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Chemical Stimulation of the Arterial Chemoreflex Activates Neuroendocrine and Pre‐sympathetic Corticotropin Releasing Hormone (CRH) Neurons in the Paraventricular Nucleus of the Hypothalamus (PVN)
Author(s) -
Coldren K.,
Kline David,
Hasser Eileen,
Heesch Cheryl
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.653.6
Subject(s) - medicine , endocrinology , parvocellular cell , hypothalamus , corticotropin releasing hormone , chemistry , stimulation , sympathetic nervous system , rostral ventrolateral medulla , biology , central nervous system , blood pressure , medulla oblongata
Acute hypoxia (AH) increases corticosteroid secretion through activation of the arterial chemoreflex central pathway including the PVN. Previously we found that CRH was present in pre‐sympathetic neurons, but, although AH (10% O 2 , 2 hrs) activated CRH‐IR cells (~14%), pre‐sympathetic neurons in the PVN were not activated. We hypothesized that, compared to neuroendocrine cells, a more potent chemoreflex stimulus might be required to activate pre‐sympathetic PVN neurons. Conscious rats received repeated i.v. sodium cyanide (NaCN) or saline (Sal); 10 injections once every 3 minutes, followed by immunohistochemical evaluation of Fos‐ (index of activation) and CRH‐IR. Pre‐sympathetic cells in the PVN were identified by prior retrograde tracer injections into the RVLM & IML. More CRH cells were activated by NaCN (CRH+Fos; 34±5%) compared to Sal treated rats (9±2%), with a substantial portion located in the medial parvocellular region (presumed neuroendocrine). NaCN also activated RVLM (11±2 vs 6±1%) and IML projecting cells (13±2 vs 6±1%). Of the activated pre‐sympathetic cells in NaCN treated rats, 83±4% of RVLM and 80±4% of IML projecting cells were CRH‐IR. Thus, activation of the chemoreflex with NaCN excites both neuroendocrine (medial parvocellular) and pre‐sympathetic CRH neurons in the PVN. Compared to AH, NaCN treatment activated more CRH (34±5 vs 15±3%) and IML projecting cells (13±2 vs 5±0.1%). Future experiments will evaluate differential regulation of CRH‐neuroendocrine vs CRH‐pre‐sympathetic cells in the PVN. [NIH HL 98602]