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Multiple calcium channels control neurotransmitter release from rat postganglionic sympathetic nerve terminals.
Author(s) -
Smith A B,
Cunnane T C
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1997.sp021931
Subject(s) - neurotransmitter , excitatory postsynaptic potential , chemistry , voltage dependent calcium channel , calcium channel , p type calcium channel , calcium , neuroscience , t type calcium channel , neurotransmission , electrophysiology , channel blocker , calcium channel blocker , psychology , receptor , biochemistry , organic chemistry
1. Intracellular recording techniques were used to study neurotransmitter release mechanisms in postganglionic sympathetic nerve terminals of the rat isolated anococcygeus muscle. 2. Low concentrations of the N‐type calcium channel blocker omega‐conotoxin GVIA (omega‐CgTX GVIA) irreversibly abolished excitatory junction potentials (EJPs) evoked by trains of < or = five stimuli at 10 Hz. When the frequency of stimulation was increased (10‐50 Hz) trains of stimuli evoked EJPs even in the presence of 1 microM omega‐CgTX GVIA. We have termed this omega‐CgTX GVIA‐resistant release ‘residual release’. EJP amplitude in the presence of omega‐CgTX GVIA depended on both the frequency and number of stimuli in a train. 3. Residual release was inhibited by the P‐type calcium channel blocker omega‐agatoxin IVA (100 nM). However, even in the presence of both toxins, longer trains of stimuli could still evoke neurotransmitter release. 4. Residual release was abolished by omega‐conotoxin MVIIC and by the non‐specific calcium channel antagonist omega‐grammotoxin SIA. Therefore, it would appear that a heterogeneous population of calcium channels is involved in mediating neurotransmitter release from these sympathetic nerve terminals.