Role of Q-type Ca2+ channels in vasopressin secretion from neurohypophysial terminals of the rat. Academic Article uri icon

Overview

abstract

  • 1. The nerve endings of rat neurohypophyses were acutely dissociated and a combination of pharmacological, biophysical and biochemical techniques was used to determine which classes of Ca2+ channels on these central nervous system (CNS) terminals contribute functionally to arginine vasopressin (AVP) and oxytocin (OT) secretion. 2. Purified neurohypophysial plasma membranes not only had a single high-affinity binding site for the N-channel-specific omega-conopeptide MVIIA, but also a distinct high-affinity site for another omega-conopeptide (MVIIC), which affects both N- and P/Q-channels. 3. Neurohypophysial terminals exhibited, besides L- and N-type currents, another component of the Ca2+ current that was only blocked by low concentrations of MVIIC or by high concentrations of omega-AgaIVA, a P/Q-channel-selective spider toxin. 4. This Ca2+ current component had pharmacological and biophysical properties similar to those described for the fast-inactivating form of the P/Q-channel class, suggesting that in the neurohypophysial terminals this current is mediated by a 'Q'-type channel. 5. Pharmacological additivity studies showed that this Q-component contributed to rises in intraterminal Ca2+ concentration ([Ca2+]i) in only half of the terminals tested. 6. Furthermore, the non-L- and non-N-component of Ca(2+)-dependent AVP release, but not OT release, was effectively abolished by the same blockers of Q-type current. 7. Thus Q-channels are present on a subset of the neurohypophysial terminals where, in combination with N- and L-channels, they control AVP but not OT peptide neurosecretion.

authors

  • Wang, Gang
  • Dayanithi, Govindan
  • Kim, Sinmei
  • Hom, Dennis
  • Nadasdi, Laszlo
  • Kristipati, Ramasharma
  • Ramachandran, J
  • Stuenkel, E L
  • Nordmann, J J
  • Newcomb, Robert
  • Lemos, J R

publication date

  • July 15, 1997

Research

keywords

  • Arginine Vasopressin
  • Calcium Channels
  • Pituitary Gland, Posterior
  • omega-Conotoxins

Identity

PubMed Central ID

  • PMC1159554

Scopus Document Identifier

  • 0030755669

Digital Object Identifier (DOI)

  • 10.1111/j.1469-7793.1997.351bk.x

PubMed ID

  • 9263915

Additional Document Info

volume

  • 502 ( Pt 2)

issue

  • Pt 2