Cellular electrophysiological effects of chronic fluoxetine and duloxetine administration on serotonergic responses in the aging hippocampus

Brain estrogen alters the effects of the antidepressant sertraline in middle-aged female and male mice

Estrogens are important in regulating mood, especially for females. However, whether tissue-specific estrogen, such as brain estrogen, contributes to the effects of antidepressant treatment has not been determined. The present study used middle-aged aromatase gene knockout (Ar^-/-) mice or overexpression (Thy1-Ar; hGFAP-Ar) mice as brain estrogen models to investigate whether brain estrogen synthesis alters the anti-depressive behaviors of sertraline treatment. Our results showed that depletion of brain estrogen increased depressive-like behavior in females, and elevated brain estrogen reduced depression-like behavior, regardless of sex. These genotype-related behaviors correlated with alterations of monoamine metabolism in the hippocampus (HPC) and the prefrontal cortex (PFC). We also demonstrated that male and female Ar^-/- mice exhibited an attenuation of sertraline-induced anti-depressive behaviors compared to wild-type (WT) mice. The present data suggest that brain estrogen alters depressive-like behaviors and changes the effectiveness of antidepressants in middle-aged mice, regardless of sex.

Duloxetine in the treatment of stress urinary incontinence

This manuscript reviews the pharmacodynamics and pharmacokinetics of duloxetine and its efficacy and safety in women with stress urinary incontinence. Duloxetine is a selective inhibitor of neuronal serotonin and norepinephrine uptake which increases urethral striated muscle activity and bladder capacity. Duloxetine is readily absorbed and extensively metabolized; cytochrome P450 1A2 (CYP1A2) inhibiting drugs can markedly increase duloxetine exposure. The clinical efficacy of duloxetine has consistently been demonstrated in several randomized, double-blind studies in women with moderate-to-severe stress urinary incontinence, but the additional benefit relative to placebo was moderate. Duloxetine treatment is frequently associated with adverse events such as nausea, dry mouth, fatigue, insomnia and constipation, but serious adverse events are rare. Therefore, duloxetine appears suitable for the treatment of stress urinary incontinence.

Duloxetine pharmacology: profile of a dual monoamine modulator

Dysregulation within central monoaminergic systems is believed to underlie the pathology of depression. Drugs that selectively inhibit the reuptake of central monoamines have been used clinically to alleviate symptoms of depressive illnesses. Duloxetine, a novel compound currently under investigation for the treatment of depression, binds selectively with high affinity to both norepinephrine (NE) and serotonin (5-HT) transporters and lacks affinity for monoamine receptors within the central nervous system. It has been suggested that dual inhibition of monoamine reuptake processes may offer advantages over other antidepressants currently in use. In preclinical studies, duloxetine mimics many physiologic effects of antidepressants. Consistent with other antidepressants, duloxetine, by acute administration, elevates extracellular monoamine levels, while by chronic administration it does not alter basal monoamine levels. Like the selective serotonin reuptake inhibitor, fluoxetine, by microiontophoretic application, duloxetine inhibits neuronal cell firing. However, in comparison with fluoxetine, duloxetine is a more potent serotonin reuptake inhibitor. Furthermore, in behavioral experiments, duloxetine attenuates immobility in forced swim tests in animal models of depression to a greater extent than several other commonly used antidepressants. In a six-week open label uncontrolled study, duloxetine was evaluated in patients with a history of depression. Duloxetine was effective in treating depression as determined by marked reduction in Hamilton Depression Rating scores. Adverse effects reported during duloxetine treatment were minor and similar to those of other antidepressants. In an eight-week multicenter, double-blind, placebo-controlled study in patients with a major depressive disorder, duloxetine was effective as an antidepressant, particularly in patients with greater symptom severity. Only limited data are available regarding the pharmacokinetic profile of duloxetine in humans, although a half-life of 10 to 15 h has been reported. Studies conducted in healthy human subjects confirm the preclinical profile of duloxetine as an inhibitor of 5-HT and NE reuptake. Taken together, existing data suggest that duloxetine is a novel and effective antidepressant.

Aging affects transcranial magnetic modulation of hippocampal evoked potentials

Transcranial magnetic stimulation (TMS) is being proposed as a method of choice for the treatment of clinical depression, yet its action in the brain is still not well understood. In previous studies we found that TMS has a long-term effect on reactivity of the hippocampus to perforant path stimulation. Since the efficacy of antidepressants is highly age-dependent, we studied possible age-related effects of TMS on hippocampal evoked responses. Young adult (3 months), aging (10 months) and aged (24-26 months) awake rats were subjected to daily TMS for one week, followed by measurements of several parameters of reactivity to perforant path stimulation in the anesthetized rat. TMS did not affect responses of the hippocampus to single perforant path stimulation, but reduced drastically paired-pulse and frequency dependent depression in the young and aging but not the old rats. Likewise, TMS increased LTP expression in the young but not the old rats, and reduced the efficacy of serotonin modulation of reactivity of the hippocampus, in the young but not the old rats. Thus, long term effects of chronic TMS on local GABAergic inhibition are highly age dependent.

Changes in 5-HT(7) serotonin receptor mRNA expression with aging in rat brain

We examined 5-HT(7) receptor mRNA expression with in situ hybridization histochemistry in the brains of young (3 months), middle-aged (12 months) and old rats (24 months). In the ventral CA3 area of the hippocampus 5-HT(7) mRNA expression is reduced by approximately 30% between young and middle age without further decline between middle and old age. In other brain areas 5-HT(7) mRNA expression is unaffected by age.