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Characterization of Tyrosine Hydroxylase-Positive Neurons Projections from the Paraventricular Nucleus of Hypothalamus to Hindbrain Autonomic Regulatory Centers
AdvisorFeng Earley , Yumei
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Hypothalamus is a key brain region for cardiovascular, behavioral, and metabolic regulation that contains complex type of excitatory or inhibitory neurons. Tyrosine hydroxylase (TH)-positive neurons in the hypothalamus plays important role in cardiometabolic regulation; however, the anatomical projections of TH neurons in the paraventricular nucleus hypothalamus (PVN) to key parasympathetic and sympathetic premotor nuclei in medulla oblongata, including the nucleus tractus solitarius (NTS), dorsal motor nucleus of the vagus (DMV), and rostral ventrolateral medulla (RVLM), remains undefined. This study aims to characterize the projections from THPVN neuron to ventral preautonomic regulating centers. To achieve our goal, Cre recombinase-dependent TIT2L-eGFP reporter mice were microinjected with adeno-associated virus encoding the Cre recombinase driven by rat TH promoter (AAV2-rTHP-Cre, 6.8 x 1011 gc) into the PVN using a stereotaxic apparatus. One month after injection, mice were transcardially perfused and brain tissues were processed for imaging. First, the site of injection was confirmed by the presence of GFP+ cells in the PVN. Second, GFP were visualized in different areas to identify the projections. The AAV2-rTHP-Cre induced a robust expression of GFP in PVN neuronal cell bodies but not in other brain regions. More interesting, we found dense projections in the NTS and some projections to the DMV and RVLM. Surprisingly, there was also dense projects into the and median eminence (ME) that regulates neural hormones release. In sum, the THPVN neuron projects anatomically to the autonomic and neurosecretory regions of brain and may modulate the cardiometabolic activity through these projections.