Neurosteroids modulate calcium currents in hippocampal CA1 neurons via a pertussis toxin-sensitive G-protein-coupled mechanism

摘要: The inhibition of Ca2+ channel currents by endogenous brain steroids was examined in freshly dissociated pyramidal neurons from the adult guinea pig hippocampal CA1 region. steady-state peak current evoked depolarizing steps -80 to -10 mV occurred a concentration-dependent manner with following IC50 values: pregnenolone sulfate (PES), 11 nM; (PE), 130 and allotetrahydrocorticosterone (THCC), 298 nM. THCC, PE, PES depressed fraction maximal 60% total current. However, substitution an acetate group for on resulted complete loss activity. Progesterone had no effect (4% at 100 microM). Intracellular dialysis current; concomitant extracellular perfusion showed normal inhibitory activity, suggesting that steroid binding site can only be accessed extracellularly. Analysis tail demonstrated THCC slowed rate activation deactivation change voltage dependence activation. Inhibition dependent. primarily inhibits omega-conotoxin (CgTX)-sensitive or N-type PE nonselective inhibiting both CgTX- nifedipine (NIF)-sensitive These neurosteroids CgTX/NIF-insensitive In isolated pertussis toxin (PTX)-treated animals chronic intracerebroventricular infusion (1000 ng/24 hr 48 hr), PES, significantly diminished. GDP-beta-S (500 microM) also diminished neurosteroid general kinase inhibitors H-7 (100 microM), staurosporine (400 nM), 20 amino acid protein inhibitor (1 prevented more specific C (PKC), pseudosubstrate (PKCI 19–36) (1–2 bisindolylmaleimide Rp- cAMP cAMP-dependent (PKA), current.(ABSTRACT TRUNCATED AT 400 WORDS)