Role of Q-type Ca2+Channels in Vasopressin Secretion From Neurohypophysial Terminals of the Rat
| Autor: | Sinnei Kim, J. Ramachandran, Govindan Dayanithi, Ramasharma Kristipati, Gang Wang, Laszlo Nadasdi, Dennis Hom, Jean J. Nordmann, Edward L. Stuenkel, Robert Newcomb, José R. Lemos |
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| Rok vydání: | 1997 |
| Předmět: |
medicine.medical_specialty
Vasopressin Arginine Physiology Spider Venoms Biology Oxytocin omega-Conotoxins Membrane Potentials Mice Pituitary Gland Posterior omega-Agatoxin IVA Internal medicine medicine Animals Secretion Nerve Endings Cell Membrane Calcium Channel Blockers Spider toxin Rats Arginine Vasopressin Endocrinology Vasopressin secretion Calcium Cattle Calcium Channels Peptides Neurosecretion Free nerve ending Research Article medicine.drug |
| Zdroj: | The Journal of Physiology. 502:351-363 |
| ISSN: | 0022-3751 |
| Popis: | 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 ω-conopeptide MVIIA, but also a distinct high-affinity site for another ω-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 ω-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 Ca2+-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. |
| Databáze: | OpenAIRE |
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