Neuroscience. 1999;88(3):949-57
Pyner S, Coote JH.
http://www.sciencedirect.com/science/article/pii/S0306452298002553
As we know both RVLM and PVN are important brain areas which are known to be involved in the regulation of cardiovascular activity. The purpose of this study was to determine whether paraventricular axons project to the rostral ventrolateral medulla and whether they are closely apposed to reticulospinal neurons in this region. In this study they have used anterograde tracing to see whether neurons in the PVN send efferent fibers that terminate on or near the retrogradely labelled RVLM spinally projecting neurons.Biotin dextran amine (BDA, Molecular Probes 10,000 mol.wt 10% in 10 mM phosphate buffer pH 7.25) was iontophoretically deposited in and around the PVN over a period of 20 min. The injection sites in the PVN covered a wide range of areas around the PVN. BDA labelled axons were found in the RVLM as a result of each of these injections.After 10–14 days animals were re-anaesthetized and 1 μl of 4% wheatgerm agglutinin–horseradish peroxidase (WGA–HRP) pressure injected into spinal segment T2 after stabilizing the vertebral column with a clamp on T2 spine. BDA filled axons located in the RVLM and originating from the PVN injections sites were thin in appearance and purple in colour compared to the black/brown WGA–HRP labelled RVLM neurons.The present study using anterograde and retrograde tracing methods has identified axons originating from the PVN that intermingle with RVLM reticulospinal neurons. Many of these PVN axons have terminal varicosities that are either apposed to or closely associated with RVLM reticulospinal neuronal cell bodies and dendrites. This article concludes that axons originating in the PVN terminate close to spinally projecting RVLM neurons which are assumed to terminate on sympathetic preganglionic neurons(SPN). So the PVN could involve in the cardiovascular activity through its descending projection to the SPN.
Madhan
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