Effects of fluoxetine hydrochloride and fluvoxamine maleate on different preparations of isolated guinea pig and rat organ tissues

The Effect of Sertraline on Hemodynamic Parameters and Nitric Oxide Production in Isolated Rat Hearts Subjected to Ischemia and Reperfusion

Purpose

The aim of the study was to investigate the effect of sertraline on the rat heart during ischemia and reperfusion and to determine its effect on NO production.

Materials and methods

The study was performed on isolated rat hearts. Hearts from three groups were perfused with sertraline at three different concentrations and subjected to global ischemia and reperfusion. Hearts from the other three groups were perfused with the same concentrations of sertraline but without the ischemia/reperfusion process. Two control groups were perfused with the Krebs-Henseleit solution only with and without ischemia/reperfusion process. Coronary flow (CF), heart rate (HR), left ventricular developed pressure (LVDP) and maximum rate of rise of left ventricular pressure (dP/dt max) were measured. Perfusate effluent was collected to determine creatine phosphokinase (CPK) and nitrate plus nitrite (NOx) levels.

Results

In non-ischemic groups, sertraline at the concentration of 10 μmol/L exerts a strong vasodilatory effect on CF, and after a short positive inotropic effect, it exerts a strong inotropic and chronotropic negative effect on isolated rat hearts and causes a direct damage to cardiomyocytes. At the concentration of 1 μmol/L, sertraline exerts an increasing negative inotropic effect. There were no hemodynamic differences between any of groups of hearts subjected to reperfusion. Sertraline had no effect on the nitric oxide concentration in coronary effluent neither in rat hearts subjected to ischemia/reperfusion nor in non-ischemic conditions.

Conclusion

Sertraline at dose 10 μmol/L exerts a strong vasodilatory effect on coronary flow, and after a short positive inotropic effect, it exerts a strong negative effect on isolated rat hearts, causing a direct damage to cardiomyocytes. Sertraline had no effect on the nitric oxide concentration in coronary effluent.

Fluoxetine Treatment Induces Seizure Behavior and Premature Death in APPswe/PS1dE9 Mice

Treatment of Alzheimer's disease (AD) patients with the antidepressant fluoxetine is known to improve memory and cognitive function. However, the mechanisms underlying these effects are largely unknown. To unravel these mechanisms, we aimed to treat APPswe/PS1dE9 mice with fluoxetine. Unexpectedly, with time, an increased number of animals displayed seizure behavior and died. Although spontaneous behavioral seizures have been reported previously in this mouse model, the observation of seizures and death consequential to fluoxetine treatment is new. Our results warrant further research on the underlying mechanisms as this may refine the treatment of AD patients.

Quantitative assessment of photostability and photostabilisation of Fluvoxamine and its design for actinometry

Wavelength-dependent forwardand reverseFluvo quantum yields have been reported.

The effect of fluvoxamine on ouabain-induced arrhythmia in isolated guinea-pig atria

The effect of fluvoxamine (FLV) a selective serotonin reuptake inhibitor agent was studied on ouabain-induced arrhythmia in spontaneously beating isolated guinea-pig atria. FLV (8-64 microM) caused a dose-dependent decrease in the rate of contractions (7-52%) and in the contractile force (11-57%). Ouabain alone (2 microM) produced arrhythmia at 4.6 min and asystole at 17.4 min. Pre-administration of the atria with FLV (32 microM) significantly increased the time required to produce arrhythmia by ouabain to 14.6 min, prolonged the beating of atria to more than 58.6 min and delayed the occurrence of asystolia. The pattern of contractile force induced by FLV+ouabain was more regular than that produced by ouabain alone. These findings indicate that FLV produces direct cardiac action, probably due to the inhibition of cardiac Na+ and Ca2+ channels. Our results suggest that FLV may reduce the membrane conduction through inhibition of ionic channels which decrease ouabain-induced arrhythmia.

