Browsing by Author "Grams, Joseph R"

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    Hypothalamic dopamine neurons project to brainstem regions related to movement
    (2022-06-22) Grams, Joseph R; Whelan, Patrick J.; Cluff, Tyler; Wilson, Richard
    Locomotion is a complex behaviour resulting from interactions between the brain and spinal cord. Dopamine modulates locomotion via ascending projections to the basal ganglia and descending projections to the mesencephalic locomotor region (MLR). The MLR is a region in the brainstem known to initiate and control locomotion. Motor commands from supraspinal structures are relayed to the spinal cord via the medullary reticular formation (MRF). However, it remains uncertain if dopamine neurons also innervate regions of the MRF known to influence locomotor activity. Using a retrograde viral tracing approach, I identified a discrete dopaminergic pathway that extends from the A11 region of the posterior hypothalamus to locomotor regions of the MRF. Furthermore, using an anterograde viral tracing technique, I found that dopamine neurons of the A11 region project throughout the rostrocaudal extent of the MRF and terminate predominantly ipsilaterally. Contrastingly, using immunohistochemistry, I show that neurons in the MRF are devoid of D1 receptors. Lastly, using the genetically encoded dopamine sensor dLight1.2 and fibre photometry, I provide evidence of altered dopamine transients during locomotor activity. Together, these results suggest that dopaminergic innervation of the MRF is sparse and originates primarily from the A11 region of the posterior hypothalamus. Further investigation is required to determine the functional contributions to neural circuits in the MRF.