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OVLT Neurons Exhibit Exquisite Osmosensitivity to Elevated NaCl Concentrations
Author(s) -
Kinsman Brian,
Browning Kirsteen,
Stocker Sean
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.988.1
Subject(s) - osmoreceptor , osmotic concentration , osmole , electrophysiology , medicine , repolarization , endocrinology , chemistry , biophysics , biology , tonicity
The brain responds to changes in osmolarity through specialized osmosensitive neurons of the organum vasculosum of the lamina terminalis (OVLT). However, prior studies assessed OVLT neuronal responses to supraphysiologic changes in osmolarity (~5 ‐ 15%). Therefore, this study aimed to establish that OVLT neurons are sensitive to physiologic 5 ‐ 10mOsm elevations (~1.5 ‐ 3.5%) in bath NaCl using whole‐cell recordings of adult OVLT neurons in slices. We measured changes in action potential (AP) discharge frequency to 5 mOsm increases in NaCl. 56% of OVLT neurons (9/16) were osmosensitive as defined by a 25% increase in discharge frequency. Osmosensitive neurons' (n = 9) peak AP discharge increased significantly from a 295 mOsm baseline (0.88±0.25 Hz) by 154% to 300 mOsm (1.66±0.33 Hz; p < 0.05) and by 252% to 305 mOsm (1.97±0.34 Hz; p < 0.05) stimuli. Conversely, non‐osmosensitive neurons' (n = 7) peak AP discharge did not significantly change from a 295 mOsm baseline (0.51±0.16 Hz) to 300 mOsm (0.73±0.24 Hz) and 305 mOsm (0.57±0.22 Hz) stimuli (p > 0.05). Linear regression analysis showed that osmosensitive neurons exhibited concentration‐dependent increases in discharge frequency to hyperosmotic challenges (r 2 = 0.284), but non‐osmosensitive neurons did not (r 2 = 0.00374). Still, osmosensitive and non‐osmosensitive neurons did not differ with regard to input resistance, AP threshold, AP duration, afterhyperpolarization magnitude or repolarization rate. These data demonstrate, for the first time, that OVLT neurons exhibit exquisite sensitivity to 1‐3% increases in osmolarity, and may initiate homeostasis to physiologic elevations in circulating sodium.