Metabotropic receptor-activated calcium increases and store-operated calcium influx in mouse Müller cells.

Purpose: Metabotropic receptor agonists that signal through G(q)-coupled pathways increase Ca(2+) in mammalian Müller cells by release from intracellular stores and Ca(2+) influx pathways that have not been well described. The authors examined the involvement of voltage-dependent and non-voltage-dependent Ca(2+) channels in metabotropic muscarinic receptor-activated Ca(2+) increases and store-operated Ca(2+) influx in cultured mouse Müller cells.

Methods: Intracellular Ca(2+) was measured using fluorescence imaging with the ratiometric dye fura-2.

Hyposmotic activation of ICl,swell in rabbit nonpigmented ciliary epithelial cells involves increased ClC-3 trafficking to the plasma membrane.

In mammalian nonpigmented ciliary epithelial (NPE) cells, hyposmotic stimulation leading to cell swelling activates an outwardly rectifying Cl(-) conductance (I(Cl,swell)), which, in turn, results in regulatory volume decrease. The aim of this study was to determine whether increased trafficking of intracellular ClC-3 Cl channels to the plasma membrane could contribute to the I(Cl,swell) following hyposmotic stimulation. Our results demonstrate that hyposmotic stimulation reversibly activates an outwardly rectifying Cl(-) current that is inhibited by phorbol-12-dibutyrate and niflumic acid.

High-voltage-activated calcium channels in Muller cells acutely isolated from tiger salamander retina.

Muller cells mediate retinal function by stabilizing the ionic environment and signal glial network activity via calcium waves. Using whole-cell patch clamp recording, we describe a high-voltage-activated, slowly inactivating Ca channel current in isolated salamander Muller cells that has unusual pharmacological properties. The Ca channel current has an activation midpoint of approximately -8 mV and an inactivation midpoint of approximately -26 mV in 10 mM Ba2+.

An investigation of the neuroprotective effects of tetracycline derivatives in experimental models of retinal cell death.

The purpose of this study was to determine the efficacy and putative mechanisms of action of tetracycline and minocycline in inhibiting retinal cell apoptosis after glutamate-induced excitotoxicity and trophic factor deprivation in a retinal cell line (E1A-NR.3) and in primary mixed retinal cell cultures. In addition, a differentiated PC-12 cell line was used to determine whether minocycline was neuroprotective after trophic withdrawal in a pure neuronal cell line devoid of glia.

Model of endothelin-1-induced chronic optic neuropathy in rat.

Purpose: To describe a model of chronic endothelin (ET)-1 administration to the optic nerve and evaluate its effect on retinal ganglion cell (RGC) and axon survival in rat.

Methods: Osmotic minipumps were surgically implanted in one eye of 113 Brown Norway rats to deliver 0.05, 0.

A3 adenosine and CB1 receptors activate a PKC-sensitive Cl- current in human nonpigmented ciliary epithelial cells via a G beta gamma-coupled MAPK signaling pathway.

(1) We examined A3 adenosine and CB1 cannabinoid receptor-coupled signaling pathways regulating Cl(-) current in a human nonpigmented ciliary epithelial (NPCE) cell line. (2) Whole-cell patch-clamp recordings demonstrated that the A3 receptor agonist, IB-MECA, activates an outwardly rectifying Cl(-)current (I(Cl,Aden)) in NPCE cells, which was inhibited by the adenosine receptor antagonist, CGS-15943 or by the protein kinase C (PKC) activator, phorbol 12,13 dibutyrate (PDBu). (3) Treatment of NPCE cells with pertussis-toxin (PTX), or transfection with the COOH-terminus of beta-adrenergic receptor kinase (ct-betaARK), inhibited I(Cl,Aden).

Regulation of alpha1G T-type calcium channel gene (CACNA1G) expression during neuronal differentiation.

Down-regulation of T-type Ca channel current and mRNA occurs following differentiation of Y79 retinoblastoma cells. To understand how the decrease in expression is linked to cell differentiation, we examined transcriptional regulation of the Cav3.1 Ca channel gene, CACNA1G.

Comparison of the neuroprotective effects of adrenoceptor drugs in retinal cell culture and intact retina.

Purpose: The efficacy of beta1-adrenoceptor (AR)-selective (betaxolol and metoprolol) and nonselective (timolol) antagonists and the alpha2-AR agonist UK14,304 as retinal neuroprotectants was compared and contrasted in an in vitro glutamate excitotoxicity model. The ability of UK14,304, brimonidine, and betaxolol to alter glutamate-receptor-induced changes in intracellular calcium ([Ca2+]i) was also determined in isolated retinal neurons and retinal ganglion cells (RGCs) in an intact retina preparation.

Methods: Neuronal survival was measured in mixed retinal cell cultures treated for 24 hours with media containing 100 microM glutamate, with or without the addition of each of the drugs (1-1000 microM).

The Ca(2+) channel antagonists mibefradil and pimozide inhibit cell growth via different cytotoxic mechanisms.

We show that mitogenic cells expressing T-type Ca(2+) channels (T-channels) are more sensitive to the antiproliferative effects of the drugs pimozide and mibefradil than cells without significant T-channel expression. The growth of Y79 and WERI-Rb1 retinoblastoma cells, as well as MCF7 breast cancer epithelial cells, all of which express T-channel current and mRNA for T-channel subunits, is inhibited by pimozide and mibefradil with IC(50) values between 0.6 and 1.