Premium
Expression of adrenergic alpha 1 receptor subtypes in magnocellular, pre‐autonomic and medial parvocellular regions of the paraventricular nucleus of the hypothalamus (PVN): Effects of acute intermittent hypoxia
Author(s) -
Heesch Cheryl Miller,
Coldren Kevin Max,
Barr Stacy
Publication year - 2017
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.31.1_supplement.867.8
Subject(s) - parvocellular cell , endocrinology , medicine , hypothalamus , magnocellular cell , biology , supraoptic nucleus , vasopressin , adrenergic receptor , receptor , nucleus , chemistry , neuroscience
Catecholaminergic inputs to magnocellular, pre‐autonomic, and medial parvocellular neuroendocrine cells in the PVN may participate in activation of these neurons during chemoreflex stimulation. Current experiments evaluated the effects of acute intermittent hypoxia (AIH, 3 min 10% O 2 , separated by 5 min) on regional expression of alpha1 adrenergic receptor subtypes within the PVN. Spinally projecting PVN neurons were pre‐labeled in rats by prior IML injections of Fluorogold (2%,180 nl bilateral) to aid in visual identification of pre‐autonomic regions of the PVN. Conscious rats were exposed to AIH, while normoxic control rats (N) were exposed to changes in gas flow over the same times, but O 2 concentration remained at 21%. One hour later, rats were deeply anesthetized, brains were removed, and the forebrains sectioned (10 μm) on a cryostat. Laser Capture Microscopy (LCM) was used to capture magnocellular, pre‐autonomic and medial parvocellular neurons in the PVN. RNA was isolated, cDNA synthesized and, using target specific primers, expression of mRNA for alpha 1 adrenergic receptor subtypes, 1a, 1b, and 1d and the reference gene GAPDH was evaluated by real time RT‐PCR. Capture of cell populations enriched for specific regions of the PVN was verified by high relative expression of mRNA for vasopressin in the magnocellular (1±0.55) compared to the medial (0.05±0.01) and pre‐autonomic regions (0.13±0.1), and high relative expression of glucocorticoid receptor mRNA in the medial (1±0.33) versus the magnocellular (0.16±0.03) and pre‐autonomic regions (0.09±0.02). Expression of the three alpha 1 receptor subtypes was not changed by AIH in pre‐autonomic and magnocellular regions of the PVN. In the medial parvocellular region, AIH decreased expression of alpha 1d receptors (N= 1±0.35; AIH = 0.28±0.06), while expression of alpha 1a and alpha 1b receptor subtypes remained unchanged. Using Fos‐IR as an index of neuronal activation, immunohistochemistry experiments found that, compared to continuous hypoxia (2 hr, 10% O 2 ), activation of CRH‐IR neurons in the medial parvocellular region of the PVN was significant but modest in rats exposed to AIH (continuous hypoxia = 28±6%; AIH = 7±1%). It is possible that downregulation of adrenergic alpha 1d receptors in the medial parvocellular region during AIH limits excitation of these neurons. Support or Funding Information Funded by Univ. MO Research Board to CMH and NIH HL 98602.