Premium
Calcium channels coupled to neurotransmitter release at neonatal rat neuromuscular junctions
Author(s) -
Siri Marcelo D. Rosato,
Uchitel Osvaldo D.
Publication year - 1999
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 - 10.1111/j.1469-7793.1999.533ae.x
Subject(s) - voltage dependent calcium channel , nifedipine , nitrendipine , calcium channel , neurotransmitter , calcium channel blocker , channel blocker , chemistry , neuromuscular junction , l type calcium channel , calcium , endocrinology , t type calcium channel , medicine , neuroscience , receptor , biology
1 The effects of different calcium channel blockers (ω‐agatoxin IVA (ω‐Aga IVA), ω‐conotoxin GVIA (ω‐CgTx GVIA) and dihydropyridines) were tested on spontaneous and evoked transmitter release at embryonic and newborn rat neuromuscular junctions (NMJs). 2 The nerve‐evoked transmitter release quantal content ( m ) was strongly reduced by the P/Q‐type voltage‐dependent calcium channel (VDCC) blocker ω‐Aga IVA (100 nM) at newly formed endplates of embryos and 0‐ to 11‐day‐old rats, in agreement with the effect of this blocker on transmitter release at mature and reinnervating muscles. 3 ω‐CgTx GVIA (1–5 μ m ), the N‐type VDCC blocker, also caused a significant reduction in m at newly formed NMJs early in development (embryos and 0‐ to 4‐day‐old rats), while it was ineffective in more mature animals (5‐ to 11‐day‐old rats). 4 L‐type channel blockers, nitrendipine (1 μ m ) and nifedipine (1 μ m ), did not significantly affect neurally evoked release at developing NMJs. However, nifedipine (10 μ m ) was able to increase m significantly at 0‐ to 4‐day‐old rat NMJs. 5 At developing NMJs, K + ‐evoked transmitter release was dependent on Ca 2+ entry through VDCCs of the P/Q‐type family (100 n m ω‐Aga IVA reduced 70% of the K + ‐evoked miniature endplate potential frequency). N‐ and L‐type VDCC blockers did not affect this type of release. 6 We conclude that at rat neuromuscular junctions the presynaptic calcium channel types involved in transmitter release undergo developmental changes during the early postnatal period.