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Modulation of N‐type Ca 2+ currents by agmatine via imidazoline I 2 receptor activation in rat coeliac ganglion neurons (1172.4)
Author(s) -
Chung Seungsoo
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.1172.4
Subject(s) - agmatine , imidazoline receptor , chemistry , pertussis toxin , endocrinology , biophysics , medicine , receptor , pharmacology , biochemistry , g protein , biology , enzyme , putrescine
Agmatine, an imidazoline deriviatives, suppress the vasopressor sympathetic outflow to produce hypotension. This effect has been known to be mediated in part by suppressing sympathetic outflow via acting imidazoline I 2 receptors (IR 2 ) at postganglionic sympathetic neurons. But, the cellular mechanism of IR 1 ‐induced inhibition of noradrenaline (NA) release is still unknown. We therefore, investigated the effect of IR1 activation on voltage‐dependent Ca 2+ channels which is known to play an pivotal role in regulating NA in rat coeliac ganglion neurons, using the conventional whole‐cell patch‐clamp method. In the presence of rauwolscine (3 uM), which blocks a2‐adrenoceptor (Ra 2 ), agmatine inhibited voltage‐dependent Ca2+ current (I Ca ) by about 30%. This agmatine‐induced inhibition was almost completely prevented by efaroxan (10 uM) which blocks IR1 as well as Ra 2 . In addition, w‐conotoxin (CgTx) GVIA (1 uM) occluded agmatine‐induced inhibition of I Ca , but, agmatine‐induced I Ca inhibition was not affected by pertussis toxin (PTX) nor shows any characteristics of voltage‐dependent inhibition These data suggest that agmatine inhibit voltage‐dependent N‐type Ca 2+ current (I Ca–N ) via activating IR1. Finally, agmatine significantly decreased the frequency of AP firing in a partially reversible manner. This inhibition of AP firing was almost completely occluded in the presence of w‐CgTx. Taken together, our results suggest that activation of IR 2 in coeliac ganglion neurons reduced I Ca–N in a PTX‐and voltage‐insensitive pathway, and this inhibition attenuated repetitive AP firing in coeliac ganglion neurons.