. . . . . . . . . . . . . . . "kin(p(SFAM:\"PRKA Family\")) -> path(SDIS:\"I(f) F-channel current\")" . "Approximately 61,000 statements." . "Copyright (c) 2011-2012, Selventa. All rights reserved." . "BEL Framework Large Corpus Document" . . "20131211" . "Several factors can influence the activation of f-channels. ?-Adrenergic receptor activation stimulates (21) while muscarinic agonists inhibit If (129). This regulation is mediated by direct activation of f-channels by cAMP (50, 128), which facilitates channel opening (126). DiFrancesco and Tortora (128) failed to observe a direct regulation of SAN f-channels by purified protein kinase A (PKA) (128). In SAN cells, direct regulation of voltage dependence by cAMP can quantitatively account for If regulation by autonomic agonists (126). The existence of a PKA-mediated regulation of If has been suggested by Chang et al. (80) in canine Purkinje cells and in murine stem cells derived from cardiomyocytes (1). Intracellular Ca2+ have been reported to positively regulate If by either increasing current conductance (171) or by positively shifting the current voltage dependence (416). The mechanisms by which Ca2+ regulate If has not been elucidated. Inside-out patch-clamp experiments seem to exclude a direct Ca2+ effect on f-channels (540)." . . "Selventa" . . . . "2014-07-03T14:33:22.699+02:00"^^ . . .