Serotonin reuptake inhibitors fluoxetine and citalopram relax intestinal smooth muscle

Selective serotonin reuptake inhibitor antidepressants (SSRIs) exert depressant effects on cardiac myocytes and vascular smooth muscle cells by inhibiting Ca2+ channels. We hypothesized that the SSRIs fluoxetine and citalopram affect the contractile activity of intestinal smooth muscle by interfering with Ca2+ entry and (or) signaling pathways. The effects of fluoxetine and citalopram on contractions of guinea-pig ileum longitudinal muscle-myenteric plexus preparations (LMMP) were compared with the effects of the voltage-operated Ca2+ channel inhibitors nifedipine and diltiazem. In a concentration-dependent manner, nifedipine, diltiazem, fluoxetine, and citalopram elicited relaxation of LMMPs contracted by electrical field stimulation (EC50 values of 4 × 10–7 M, 1.4 × 10–6 M, 1.4 × 10–5, and 6.8 × 10–6 M, respectively). Nifedipine, diltiazem, fluoxetine, and citalopram also relaxed LMMPs contracted with a depolarizing concentration of KCl (48 mM; EC50 values of 1.8 × 10–8 M, 1.4 × 10–7 M, 3.7 × 10–6 M, and 6.3 × 10–6, respectively), a response that could be reversed by increasing the extracellular Ca2+ concentration (2.5–30 mM). These data suggest that fluoxetine and citalopram elicit relaxation of intestinal smooth muscle, likely by inhibiting Ca2+ channel(s). This effect may be of clinical importance.Key words: fluoxetine (Prozac(r)), citalopram (Seropram(r)), nifedipine, diltiazem, L-type Ca2+ channels, intestinal smooth muscle.

COMPARISON OF PERIPHERAL INHIBITORY EFFECTS OF CLOMIPRAMINE WITH SELECTIVE SEROTONIN RE-UPTAKE INHIBITORS ON CONTRACTION OF VAS DEFERENS:

PURPOSE

We compared the peripheral inhibitory effects of the tricyclic antidepressant clomipramine with those of various selective serotonin re-uptake inhibitors on the contractile response of the vas deferens.

MATERIALS AND METHODS

The contractile responses of 17 circular smooth muscle strips of human vas deferens to 10-4 M. norepinephrine were observed in the absence and presence of clomipramine, and the selective serotonin re-uptake inhibitors fluoxetine, sertraline and paroxetine. The intraluminal pressure response of rat vas deferens to electrical stimulation of the hypogastric nerve was measured in 5 rats in the central plus peripheral effect group before and after the intravenous injection of 4.2 mg./kg. clomipramine or 8.3 mg./kg. sertraline. The pressure response to each agent was also observed after the transection of all proximal sympathetic input to the hypogastric nerve in 5 animals in the peripheral effect group.

RESULTS

Clomipramine was about 100-fold more potent than sertraline, fluoxetine or paroxetine for inhibiting the norepinephrine induced contraction of human vasal muscle strips. The inhibitory effect of sertraline on rat intravasal pressure in the peripheral effect group was significantly lower than in the central plus peripheral effect group (p <0.05), while no significant difference was noted in the 2 groups regarding clomipramine. The effect of clomipramine was significantly higher than that of sertraline in the central plus peripheral and peripheral effect groups (p <0.01).

CONCLUSIONS

Differences in potency of the peripheral inhibitory effects of the selective serotonin re-uptake inhibitors and clomipramine may contribute to their differential effects on delaying ejaculatory latency in patients with premature ejaculation.

Serotonin reuptake inhibitor fluoxetine decreases arteriolar myogenic tone by reducing smooth muscle [Ca2+]i

Previous studies showed that the serotonin reuptake inhibitor (SSRI) antidepressant fluoxetine (Prozac) dilates skeletal muscle and cerebral arterioles independent of the endothelium. We hypothesized that fluoxetine affects the contractile activity of arteriolar smooth muscle by interfering with Ca2+ signaling pathways. The effects of fluoxetine on pressure-induced tone of isolated rat skeletal muscle arterioles (approximately 110 microm) were investigated by videomicroscopy. Changes in smooth muscle [Ca2+]i were measured simultaneously by the fura-2 ratiometric method. Elevation of intraluminal pressure (from 20 to 120 mm Hg) increased (by approximately 20%) the smooth muscle calcium fluorescence ratio (R(Ca)) and resulted in a significant myogenic constriction (approximately 40%). Fluoxetine and nifedipine significantly decreased R(Ca) (by approximately 30%) and abolished pressure-induced arteriolar tone (EC50, 3.1 x 10(-6) and 6.0 x 10(-9) M, respectively). Constrictions to the L-type Ca2+ channel opener Bay K 8644 also were inhibited and abolished by increasing doses of fluoxetine (3 x 10(-6) and 10(-5) M, respectively). In the presence of 10(-5) M fluoxetine, a concentration that elicited submaximal (approximately 80%) dilation, elevation of extracellular Ca2+ concentration (from 2.5 to 15 mM) normalized R(Ca) and restored arteriolar myogenic tone. Thus, fluoxetine reduces [Ca2+]i and tone of arteriolar smooth muscle, likely by interfering with Ca2+ entry. We speculate that the "calcium antagonist" effect of fluoxetine may be an additional element in the therapeutic actions of this drug.

