Abstract
The paraventricular nucleus of the hypothalamus (PVN) is required for full expression of cardiorespiratory responses evoked by peripheral chemoreflex stimulation. However, the efferent pathways from the PVN that contribute to chemoreflex responses are not fully understood. We have previously shown that hypoxia activates (Fos‐immunoreactivity; IR) PVN neurons that project to the nTS, and a large proportion of these neurons are CRH‐IR. Activation of CRF2 receptors (CRFR2) in the nTS elicits cardiovascular responses, and thus we considered that CRH PVN neurons may influence nTS neuronal activity and cardiorespiratory effects of chemoreflex activation through binding of CRH to CRFR2s. Immunohistochemistry was performed to determine the distribution of CRFR2 in the nTS. CRFR2‐IR was not identified in neurons or glia but was localized in fibers throughout the caudal, postremal and rostral nTS. CRFR2 formed close appositions on dendrites (displaying MAP2‐IR) of nTS catecholaminergic (tyrosine hydroxylase; TH‐IR) neurons and a portion of CRFR2 was colocalized with the synaptic vesicle protein Synaptophysin (Syn). An AAV viral vector expressing mCherry under the promoter CAMKII was microinjected into the PVN and mCherry containing fibers in nTS were evaluated. Terminals in the nTS originating from the PVN (mCherry) also exhibited colabeling with Syn and appeared to make close appositions on TH‐IR nTS neurons. Interestingly, CRFR2‐labeled fibers were colocalized extensively with oxytocin‐IR that also exhibited Syn‐IR. These results suggest that CRH, likely from the PVN, may bind to presynaptic CRFR2s located on oxytocin‐containing fibers to modulate the activity of catecholaminergic nTS neurons and influence cardiorespiratory regulation.Support or Funding InformationNIH RO1 HL98602
Published Version
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