Nav1.9 expression in magnocellular neurosecretory cells of supraoptic nucleus

Exp Neurol. 2014 Mar:253:174-9. doi: 10.1016/j.expneurol.2014.01.004. Epub 2014 Jan 11.

Abstract

Osmoregulation in mammals is tightly controlled by the release of vasopressin and oxytocin from magnocellular neurosecretory cells (MSC) of the supraoptic nucleus (SON). The release of vasopressin and oxytocin in the neurohypophysis by axons of MSC is regulated by bursting activity of these neurons, which is influenced by multiple sources, including intrinsic membrane properties, paracrine contributions of glial cells, and extrinsic synaptic inputs. Previous work has shown that bursting activity of MSC is tetrodotoxin (TTX)-sensitive, and that TTX-S sodium channels Nav1.2, Nav1.6 and Nav1.7 are expressed by MSC and upregulated in response to osmotic challenge in rats. The TTX-resistant sodium channels, NaV1.8 and Nav1.9, are preferentially expressed, at relatively high levels, in peripheral neurons, where their properties are linked to repetitive firing and subthreshold electrogenesis, respectively, and are often referred to as "peripheral" sodium channels. Both sodium channels have been implicated in pain pathways, and are under study as potential therapeutic targets for pain medications which might be expected to have minimal CNS side effects. We show here, however, that Nav1.9 is expressed by vasopressin- and oxytocin-producing MSC of the rat supraoptic nucleus (SON). We also show that cultured MSC exhibit sodium currents that have characteristics of Nav1.9 channels. In contrast, Nav1.8 is not detectable in the SON. These results suggest that Nav1.9 may contribute to the firing pattern of MSC of the SON, and that careful assessment of hypothalamic function be performed as NaV1.9 blocking agents are studied as potential pain therapies.

Keywords: Magnocellular neurosecretory cells; Oxytocin; Sodium channel; Supraoptic nucleus; Vasopressin.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cells, Cultured
  • Electric Stimulation
  • Gene Expression / physiology*
  • Ion Channel Gating / drug effects
  • Male
  • Membrane Potentials / drug effects
  • Membrane Potentials / genetics
  • NAV1.9 Voltage-Gated Sodium Channel / genetics
  • NAV1.9 Voltage-Gated Sodium Channel / metabolism*
  • Neurons / drug effects
  • Neurons / metabolism*
  • Oxytocin / metabolism
  • Patch-Clamp Techniques
  • Rats
  • Sodium Channel Blockers / pharmacology
  • Supraoptic Nucleus / cytology*
  • Tetrodotoxin / pharmacology
  • Vasopressins / metabolism

Substances

  • NAV1.9 Voltage-Gated Sodium Channel
  • Scn11a protein, rat
  • Sodium Channel Blockers
  • Vasopressins
  • Tetrodotoxin
  • Oxytocin