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PubMed1996

Effect of dopexamine hydrochloride on sympathetic neuroeffector transmission in rabbit isolated pulmonary artery.

The effects of dopexamine hydrochloride on sympathetic neuroeffector transmission were studied in rabbit isolated pulmonary artery. Short-term exposure of dopexamine (10(-8) x 10(-7) M) and cocaine (10(-6)-3 x 10(-5) M), but not desipramine (3 x 10(-9)-3 x 10(-7) M), to the artery enhanced the contractions evoked by electrical-field stimulation. Corticosterone (4 x 10(-5) M), corticosterone (4 x 10(-5) M) plus cocaine (3 x 10(-8) M), but not cocaine (3 x 10(-5) M), attenuated the enhancement seen with dopexamine. High concentrations of dopexamine (10(-5)-3 x 10(-5) M), cocaine (10(-4) M), and desipramine (10(-6)-10(-5) M) decreased the stimulation-evoked contractions. Dopexamine (10(-7)-3 x 10(-5) M), but neither cocaine nor desipramine, caused an increase in resting tension that waned with time. Corticosterone (4 x 10(-5) M), but not cocaine (3 x 10(-5) M), attenuated the increase in resting tension. Propranolol (10(-6) M) did not alter the enhancing and inhibitory effects of dopexamine. A single concentration (10(-7) and 10(-6) M) of either dopexamine or desipramine caused a time-dependent biphasic response as regards the repetitive stimulation-evoked contractions of pulmonary artery: initial enhancement followed by inhibition. The inhibitory effect of dopexamine (10(-6) M) and desipramine (3 x 10(-6) M) seen after prolonged exposure was almost irreversible and partially reversible, respectively, by washing the preparations with drug-free salt solution. Cocaine caused a monophasic steady-state response: either enhancement (10(-5) M) or inhibition (2 x 10(-4) M). In both cases, the onset was rapid. The reduction caused by cocaine (2 x 10(-4) M) and by prazosin (10(-9) M) was fully reversed. Dopexamine (10(-5) M) antagonized competitively the contractions evoked by noradrenaline (3 x 10(-9)-10(-4) M). It is concluded that (1) the dopexamine-induced enhancement of neurogenic contractions is not due to either inhibition of neuronal and extraneuronal uptake of noradrenaline or an agonist action on prejunctional beta 2-adrenoceptors; (2) that the dopexamine-induced inhibition of stimulation-evoked contraction is due to an inhibition of postjunctional alpha 1-adrenoceptors; and (3) that the dopexamine-induced increase in resting tension is due to its metabolite methyldopexamine.

Animals↗
PubMed1991

Does regional norepinephrine spillover represent local sympathetic activity?

Regional spillover of norepinephrine (NE), based on isotope dilution and single-compartment steady-state kinetics, is considered one of the best parameters for estimating organ sympathetic activity. However, the effects of local changes in clearance of NE on the spillover have not yet been investigated. We studied local NE kinetics and clearance in the forearm of 10 healthy subjects using intra-arterial infusions of NE, tritiated NE, the neuronal uptake inhibitor desipramine, and tyramine, which competes with NE for the neuronal uptake carrier. Before and during complete blockade of neuronal uptake by desipramine the venous concentration-time curves for tritiated NE and for NE released by tyramine were biexponential, consistent with the presence of (at least) two compartments for circulating tritiated NE and for locally released NE. The time constants for tyramine-induced release of NE and, in the same subjects during desipramine infusion, for tritiated NE were almost equal at the same level of forearm blood flow. This argues against possible diffusion or transport differences for NE to and from the circulation and the synapse. The regional intrinsic clearance capacity (a measure of the maximal ability of an organ to irreversibly remove drug by all pathways in the absence of any flow limitations) for NE decreased in the forearm by 65% (p less than 0.01) during neuronal uptake blockade by desipramine; the forearm clearance decreased by 59% (p less than 0.001), whereas the spillover rate of NE increased from 33 +/- 5 to 63 +/- 11 pmol.min-1 (p less than 0.05). Nitroprusside-induced increments in blood flow increased the spillover of NE from 18 +/- 4 to 35 +/- 6 pmol.min-1 (p less than 0.01); the clearance of circulating NE also increased (by 58%, p less than 0.05), and the intrinsic clearance capacity remained unchanged. This demonstrates that regional spillover of NE is markedly influenced by local changes in clearance and flow. The new parameter plasma appearance rate of NE is proposed. Although also derived from isotope dilution, this parameter may better approximate the regional entry of NE into the blood pool than spillover. This is corroborated by the nonsignificant changes of plasma appearance rate of NE during our desipramine and nitroprusside infusions.

Adult↗
PubMed1970

Guanethidine and related agents. 3. Antagonism by drugs which inhibit the norepinephrine pump in man.

Antagonism of the antihypertensive action of guanethidine by the tricyclic antidepressants, desipramine and protriptyline, has been demonstrated in controlled studies. These antidepressants also prevent the effect of the related ring-substituted guanidinium adrenergic neuron blockers, bethanidine and debrisoquin. That the rise in blood pressure when desipramine is added to guanethidine therapy is not due simply to a pressor action of the two drugs in combination was demonstrated by the lack of an increase in blood pressure when guanethidine was added to desipramine therapy. Investigations were conducted to determine whether antagonism of guanethidine's clinical effect could result from blockade by the tricyclic antidepressants of the norepinephrine pump in the adrenergic neuron membrane, thereby preventing the uptake of guanethidine into the neuron by this pump. Like guanethidine, the indirectly acting pressor amine, tyramine, enters the neuron via the norepinephrine pump. Desipramine, protriptyline, and amitriptyline in clinical doses all were found to block the pressor action of tyramine while potentiating the pressor effect of norepinephrine. The amino acid, methyldopa, does not enter the neuron via the norepinephrine pump, and its antihypertensive action is not altered by concomitant administration of tricyclic antidepressants. It is concluded from the evidence in this investigation together with the results of previous studies in experimental animals that clinical doses of desipramine-like drugs inhibit the norepinephrine pump in the peripheral adrenergic neuron in man and thereby prevent uptake of guanethidine to its site of action.

Antidepressive Agents↗
PubMed1989

[Effects in animal models of depression of lisuride alone and upon coadministration with antidepressants].

Effects of lisuride, a central dopamine and serotonin agonist of the ergot type, in animal models of depression were investigated in comparison with those of desipramine, mianserin and rolipram. Lisuride, like desipramine and mianserin, inhibited reserpine-induced hypothermia in mice (0.5-5.0 mg/kg, i.p.) and suppressed muricide in olfactory bulbectomized rats (ED50 = 0.16 mg/kg, i.p.) in a dose-dependent manner. The anti-muricidal effect was slightly enhanced by the repeated administration of 0.25 mg/kg lisuride. Lisuride (0.05-0.25 mg/kg, i.p.), like desipramine, dose-dependently reduced the duration of immobility in rats forced to swim, and this effect was antagonized by haloperidol. The reduction of immobility time was enhanced by the repeated administration of lisuride; at the same time, the ambulation in rats increased. Furthermore, the immobility-reducing effects of desipramine and rolipram were markedly enhanced by the co-administration of a low dose of lisuride (0.025 mg/kg, i.p.), which by itself had no effect on the immobility time. These results indicate that lisuride may be useful for the treatment of depression and indicate that a low dose of lisuride may enhance the clinical effectiveness of antidepressants such as desipramine.

Agonistic Behavior↗
PubMedDate not supplied

Plasma concentration and clinical effect in imipramine treatment of childhood enuresis.

The relationship between steady-state plasma concentraton and clinical effect of imipramine in the treatment of nocturnal enuresis was studied in 22 hospitalised children. After 1 week on placebo the children were given imipramine in a fixed dose of about 1 mg/kg for 3 weeks. The enuresis frequency decreased significantly from the placebo to the first week on imipramine, but then no further improvement was observed. There was a significant correlation between steady-state plasma concentration of desipramine or imipramine + desipramine and the reduction in enuresis frequency during imipramine treatment. The optimum effect was obtained when steady-state levels of imipramine + desipramine were above 60 microgram/L; i.e. the effective concentration in enuresis is 3 to 4 times lower than in antidepressive therapy. Dose- and weight-corrected, steady-state plasma concentration of imipramine and desipramine were not significantly different from those previously observed in younger adults. In 1 child, a transient rise in imipramine and desipramine concentration was seen during a period with fever and bacterial infection.

Adolescent↗
PubMedDate not supplied

Influence of antidepressant drugs on macrophage cytotoxic activity in rats.

