Biology subjects

Whelan, P.

Publications and source records attributed to Whelan, P..

3 recordsLinked to original sources

bioRxiv2023

Restoration of locomotor function following stimulation of the A13 region in Parkinson's mouse models

Parkinsons disease (PD) is characterized by extensive motor and non-motor dysfunction, including gait disturbance, which is difficult to treat effectively. This study explores the therapeutic potential of targeting the A13 region, a heterogeneous region of the medial zona incerta (mZI) containing dopaminergic, GABAergic, and glutamatergic neurons that has shown relative preservation in PD models. The A13 is identified to project to the mesencephalic locomotor region (MLR), with a subpopulation of cells displaying activity correlating to movement speed, suggesting its role in locomotion. We show that photoactivation of this A13 region can alleviate bradykinesia and akinetic features, while increasing turning in a mouse model of PD. These effects combine disease-specific rescue of function with a possible gain of function. We identified areas of preservation and plasticity within the A13 region using whole-brain imaging. Our findings suggest a global remodeling of afferent and efferent projections of the A13 region, highlighting the zona incertas role as a crucial hub for the rapid selection of motor function. The study unveils the significant pro-locomotor effects of the A13 region and suggests its promising potential as a therapeutic target for PD-related gait dysfunction. SIGNIFICANCE STATEMENTThis work examines the function of the A13 region in locomotion, an area with direct connectivity to locomotor regions in the brainstem. A13 stimulation can restore locomotor function and improve bradykinesia in a PD mouse model.

neuroscience↗

bioRxiv2021

Substantia nigra degradation results in widespread changes in medial zona incerta afferent and efferent connectomics

Parkinsons disease (PD) is a complex disease affecting many facets of movement, especially gait abnormalities such as shuffling and freezing of gait. The nigrostriatal pathways of the basal ganglia are traditionally targeted by existing therapies; however, other pathways may be more relevant to gait, such as the pedunculopontine nucleus and the zona incerta (ZI). The A13 nucleus may be such a target as it has emerged as an area of interest in dopamine motor function. Yet, this area remains understudied compared to other dopamine nuclei, especially in animal models of PD. In 6-OHDA mice, we found a reduction in locomotion in the open field and gait dysfunction during treadmill tests. Medial ZI dopamine cells, containing the A13 nucleus, were preserved following 6-OHDA, in contrast to a marked reduction in substantia nigra pars compacta (SNc) neurons. There was extensive remodelling of the A13 afferent and efferent connectome following nigrostriatal lesions. Afferent input patterns displayed a marked reduction in cross-correlation across brain regions in 6-OHDA mice, while efferent projections showed an increase. In a human PD patient with advanced gait dysfunction we found that the A13 nucleus was preserved, suggesting that remodelling could also occur in humans. This work points to the A13 region as a potential therapeutic target in PD. Significance StatementRecently it was found that the medial zona incerta projects to the cuneiform nucleus suggesting a parallel dopaminergic projection onto motor regions. Here we investigated the connectome of the A13 region and examined the afferent and efferent projections in normal mice and mice with a unilateral Parkinsonian mouse model. We found that the connectome was reconfigured following nigrostriatal degeneration. This work provides a comprehensive insight into the plasticity in a dopaminergic-rich area of the zona incerta in PD injury models.

neuroscience↗

bioRxiv2019

Dopaminergic control of postnatal mammalian spinal network function is predominantly inhibitory.

Dopamine is well known to regulate movement through the differential control of direct and indirect pathways in the striatum that express D1 and D2 receptors respectively. The spinal cord also expresses all dopamine receptors however; how the specific receptors regulate spinal network output in mammals is poorly understood. We explore the receptor-specific mechanisms that underlie dopaminergic control of spinal network output of neonatal mice during changes in spinal network excitability. During spontaneous activity, which is a characteristic of developing spinal networks operating in a low excitability state, we found that dopamine is primarily inhibitory. We uncover an excitatory D1-mediated effect of dopamine on motoneurons and network output that also involves co-activation with D2 receptors. Critically, these excitatory actions require higher concentrations of dopamine; however, analysis of dopamine concentrations of neonates indicates that endogenous levels of spinal dopamine are low. Because endogenous levels of spinal dopamine are low, this excitatory dopaminergic pathway is likely physiologically-silent at this stage in development. In contrast, the inhibitory effect of dopamine, at low physiological concentrations is mediated by parallel activation of D2, D3, D4 and 2 receptors which is reproduced when endogenous dopamine levels are increased by blocking dopamine reuptake and metabolism. We provide evidence in support of dedicated spinal network components that are controlled by excitatory D1 and inhibitory D2 receptors that is reminiscent of the classic dopaminergic indirect and direct pathway within the striatum. These results indicate that network state is an important factor that dictates receptor-specific and therefore dose-dependent control of neuromodulators on spinal network output and advances our understanding of how neuromodulators regulate neural networks under dynamically changing excitability.\n\nSignificance statementMonoaminergic neuromodulation of neural networks is dependent not only on target receptors but also on network state. We studied the concentration-dependent control of spinal networks of the neonatal mouse, in vitro, during a low excitability state characterized by spontaneous network activity. Spontaneous activity is an essential element for the development of networks. Under these conditions, we defined converging receptor and cellular mechanisms that contribute to the diverse, concentration-dependent control of spinal motor networks by dopamine, in vitro. These experiments advance understanding of how monoamines modulate neuronal networks under dynamically changing excitability conditions and provide evidence of dedicated D1 and D2 regulated network components in the spinal cord that are consistent with those reported in the striatum.

neuroscience↗