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Na + ‐Activated K + Channels in Rat Supraoptic Neurones
Author(s) -
Bansal V.,
Fisher T. E.
Publication year - 2016
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/jne.12394
Subject(s) - vasopressin , oxytocin , medicine , endocrinology , patch clamp , tetrodotoxin , immunocytochemistry , hypothalamus , chemistry , biophysics , channel blocker , western blot , intracellular , biology , electrophysiology , biochemistry , calcium , gene
The magnocellular neurosecretory cells ( MNC s) of the hypothalamus secrete the neurohormones vasopressin and oxytocin. The systemic release of these hormones depends on the rate and pattern of MNC firing and it is therefore important to identify the ion channels that contribute to the electrical behaviour of MNC s. In the present study, we report evidence for the presence of Na + ‐activated K + ( K N a ) channels in rat MNC s. K N a channels mediate outwardly rectifying K + currents activated by the increases in intracellular Na + that occur during electrical activity. Although the molecular identity of native K N a channels is unclear, their biophysical properties are consistent with those of expressed Slick (slo 2.1) and Slack (slo 2.2) proteins. Using immunocytochemistry and Western blot experiments, we found that both Slick and Slack proteins are expressed in rat MNC s. Using whole cell voltage clamp techniques on acutely isolated rat MNC s, we found that inhibiting Na + influx by the addition of the Na + channel blocker tetrodotoxin or the replacement of Na + in the external solution with Li + caused a significant decrease in sustained outward currents. Furthermore, the evoked outward current density was significantly higher in rat MNC s using patch pipettes containing 60 m m Na + than it was when patch pipettes containing 0 m m Na + were used. Our data show that functional K N a channels are expressed in rat MNC s. These channels could contribute to the activity‐dependent afterhyperpolarisations that have been identified in the MNC s and thereby play a role in the regulation of their electrical behaviour.