The aim of the study was to evaluate the in vivo and in vitro effects of antidepressant drugs on cytotoxic activity of rat spleen macrophages. In the in vivo experiment, rats were injected subcutaneously with two different doses (2 or 10 mg/kg) of desipramine, fluvoxamine and fluoxetine. The drugs were given once, for 2, 4 or 8 weeks. In the in vitro experiment, spleen macrophages were cultured with three different concentrations of desipramine (3.75, 0.75, or 0.075 mM), fluvoxamine (3.14, 0.62, or 0.062 mM), and fluoxetine (3.23, 0.64, or 0.064 mM) for 72 h. The cytotoxic activity of macrophages was evaluated by measuring the lysis of ((51)Cr) chromate-labelled P-815 target cells. In the in vivo experiment, a single dose of fluvoxamine (2 and 10 mg/kg) and fluoxetine (10 mg/kg) significantly decreased macrophage cytotoxic activity. Fluvoxamine (2 and 10 mg/kg), fluoxetine (10 mg/kg) and desipramine (10 mg/kg) administrated for 14 days also decreased macrophage cytotoxic activity. Twenty-eight day treatment with desipramine (2 and 10 mg/kg) decreased macrophage cytotoxic activity. Desipramine, fluvoxamine and fluoxetine given for 56 days did not affect macrophage cytotoxic activity. In the in vitro experiment, antidepressant drugs did not affect the cytotoxic activity of macrophages. The results of the study indicate that the effects of antidepressant drugs on macrophage cytotoxic activity depend on the drug type, dose and duration of the treatment.

Animals↗
PubMed1988

Pharmacological and behavioral treatments of cocaine dependence: controlled studies.

The cocaine epidemic has stimulated novel treatments aimed at reducing relapse to this extremely addicting drug. After detoxification and standard treatment, former cocaine users continue to exhibit strong cocaine craving and physiological changes when presented with cocaine-related stimuli. Because these conditioned responses may increase the risk of relapse, a new treatment has been developed to extinguish such responses. The extinction process, consisting of repeated presentations of cocaine-related stimuli until the stimuli gradually lose their ability to evoke conditioned responses, is integrated into a comprehensive rehabilitation program. Cocaine dependence is often combined with opiate dependence. Desipramine has been added to methadone maintenance in an attempt to reduce dependence on both substances. Methadone impedes catabolism of desipramine so that relatively low doses of desipramine may produce antidepressant effects and possibly reduce the desire to use cocaine. Preliminary evidence from a placebo-controlled study of desipramine in combination with methadone suggests that desipramine produces significant improvements in psychological functioning, but its effects on reduction of cocaine use are less dramatic.

Animals↗
PubMed1980

Potentiation of responses to adrenergic nerve stimulation in isolated rat atria during chronic tricyclic antidepressant administration.

Several weeks of tricyclic antidepressant administration are required to effectively reverse depression. To determine whether there are adaptive changes in andrenergic nerve function which correspond to the clinical onset of antidepressant action, the endogenous norepinephrine content, [3H]norepinephrine uptake and retention, responses to exogenous norepinephrine and the release of norepinephrine during field stimulation were studied using left atrial strips isolated from rats treated with either acutely or chronically with tricyclic antidepressants. Desipramine, nortriptyline, chlorimipramine and iprindole were administered to rats, 10 mg/kg i.p., twice daily. After 14 days of drug administration, the responses to field stimulation were potentiated markedly by all four tricyclics. In contrast, 1 day of tricyclic treatment had only slight potentiating effects. When phenoxybenzamine, 10(-7) M, was added to the organ bath in order to block the inhibitory presynaptic alpha receptor, the responses of control atria and atria from rats treated for 1 day with desipramine were potentiated but those of atria treated for 21 days with desipramine were not potentiated. The development of presynaptic alpha receptor subsensitivity during chronic tricyclic administration would explain these findings. Other possible explanations were also investigated. The uptake and retention of [3H]norepinephrine was markedly inhibited to a similar degree of either 1 or 14 days of desipramine or nortriptyline administration. One day of chlorimipramine treatment decreased the amount of [3H]norepinephrine taken up and retained by left atrial strips, and after 14 days of treatment decreased the amount further. In contrast, neither 1 nor 14 days of iprindole administration had any effect on the uptake and retention of [3H]norepinephrine. These data indicate that the potentiation of the responses to field stimulation cannot be explained by the inhibition of norepinephrine uptake. The inotropic response to exogenous norepinephrine was not altered by any duration of administration of any of the four tricyclics studied. Furthermore, the endogenous norepinephrine content of atria did not change after as many as 21 days of desipramine administration. The present results indicate that the potentiation of the effects of adrenergic nerve transmission during chronic tricyclic administration is the result of an increase in norepinephrine release which occurs due to the development of presynaptic alpha receptor subsensitivity. The time course of development of presynaptic receptor subsensitivity corresponds well with the onset of clinical activity of these drugs.