Inhibition of voltage-gated calcium channels by fluoxetine in rat hippocampal pyramidal cells

Fluoxetine, an antidepressant which is used world-wide, is a prominent member of the class of selective serotonin re-uptake inhibitors. Recently, inhibition of voltage-gated Na(+) and K(+) channels by fluoxetine has also been reported. We examined the effect of fluoxetine on voltage-gated calcium channels using the patch-clamp technique in the whole-cell configuration. In hippocampal pyramidal cells, fluoxetine inhibited the low-voltage-activated (T-type) calcium current with an IC(50) of 6.8 microM. Fluoxetine decreased the high-voltage-activated (HVA) calcium current with an IC(50) between 1 and 2 microM. Nifedipine and omega-conotoxin GVIA inhibited the HVA current by 24% and 43%, respectively. Fluoxetine (3 microM), applied in addition to nifedipine or omega-conotoxin, further reduced the current. When fluoxetine (3 microM) was applied first neither nifedipine nor omega-conotoxin attenuated the remaining component of the HVA current. This observation indicates that fluoxetine inhibits both L- and N-type currents. In addition, fluoxetine inhibited the HVA calcium current in carotid body type I chemoreceptor cells and pyramidal neurons prepared from prefrontal cortex. In hippocampal pyramidal cells high K(+)-induced seizure-like activity was inhibited by 1 microM fluoxetine; the mean burst duration was shortened by an average of 44%. These results provide evidence for inhibition of T-, N- and L-type voltage-gated calcium channels by fluoxetine at therapeutically relevant concentrations.

Effect of fluoxetine on contractile activity of pregnant rat uterine rings

OBJECTIVE

We sought to compare the effects of fluoxetine, imipramine, and nortriptyline on spontaneous and serotonin-activated contractile activity of the uterine rings from midterm and term pregnant rats.

STUDY DESIGN

Uterine rings from timed-pregnant Sprague-Dawley rats on day 14 (midgestation) and day 22 (term gestation) were used for isometric tension recording. Responses to cumulative concentrations of fluoxetine, imipramine, nortriptyline, and serotonin in the absence and presence of the monoamine reuptake inhibitors were studied.

RESULTS

Neither of the monoamine reuptake inhibitors significantly influenced spontaneous contractile activity, whereas the concentration-dependent increase in activity induced by serotonin was inhibited in rings from both midterm and term pregnant rats.

CONCLUSIONS

The reported increase in preterm delivery in women receiving fluoxetine during the third trimester cannot be explained by a direct effect on uterine contractility.

Fluoxetine dilates isolated small cerebral arteries of rats and attenuates constrictions to serotonin, norepinephrine, and a voltage-dependent Ca(2+) channel opener

BACKGROUND AND PURPOSE

Recent clinical observations question that the antidepressant effect of fluoxetine (Prozac) can be explained solely with serotonin reuptake inhibition in the central nervous system. We hypothesized that fluoxetine affects the tone of vessels and thereby modulates cerebral blood flow.

METHODS

A small branch of rat anterior cerebral artery (195+/-15 microm in diameter at 80 mm Hg perfusion pressure) was isolated, cannulated, and pressurized (at 80 mm Hg), and changes in diameter were measured by videomicroscopy.

