopaminergic Neurons; Dyskinesia, Drug-Induced; Ethylamines; Female; Fetal Tissue Transplantation; Gene Knock-In Techniques; Humans; Indoles; Oxidopamine; Parkinsonian Disorders; Postoperative Complications; Rats; Receptors, Serotonin

Direct lineage reprogramming through genetic-based strategies enables the conversion of differentiated somatic cells into functional neurons and distinct neuronal subtypes. Induced dopaminergic (iDA) neurons can be generated by direct conversion of skin fibroblasts; however, their in vivo phenotypic and functional properties remain incompletely understood, leaving their impact on Parkinson's disease (PD) cell therapy and modeling uncertain. Here, we determined that iDA neurons retain a transgene-independent stable phenotype in culture and in animal models. Furthermore, transplanted iDA neurons functionally integrated into host neuronal tissue, exhibiting electrically excitable membranes, synaptic currents, dopamine release, and substantial reduction of motor symptoms in a PD animal model. Neuronal cell replacement approaches will benefit from a system that allows the activity of transplanted neurons to be controlled remotely and enables modulation depending on the physiological needs of the recipient; therefore, we adapted a DREADD (designer receptor exclusively activated by designer drug) technology for remote and real-time control of grafted iDA neuronal activity in living animals. Remote DREADD-dependent iDA neuron activation markedly enhanced the beneficial effects in transplanted PD animals. These data suggest that iDA neurons have therapeutic potential as a cell replacement approach for PD and highlight the applicability of pharmacogenetics for enhancing cellular signaling in reprogrammed cell-based approaches.

Topics: Animals; Brain; Cell Transdifferentiation; Clozapine; Designer Drugs; Disease Models, Animal; Dopamine; Dopaminergic Neurons; Electrophysiological Phenomena; Female; Humans; Male; Mice; Mice, Knockout; Parkinsonian Disorders; Rats; Rats, Transgenic