Animals↗
PubMed1994

Dopamine receptor mediated antidepressant action of B-HT 920 in mice.

Possible involvement of dopaminergic (DAergic) system in forced swimming-induced immobility (despair behaviour) was investigated in mice. B-HT 920 (0.05 and 0.1 mg/kg), a post-synaptic DAergic agonist, produced a dose dependent reduction in immobility period, which was sensitive to blockade by haloperidol (0.5 mg/kg) and sulpiride (100 mg/kg). This effect was also blocked by alpha 2 antagonist yohimbine (5 mg/kg). SKF 38393 (5 mg/kg), a D1-DA agonist potentiated the action of B-HT 920. Reserpinization (2 mg/kg, 24 hr prior) produced despair immobility in mice. When a low dose of B-HT 920 (0.05 mg/kg) was given to reserpinized animals, the duration of immobility period was further increased. But on the other hand, a higher dose (0.1 mg/kg) of it reduced reserpine-induced immobility. Desipramine (5 and 10 mg/kg), elicited a dose dependent reduction in the immobility period, which was sensitive to blockade by sulpiride (100 mg/kg). Desipramine (10 mg/kg) showed a diphasic response in combination with B-HT 920, i.e., a potentiation of the response due to a low dose of B-HT 920 (0.05 mg/kg) and an antagonism of the response due to a higher dose of B-HT 920 (0.1 mg/kg), respectively. SKF 38393 (5 mg/kg), potentiated the action of desipramine (5 mg/kg). SKF 38393 (5 mg/kg) further potentiated the action of desipramine (5 mg/kg) and B-HT 920 (0.05 mg/kg). These observations suggests that B-HT 920 reduces behavioural immobility by DAergic mechanism and desipramine also modulates D2-DA receptors in its anti-depressant action.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1996

In vivo effects of the simultaneous blockade of serotonin and norepinephrine transporters on serotonergic function. Microdialysis studies.

The effects of the blockade of serotonin (5-HT) and norepinephrine (NE) transporters on extracellular 5-HT (5-HText) have been examined using in vivo microdialysis in conscious rats. Locally infused, imipramine increased 5-HText dose-dependently in raphe nuclei and frontal cortex. The potency was identical (ED50 11 microM), although greater elevations were noted in the raphe nuclei (e.g., 74.5 +/- 16.9 vs. 41.1 +/- 4.5 fmol/fraction in the frontal cortex at 33 microM imipramine). The i.p. administration of imipramine at 4, 10 and 20 mg/kg increased 5-HText dose-dependently in the frontal cortex to concentrations as high as 390% of basal values. The lowest dose of imipramine significantly increased 5-HText in the raphe, but not in the frontal cortex (187 vs. 120% of basal values, respectively), but higher doses did not cause substantially greater increases in the raphe. The lowest dose affected 5-HText in a manner comparable to 1 mg/kg of the selective 5-HT reuptake inhibitors citalopram and fluvoxamine. The noradrenergic system may participate in the cortical elevations seen after 10 and 20 mg/kg of imipramine, because 10 mg/kg of desipramine significantly increased 5-HText in the frontal cortex, but not the raphe nuclei, of fluoxetine-treated rats (from 8.6 +/- 1.4 to 13.3 +/- 1.9 fmol/fraction; prefluoxetine values: 4.3 +/- 0.6 fmol/fraction, n = 11). Desipramine alone (10 mg/kg i.p.) did not modify 5-HText in the frontal cortex. The elevation induced by desipramine in fluoxetine-treated rats does not seem to involve changes in the activation of alpha-2 adrenoceptors, as it was still present in rats pretreated with 0.2 mg/kg i.p. of RX-821002, a selective antagonist of alpha-2 adrenoceptors. Moreover, clonidine, an alpha-2 adrenoceptor agonist, significantly reduced 5-HText in fluoxetine-treated rats when infused locally in the cortex, but it did not modify the effects of the systemic administration of desipramine, providing a further indication that alpha-2 heteroreceptors in 5-HT terminals do not participate in the effects of desipramine. When given for 2 weeks, 4 mg/kg day of imipramine significantly elevated 5-HText in the frontal cortex (from 7.7 +/- 1.2 to 20.0 +/- 5.8 fmol/fraction), but not in the raphe nuclei. These results are consistent with previous data suggesting that low doses of antidepressants with serotonergic action enhance 5-HText in the frontal cortex only after repeated treatment. The elevations noted in the frontal cortex after the higher doses of imipramine may reflect the involvement of the noradrenergic system.