RESULTS

Fluoxetine dilated small cerebral arteries with an EC(50) of 7.7+/-1.0x10(-6) mol/L, a response that was not affected by removal of the endothelium or application of 4-aminopyridine (an inhibitor of aminopyridine-sensitive K(+) channels), glibenclamide (an inhibitor of ATP-sensitive K(+) channels), or tetraethylammonium (a nonspecific inhibitor of K(+) channels). The presence of fluoxetine (10(-6) to 3x10(-5) mol/L) significantly attenuated constrictions to serotonin (10(-9) to 10(-5) mol/L) and norepinephrine (10(-9) to 10(-5) mol/L). Increasing concentrations of Bay K 8644 (a voltage-dependent Ca(2+) channel opener, 10(-10) to 10(-6) mol/L) elicited constrictions, which were markedly reduced by 2x10(-6) and 10(-5) mol/L fluoxetine, whereas 3x10(-5) mol/L fluoxetine practically abolished the responses.

CONCLUSIONS

Fluoxetine elicits substantial dilation of isolated small cerebral arteries, a response that is not mediated by endothelium-derived dilator factors or activation of K(+) channels. The finding that fluoxetine inhibits constrictor responses to Ca(2+) channel opener, as well as serotonin and norepinephrine, suggests that fluoxetine interferes with the Ca(2+) signaling mechanisms in the vascular smooth muscle. We speculate that fluoxetine increases cerebral blood flow in vivo, which contributes to its previously described beneficial actions in the treatment of mental disorders.

Serotonin reuptake inhibitor, fluoxetine, dilates isolated skeletal muscle arterioles. Possible role of altered Ca2+ sensitivity

1. Inhibitors of serotonin reuptake in the central nervous system, such as fluoxetine, may also affect the function of vascular tissues. Thus, we investigated the effect of fluoxetine on the vasomotor responses of isolated, pressurized arterioles of rat gracilis muscle (98 +/- 4 microns in diameter at 80 mmHg perfusion pressure). 2. We have found that increasing concentrations of fluoxetine dilated arterioles up to 155 +/- 5 microns with an EC50 of 2.5 +/- 0.5 x 10(-6) M. 3. Removal of the endothelium, application of 4-aminopyridine (4-AP, an inhibitor of aminopyridine sensitive K+ channels), or use of glibenclamide (an inhibitor of ATP-sensitive K+ channels) did not affect the vasodilator response to fluoxetine. 4. In the presence of 10(-6), 2 x 10(-6) or 10(-5) M fluoxetine noradrenaline (NA, 10(-9)-10(-5) M) and 5-hydroxytryptamine (5-HT, 10(-9)-10(-5)M)-induced constrictions were significantly attenuated resulting in concentration-dependent parallel rightward shifts of their dose-response curves (pA2 = 6.1 +/- 0.1 and 6.9 +/- 0.1, respectively). 5. Increasing concentrations of Ca2+ (10(-4) 3 x 10(-2) M) elicited arteriolar constrictions (up to approximately 30%), which were markedly reduced by 2 x 10(-6)M fluoxetine, whereas 10(-5)M fluoxetine practically abolished these responses. 6. In conclusion, fluoxetine, elicits substantial dilations of isolated skeletal muscle arterioles, a response which is not mediated by 4-AP- and ATP-sensitive K+ channels or endothelium-derived dilator factors. The findings that fluoxetine had a greater inhibitory effect on Ca2+ elicited constrictions than on responses to NA and 5-HT suggest that fluoxetine may inhibit Ca2+ channel(s) or interfere with the signal transduction by Ca2+ in the vascular smooth muscle cells.

Effect of venlafaxine hydrochloride in different preparations of isolated guinea-pig and rat organ tissues

A study was undertaken to know better the effects of venlafaxine hydrochloride on the responses of isolated rat vas deferens to noradrenaline and dopamine, those of isolated rat uterus to serotonin and histamine, and those of isolated guinea-pig ileum to acetylcholine and histamine. Venlafaxine hydrochloride increased the response of rat vas deferens to noradrenaline but not to dopamine. Venlafaxine did not alter the response of rat isolated uterus to serotonin. In rat uterus, venlafaxine did not modify the response to histamine but was able to increase it in guinea-pig ileum. An anticholinergic effect was observed with the lowest concentration tested. Although venlafaxine is a selective serotonine reuptake inhibitor in the central nervous system, serotonin uptake was not seen in the rat uterus. The anticholinergic effects observed in the present study might be consistent with some of the side-effects associated with venlafaxine.