Postnatal developmental changes in Ca2+ homeostasis in supraoptic magnocellular neurons

Cell Calcium. 2007 May;41(5):441-50. doi: 10.1016/j.ceca.2006.08.003. Epub 2006 Sep 27.

Abstract

Supraoptic magnocellular neurons (SMNs) undergo dramatic changes in morphological and electrical properties during postnatal development. We investigated the developmental change in Ca2+ homeostasis in SMNs. The decay rate of Ca2+ transients markedly increased during the third postnatal week (PW3) to an adult level. This increase in the Ca2+ decay rate was paralleled by hypertrophy of the SMN somata. Activity of Na+/Ca2+ exchanger (Na/CaX) and sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) was quantified as a decrement in the Ca2+ decay rate caused by extracellular [Na+] reduction and that by thapsigargin, respectively. SERCA activity was negligible during PW2, and markedly increased during PW3. SERCA activity and soma size remained stable thereafter. Na/CaX activity was a major Ca2+-clearance mechanism (CCM) during PW2, increased further during PW3, but was negligible in mature SMNs (PW10). In parallel with the decrease in Na/CaX activity, endogenous Ca2+ buffering capacity declined, resulting that the apparent Ca2+ decay rate remained relatively constant between PW4 and PW10. Replacement of intracellular K+ with Li+ had no effect on Na/CaX activity, suggesting that NCX rather than NCKX comprises Na/CaX. These findings indicate a developmental shift in the balance of CCMs from Ca2+ extrusion via NCX toward Ca2+ sequestration into endoplasmic reticulum via SERCA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Caffeine / pharmacology
  • Calcium / metabolism*
  • Calcium Signaling / drug effects
  • Homeostasis* / drug effects
  • In Vitro Techniques
  • Male
  • Neurons / cytology
  • Neurons / drug effects
  • Neurons / enzymology
  • Neurons / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism
  • Sodium / pharmacology
  • Sodium-Calcium Exchanger / metabolism
  • Supraoptic Nucleus / cytology*
  • Supraoptic Nucleus / growth & development*
  • Thapsigargin / pharmacology

Substances

  • Sodium-Calcium Exchanger
  • Caffeine
  • Thapsigargin
  • Sodium
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium