Seasonal affective disorders

Seasonal affective disorder is a pattern of major depressive episodes that occur and remit with changes in seasons. It may be seen in major depressive or bipolar disorders, as described in the Diagnostic and Statistical. Manual of Mental Disorders (DSM-IV). The most recognized form of seasonal affective disorder, "winter depression," is characterized by recurrent episodes of depression, hypersomnia, augmented appetite with carbohydrate craving, and weight gain that begin in the autumn and continue through the winter months. Physicians have many options for treating seasonal affective disorder. While questions regarding the validity of seasonal affective disorder as a syndrome and the mechanism of action of light therapy continue to be investigated, the established effectiveness of light therapy in patients with winter depression supports the usefulness of assessment for this seasonal pattern and consideration of light therapy as an option in addition to existing treatment choices.

The antiplatelet aggregatory activity of Acacia nilotica is due to blockade of calcium influx through membrane calcium channels

1. The extract of Acacia nilotica (A. nilotica) blocked platelet aggregation mediated by platelet agonists, arachidonic acid (0.75 mM), ADP (4.3 microM), platelet activating factor (800 nM) and collagen (638 nM) in a dose-dependent manner. 2. The extract (0.21-1.4 mg/ml) blocked the platelet aggregation induced by Ca2+ ionophore, A-23187 (6 microM), in a dose-dependent manner, indicating that the Ca2+ influx is involved in aggregation. 3. The plant extract also inhibited aggregation in platelets pretreated with phorbol, 12-myristate, 13-acetate (196 nM) alone or in combination with ADP (4.3 microM), indicating an effect on protein kinase C. 4. These results indicate that the antiplatelet aggregatory activity of the extract of A. nilotica is mainly due to blockade of Ca2+ channels, although evidence also suggests the involvement of protein kinase C.

Anti-thrombotic and anti-inflammatory activities of protopine

The effects of protopine on human platelet aggregation and arachidonic acid (AA) metabolism via cyclooxygenase (COX) and lipoxygenase (LOP) enzymes were examined. Platelet aggregation induced by various platelet agonists (AA, ADP, collagen and PAF) was strongly inhibited by protopine in a concentration-related manner. The IC50 values (microM) of protopine (mean +/- SEM) against: AA; 12 +/- 2: ADP; 9 +/- 2: collagen; 16 +/- 2 and PAF; 11 +/- 1, were much less than those observed for aspirin. In addition, protopine selectively inhibited the synthesis of thromboxane A2 (TXA2) via COX pathway and had no effect on the LOP pathway in platelets. In vivo, pretreatment with protopine (50-100 mg kg-1) protected rabbits from the lethal effects of AA (2 mg kg-1) or PAF (11 micrograms kg-1) in dose-dependent fashion. Protopine (50-100 mg kg-1) also inhibited carrageenan-induced rat paw oedema with a potency of three-fold as compared to aspirin. These results are suggestive that protopine acts as a potent inhibitor of thromboxane synthesis and PAF with anti-inflammatory properties.

Effects of lipoproteins on cyclo-oxygenase and lipoxygenase pathways in human platelets

The products of arachidonic acid (AA) metabolism in platelets play an important role in platelet shape change, adhesion and aggregation which may participate in the pathogenesis of ischemic heart disease and thrombosis. Since lipoproteins are also involved in the pathogenesis of thrombo-embolic disorders, the effect of human lipoproteins (HDL, LDL, VLDL) on AA metabolism in human platelets was investigated. Lipoproteins were separated by density gradient zonal ultracentrifugation. The effects of lipoproteins on production of AA metabolites in human platelets i.e., thromboxane A2 (TXA2) and hydroxy-eicosatetraenoic acids (HETEs) were examined using radiometric thin layer chromatography coupled with automated data integrator system. In human platelets, HDL inhibited 12-HETE and TXA2 formation in a concentration-dependent manner. LDL had a strong inhibitory effect on TXA2 production and a weak inhibitory effect on 12-HETE production. VLDL had no effect on platelet AA metabolism. These findings point to a new facet of lipoproteins action and suggest that lipoproteins may have a physiological role in the regulation of AA metabolism in platelets.

Chemistry and biological activity of a tryptamine and beta-carboline series of bases

Twenty-six derivatives of harmaline and tetrahydroharmine were prepared and characterized by UV, IR, MS, and NMR spectroscopy. They were tested for their antimicrobial, antiplatelet aggregation and cytotoxic activity. Their effect on central nervous system was also studied.

Protein kinase C inhibitor, chelerythrine, potentiates the adrenaline-mediated aggregation of human platelets through calcium influx

The role of protein kinase C (PKC) using its selective inhibitor, chelerythrine, in agonist mediated platelet aggregation was studied. Chelerythrine had no effect on the aggregation induced by adrenaline, PAF, collagen and ADP at the maximum doses of these agonists. However, it potentiated the aggregatory response of low doses of adrenaline (0.4-1 microM). Such an effect was blocked by Ca(++)-channel blockers, verapamil and diltiazem indicating the likely involvement of Ca++ influx in the platelet aggregation during the cascade.

