title: cAMP-dependent inward rectifier current in neurons of the rat suprachiasmatic nucleus.
abstract: Electrophysiological properties of the inward rectification of neurons in the rat suprachiasmatic nucleus (SCN) were examined by using the single-electrode voltage-clamp method, in vitro. Inward rectifier current (IH) was produced by hyperpolarizing step command potentials to membrane potentials negative to approximately -60 mV in nominally zero-Ca2+ Krebs solution containing tetrodotoxin (1 microM), tetraethylammonium (40 mM), Cd2+ (500 microM) and 4-aminopyridine (1 mM). IH developed during the hyperpolarizing step command potential with a duration of up to 5 s showing no inactivation with time. IH was selectively blocked by extracellular Cs+ (1 mM). The activation of the H-channel conductance (GH) ranged between -55 and -120 mV. The GH was 80-150 pS (n = 4) at the half-activation voltage of -84 +/- 7 mV (n = 4). The reversal potential of IH obtained by instantaneous current voltage (I/V) relations was -41 +/- 6 mV (n = 4); it shifted to -51 +/- 8 mV (n = 3) in low-Na+ (20 mM) solution and to -24 +/- 4 mV (n = 4) in high-K+ (20 mM) solution. Forskolin (1-10 microM) produced an inward current and increased the amplitude of IH. Forskolin did not change the half-activation voltage of GH. 8-Bromo-adenosine 3',5'-cyclic monophosphate (8-Br-cAMP, 0.1-1 mM) and dibutyryl-cAMP (0.1-1 mM) enhanced IH. 3-Isobutyl-1-methylxanthine (IBMX, 1 mM) also enhanced IH. The results suggest that the inward rectifier cation current is regulated by the basal activity of adenylate cyclase in neurons of the rat SCN.
authors.affiliation: Department of Physiology, Kurume University School of Medicine, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Akasu
authors.forename: S
authors.initials: S
authors.lastname: Shoji
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D011921:Rats, Inbred WKY; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
chemical_list: D007473:Ion Channels; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine