Role of hydrogen sulfide production in inhibitory action of L-cysteine on isolated porcine irides.

Purpose: To investigate the direct pharmacological actions of L-cysteine, a substrate for the production of H(2)S, on isolated porcine irides in the presence of tone induced by muscarinic receptor stimulation. Furthermore, we examined the underlying mechanism of action of L-cysteine in this smooth muscle.

Methods: Isolated porcine iris muscle strips were set up in organ baths containing oxygenated Krebs buffer solution at 37 degrees C.

Effect of hydrogen sulfide on cyclic AMP production in isolated bovine and porcine neural retinae.

Hydrogen sulfide (H(2)S) has been reported to exert pharmacological effects on neural and non-neural tissues from several mammalian species. In the present study, we examined the role of the intracellular messenger, cyclic AMP in retinal response to H(2)S donors, sodium hydrosulfide (NaHS) and sodium sulfide (Na(2)S) in cows and pigs. Isolated bovine and porcine neural retinae were incubated in oxygenated Krebs buffer solution prior to exposure to varying concentrations of NaHS, Na(2)S or the diterpene activator of adenylate cyclase, forskolin.

Regulation of norepinephrine release from isolated bovine irides by histamine.

In the present study, we investigated the effect of histamine on sympathetic neurotransmission from isolated, superfused bovine irides. We also studied the pharmacology of prejunctional histamine receptors that regulate the release of norepinephrine (NE) from this tissue. The effect of exogenous histamine and various histamine receptor agonists was examined on the release of [(3)H]-norepinephrine ([(3)H]NE) triggered by electrical field stimulation using the Superfusion Method.

Pharmacological consequences of oxidative stress in ocular tissues.

The eye is a unique organ because of its constant exposure to radiation, atmospheric oxygen, environmental chemicals and physical abrasion. That oxidative stress mechanisms in ocular tissues have been hypothesized to play a role in diseases such as glaucoma, cataract, uveitis, retrolental fibroplasias, age-related macular degeneration and various forms of retinopathy provides an opportunity for new approaches to their prevention and treatment, In the anterior uvea, both H2O2 and synthetic peroxides exert pharmacological/toxicological actions tissues of the anterior uvea especially on the sympathetic nerves and smooth muscles of the iris-ciliary bodies of several mammalian species. Effects produced by peroxides require the presence of trace amounts of extracellular calcium and the functional integrity of mitochondrial calcium stores.

Arachidonic acid metabolites and peroxide-induced inhibition of [3H]D-aspartate release from bovine isolated retinae.

We have previously shown that hydrogen peroxide (H2O2) can inhibit K+-depolarization-evoked [3H]D-aspartate release from bovine isolated retinae. In the present study, we investigated the role of arachidonic acid metabolites in the inhibitory response elicited by H2O2 in the bovine retinae. Furthermore, we examined the direct effect of H2O2 on the production of prostaglandins and isoprostanes in this tissue.

Effect of peroxides on [3H]D-aspartate release from bovine isolated retinae.

In the present study, we investigated the effect of naturally occurring and synthetic peroxides on K+-depolarization-evoked release of [3H]D-aspartate from bovine isolated retinae. Furthermore, effect of peroxides on endogenous glutamate concentrations were measured by HPLC in bovine neural retinae and vitreous humor of eyes treated with hydrogen peroxide (H2O2) ex vivo. Both naturally occurring H2O2 (1-100 microM) and synthetic (cumene hydroperoxide, cuOOH; 1-100 microM) peroxides caused a concentration-dependent inhibition of K+-evoked [3H]D-aspartate release without affecting basal tritium efflux.

Glucose-deprivation-induced [3H]D-aspartate release from isolated bovine and human retinae.

The glucose deprivation-induced release of [3H]D-aspartate was studied in bovine and human retinas in a superfusion apparatus. [3H]D-aspartate release was significantly increased upon omitting glucose in the superfusion buffer. This effect was dependent on external Ca2+ because L- and N-type Ca2+-channel blockers, such as diltiazem (1 microM), nitrendipine (1 microM), and omega-conotoxin (100 nM), significantly reduced the effect of glucose-deprivation induced release of [3H]D-aspartate.

Safety and mechanism of appetite suppression by a novel hydroxycitric acid extract (HCA-SX).

A growing body of evidence demonstrates the efficacy of Garcinia cambogia-derived natural (-)-hydroxycitric acid (HCA) in weight management by curbing appetite and inhibiting body fat biosynthesis. However, the exact mechanism of action of this novel phytopharmaceutical has yet to be fully understood. In a previous study, we showed that in the rat brain cortex a novel HCA extract (HCA-SX, Super CitriMax) increases the release/availability of radiolabeled 5-hydroxytryptamine or serotonin ([3H]-5-HT), a neurotransmitter implicated in the regulation of eating behavior and appetite control.

Pharmacology of serotonin receptors modulating electrically-induced [3h]-norepinephrine release from isolated mammalian iris-ciliary bodies.

The pharmacology of prejunctional serotonin (5-HT) heteroreceptors that regulate the release of norepinephrine (NE) was studied in isolated bovine and human iris-ciliary bodies. The effect of exogenous 5-HT and various 5-HT receptor agonists was examined on the release of [3H]-norepinephrine ([3H]NE). Both 5-HT and m-chlorophenyl-biguanide (m-CPBG) caused enhancement in the field-stimulated release of [3H]NE from bovine tissues whereas 5-carboxamidotryptamine (5-CT) had no such effect.