Enhancement of hippocampal pyramidal cell excitability by the novel selective slow-afterhyperpolarization channel blocker 3-(triphenylmethylaminomethyl)pyridine (UCL2077).

The slow afterhyperpolarization (sAHP) in hippocampal neurons has been implicated in learning and memory. However, its precise role in cell excitability and central nervous system function has not been explicitly tested for 2 reasons: 1) there are, at present, no selective inhibitors that effectively reduce the underlying current in vivo or in intact in vitro tissue preparations, and 2) although it is known that a small conductance K(+) channel that activates after a rise in [Ca(2+)](i) underlies the sAHP, the exact molecular identity remains unknown. We show that 3-(triphenylmethylaminomethyl)pyridine (UCL2077), a novel compound, suppressed the sAHP present in hippocampal neurons in culture (IC(50) = 0.

The SK3 subunit of small conductance Ca2+-activated K+ channels interacts with both SK1 and SK2 subunits in a heterologous expression system.

The aim of this study was to determine whether functional heteromeric channels can be formed by co-assembly of rat SK3 (rSK3) potassium channel subunits with either SK1 or SK2 subunits. First, to determine whether rSK3 could co-assemble with rSK2 we created rSK3VK (an SK3 mutant insensitive to block by UCL 1848). When rSK3VK was co-expressed with rSK2 the resulting currents had an intermediate sensitivity to UCL 1848 (IC50 of approximately 5 nM compared with 120 pM for rSK2 and >300 nM for rSK3VK), suggesting that rSK3 and rSK2 can form functional heteromeric channels.

Small conductance Ca2+-activated K+ channels formed by the expression of rat SK1 and SK2 genes in HEK 293 cells.

The rat SK1 gene (rSK1) does not form functional Ca2+-activated potassium channels when expressed alone in mammalian cell lines. Using a selective antibody to the rSK1 subunit and a yellow fluorescent protein (YFP) tag we have discovered that rSK1 expression produces protein that remains largely at intracellular locations. We tested the idea that rSK1 may need an expression partner, rSK2, in order to form functional channels.

Tritylamino aromatic heterocycles and related carbinols as blockers of ca 2+-activated potassium ion channels underlying neuronal hyperpolarization.

A series of novel aromatic tritylamino heterocycles has been synthesized and the compounds have been tested in comparison with clotrimazole for their ability to inhibit the slow afterhyperpolarization current (sI (AHP)) in cultured rat hippocampal pyramidal neurones. Some analogues of the clotrimazole metabolite, 2-chlorophenyl-diphenyl methanol, having different chlorination substitution in the triphenyl group have also been examined. Two compounds in particular, 3-[(2-chlorophenyl)-diphenylmethylamino] pyridine (3a, UCL 1880) and 2-tritylaminothiazole (6, UCL 2027), are of special interest; they are effective blockers of the sI (AHP) (IC (50) = 1.

K+ currents generated by NMDA receptor activation in rat hippocampal pyramidal neurons.

Long lasting outward currents mediated by Ca2+-activated K+ channels can be induced by Ca2+ influx through N-methyl-D-aspartate (NMDA)-receptor channels in voltage-clamped hippocampal pyramidal neurons. Using specific inhibitors, we have attempted to identify the channels that underlie these outward currents. At a holding potential of -50 mV, applications of 1 mM NMDA to the soma of cultured hippocampal pyramidal neurons induced the expected inward currents.