Adrenergic Uptake Inhibitors↗
PubMedDate not supplied

Cardiac sympathetic nerve function assessed by [131I]metaiodobenzylguanidine after ischemia and reperfusion in anesthetized dogs.

BACKGROUND: Accumulation of 131I-labeled metaiodobenzylguanidine ([131I]MIBG), a radiolabeled norepinephrine analog, is reduced in infarcted myocardium, suggesting loss of cardiac sympathetic nerve viability. Histopathologic studies, however, indicate that the nerve endings ae morphologically intact. Experiments were therefore designed to determine the mechanism of reduced MIBG accumulation. METHODS AND RESULTS: Desipramine, a specific blocker or neuronal norepinephrine reuptake, was used to separate the portions of total myocardial [131I]MIBG accumulation attributable to neuronal and nonneuronal uptake mechanisms. Sixteen dogs underwent circumflex coronary artery occlusion for 60 minutes followed by a 5-hour reperfusion. [131I]MIBG was injected intravenously 1 hour after reperfusion. The left ventricle was removed and incubated in triphenyltetrazolium chloride to identify infarcted and viable myocardium within the zone at risk. Preliminary studies in sham-operated dogs showed that pretreatment with desipramine (5 mg/kg) reduced [131I]MIBG accumulation 4 hours after injection to 38.9% of untreated controls. Chemical sympathectomy by topical phenol resulted in a similar decrease in [131I]MIBG accumulation (to 45.7% of normal), and desipramine did not produce further inhibition of [131I]MIBG accumulation over that produced by phenol alone, indicating that the inhibitory effect of desipramine on neuronal accumulation of [131I]MIBG was essentially complete. In dogs undergoing ischemia-reperfusion, myocardial samples from infarcted and viable postischemic areas showed 64.5% +/- 11.85 and 84.7% +/- 9.1% of normal [131I]MIBG activity, respectively (both, p < 0.01 vs normal area, n = 9). With desipramine pretreatment (n = 7), accumulation of [131I]MIBG decreased in all areas. Neuronal accumulation was reduced uniformly in infarcted, viable postischemic, and normal areas by 30% to 35% compared with sham-operated controls. In contrast, nonneuronal accumulation was only 39.3% in infarcted areas and 84.6% in viable postischemic areas compared with normal areas, and these decreases accounted entirely for the reduced total [131I]MIBG accumulation. CONCLUSIONS: Reduced [131I]MIBG accumulation in infarcted myocardium after 60 minutes of ischemia and 5 hours of reperfusion is attributable to a deficit in nonneuronal accumulation and not to decreased accumulation by sympathetic nerves.

3-Iodobenzylguanidine↗
PubMed2000

Tricyclic and related drugs for nocturnal enuresis in children.

