Authors
Abstract
Background and purpose: Sympatho-excitatory neurons which originate from Rostral Ventrolateral Medulla (RVLM) and project to spinal cord are necessary for the maintenance of resting sympathetic tone and integration of cardiovascular reflexes. Also it is known that catecholamines substance P and somatostatin are involved in blood pressure modulation in the brain stem. The aim of this study was answering to the question: Is somatostatin 2A receptor (SST2A) expressed in medullary C1 neurons which have preprotachykinin A (PPT-A) mRNA and are projected to spinal cord? Methods and materials: This study was done on 12 male Sprague-Dawley rats. We used a complex of techniques such as retrograde labeling of spinally projecting neurons by injection of Cholera Toxin Beta (CTB) unit In situ Hybridization (ISH) and Immunohistochemistry to identify PPT-A mRNA and SST2A receptor expression in C1 neurons of RVLM. For data deh1ion mean ± SEM as well as percentage were used. Results: Most spinally projecting neurons in RVLM (CTB+) are C1 neurons i.e. they have Tyrosin Hydroxylase enzyme (TH+). These neurons contain PPT-A mRNA or SST2A receptors but no neurons were observed with the expression of both PPT-A mRNA and SST2A receptor. Conclusion: It seems that medulla C1 neurons which project to spinal cord and express PPT-A mRNA or SST2A receptor are two separate neuron types. They may have different modulatory effects on cardiovascular reflexes.
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