An open trial of fluvoxamine therapy for panic disorder complicated by depression

BACKGROUND

The efficacy of fluvoxamine in the treatment of panic disorder complicated by depression was investigated in an 8-week, single-group, open-label, flexible-dose trial.

METHOD

Seventeen patients having a principal diagnosis of panic disorder and scoring 16 or more on the 17-item Hamilton Rating Scale for Depression were treated with fluvoxamine at a mean final dose of 213 mg/ day. Outcome was assessed on measures of panic attacks, general and anticipatory anxiety, agoraphobic avoidance, depression, disability, and fear of anxiety symptoms.

RESULTS

Subjects improved on all measures except agoraphobic avoidance. Thirteen either chose to remain on fluvoxamine treatment after the study ended or resumed taking it after a brief period without medication or on another medication.

CONCLUSION

Fluvoxamine appears to be effective in this population.

Phosphatidylinositol 3-kinase inhibitor, wortmannin, inhibits 5-hydroxytryptamine-mediated potentiation of platelet aggregation induced by epinephrine

The role of phosphatidylinositol 3-kinase (PI 3-kinase) was investigated in human platelets exposed to varying doses of 5-hydroxytryptamine (5-HT) and subthreshold doses of epinephrine. The synergistic effect of 5-HT on epinephrine-induced aggregation was blocked by a specific inhibitor of PI 3-kinase, wortmannin, in a dose-dependent manner. However, there was no effect of inhibitors of protein kinase A (PKA) or protein kinase C (PKC). These studies suggest a role of PI 3-kinase in the 5-HT induced potentiation of epinephrine-mediated platelet aggregation.

Altered platelet activating factor metabolism in insulin dependent diabetes mellitus

Diabetes mellitus is associated with several abnormalities of platelet function. Recent studies have shown that the blood level of platelet activating factor (PAF), a potent inducer of platelet aggregation, is elevated in insulin dependent diabetes mellitus (IDDM) and remains unchanged in non-insulin dependent diabetes mellitus (NIDDM) patients. However, the mechanism of this increase in PAF levels has not been determined. In this study we have measured the activity of plasma PAF acetylhydrolase (an enzyme that regulates PAF levels) and lipoprotein levels in control subjects and diabetic patients. The data presented show that plasma PAF acetylhydrolase activity is significantly decreased in IDDM and is not altered in NIDDM patients. The lipoprotein levels were similar in control and diabetic subjects and there was no correlation between lipoprotein levels and PAF acetylhydrolase activity. These results suggest that the elevated levels of PAF in IDDM patients could be due to a decrease in plasma PAF acetylhydrolase activity.

Antithrombotic activity of clove oil

Clove oil inhibited human platelet aggregation induced by arachidonic acid (AA), platelet-activating factor (PAF) or collagen. Clove oil was a more effective inhibitor for aggregation induced by AA and PAF (IC50:4 and 6 microM respectively) than collagen (IC50: 132 microM). The in vivo experiments in rabbits showed that clove oil (50-100 mg/kg) afforded 100% protection against PAF (11 mg/kg, i.v.) and 70% protection against AA (2.0 mg/kg, i.v.)-induced thrombosis and shock due to pulmonary platelet thrombosis. It also inhibited thromboxane-A2 and 12-HETE production by human platelets incubated with [C14] AA. These results are indicative that clove oil is inhibitory of platelet aggregation and thromboxane synthesis and may act as anti-thrombotic agent.

Dual inhibition of platelet-activating factor and arachidonic acid metabolism by ajmaline and effect on carrageenan-induced rat paw oedema

The effects of ajmaline on human platelet aggregation, arachidonate metabolism and platelet activating factor (PAF)-induced lethality in rabbits were examined. Platelet aggregation induced by several stimuli (ADP, collagen, and PAF) was inhibited by increasing concentrations of ajmaline. The potency of ajmaline was higher when PAF was employed as stimulating agent in comparison with other agonists (IC50 70, 270 and 380 microM for PAF, ADP and collagen, respectively) whereas ajmaline had no effect against arachidonic acid-induced aggregation. In contrast however, ajmaline inhibited arachidonate metabolism by platelet homogenates. The formation of both thromboxane A2 and 12-hydroxy-eicosatetraenoic acid was inhibited by ajmaline with comparable potencies. Pretreatment of rabbits with ajmaline (50 mg kg-1) completely abolished the lethal effects of PAF (11 micrograms kg-1) given intravenously (P < 0.001). In addition, ajmaline at doses ranging from 50 to 100 mg kg-1 inhibited carrageenan-induced rat paw oedema (P < 0.001). In this test ajmaline was three times more potent than aspirin. In the light of these results we conclude that ajmaline, a known anti-arrhythmic agent is a PAF antagonist and a dual inhibitor of platelet cyclo-oxygenase and lipoxygenase enzymes with anti-inflammatory properties.