BACKGROUND: Enuresis (bedwetting) is a socially unacceptable and stressful condition which affects around 15-20% of five year olds, and up to 2% of young adults. Although there is a high rate of spontaneous remission, the social, emotional and psychological costs to the children can be great. OBJECTIVES: To assess the effects of tricyclic and related drugs on nocturnal enuresis in children, and to compare them with other interventions. SEARCH STRATEGY: The following electronic databases were searched: MEDLINE to June 1997; AMED; ASSIA; BIDS; BIOSIS Previews (1985-1996); CINAHL; DHSS Data; EMBASE (1974 to June 1997); PsycLIT and SIGLE. Organisations, manufacturers, researchers and health professionals concerned with enuresis were contacted for information. The reference sections of obtained studies were also checked for further trials. Date of the most recent search: July 1997. SELECTION CRITERIA: All randomised trials of tricyclic and related drugs for nocturnal enuresis in children were included in the review. Trials were eligible for inclusion if: children were randomised to receive tricyclics compared with placebo, other drugs or other conservative interventions for nocturnal bedwetting; participants with organic causes for their bedwetting were excluded; and baseline assessments of the level of bedwetting were provided. Trials focused solely on daytime wetting were excluded. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed the quality of the eligible trials, and extracted data. MAIN RESULTS: Twenty two randomised trials, involving 1100 children treated with tricyclic or related drugs, met the inclusion criteria. The quality of many of the trials was poor. Only single trials compared tricyclic or related drugs with each other, other drugs, desmopressin, alarms or other behavioural interventions. Treatment with tricyclic drugs (such as imipramine, amitriptyline, viloxazine, clomipramine and desipramine but not mianserin) were associated with a reduction of about one wet night per week while on treatment (eg using imipramine, WMD -0.99, 95% CI -1.27 to -0.71). Children were almost five times more likely to achieve 14 dry nights with the drugs (eg using imipramine, RR = 4.99, 95% CI 2.4 to 10.40). Desmopressin and tricyclics appeared equally effective while on treatment, but this effect was not sustained after treatment stopped. There was no detectable difference between imipramine and alarms while on treatment, but afterwards those who had used alarms had one fewer wet night per week (WMD 1.03, 95% CI 0. 19 to 1.87). REVIEWER'S CONCLUSIONS: Treatment with tricyclic drugs (imipramine, amitriptyline, viloxazine, clomipramine and desipramine but not mianserin) was associated with a reduction of about one wet night per week while on treatment, but long term effectiveness is unknown. Desmopressin and tricyclics appeared equally effective while on treatment, but this effect was not sustained after treatment stopped. Alarms may be more effective in the long term. Comparisons between drug and behavioural treatments are needed, and should include relapse rates after treatment is finished.

Antidepressive Agents, Tricyclic↗
PubMed1992

Effects of chronic administration and withdrawal of antidepressant agents on circadian activity rhythms in rats.

Experimental and clinical studies indicate that clinical depression may be associated with disturbances of circadian rhythms. To explore the interaction between circadian rhythmicity, behavioral state, and monoaminergic systems, the present study investigated the effects of chronic administration and withdrawal of the following antidepressant agents on circadian wheel-running rhythms of laboratory rats: a) moclobemide, a reversible and selective monoamine oxidase (MAO) type A inhibitor; b) Ro 19-6327, a selective MAO type B inhibitor; c) desipramine, a preferential norepinephrine reuptake inhibitor; d) clomipramine and e) fluoxetine, both serotonin reuptake inhibitors; and f) levoprotiline, an atypical antidepressant whose biochemical mechanism is still unknown. Wheel-running activity rhythms were studied in three inbred strains of laboratory rats (ACI, BH, LEW) under constant darkness (DD). Two of these inbred strains (BH and LEW) show profound abnormalities in their circadian activity rhythms, namely, a reduced overall level of activity and bimodal or multimodal activity patterns. Chronic treatment with moclobemide and desipramine consistently increased the overall level, as well as the circadian amplitude, of the activity rhythm. Furthermore, the abnormal activity pattern of the LEW strain was changed into a unimodal activity pattern like that of other laboratory rats. The free-running period tau was slightly shortened by moclobemide and dramatically shortened by desipramine. Effects of moclobemide and desipramine treatment on overall activity level and duration were reversed shortly after termination of treatment, whereas long aftereffects were observed for the free-running period. All other substances tested had no systematic effects on the activity rhythms of any of the strains. The fact that moclobemide and desipramine altered the period, amplitude, and pattern of circadian activity rhythms is consistent with the hypothesis that monoaminergic transmitters play a significant role in the neuronal control of behavioral state and circadian rhythmicity. Although the present study found that some antidepressives affect parameters of circadian rhythmicity, it could not demonstrate a common effect of all classes of antidepressives.

Animals↗
PubMed2004

Synergistic interaction between ketoconazole and several antidepressant drugs with allopregnanolone treatments in ovariectomized Wistar rats forced to swim.

This article was aimed to investigate the interest of the combination allopregnanolone plus ketoconazole in depression with the time-sampling method in the forced swimming task. Dose-response curves for fluoxetine (0.5, 1.0 or 2.0 mg/kg, twice day, during 2 weeks; i.p.), desipramine (0.5, 1.0 or 2.14 mg/kg, twice a day, during 2 weeks; i.p.), ketoconazole (6.25, 12.5, 25.0 and 37.5 mg/kg, once a day, during 2 weeks; i.p.) and allopregnanolone (0.5, 1.5, 2.0 mg/kg; once a day, during 2 weeks; s.c.) were established. Fluoxetine (1.0 mg/kg, p < 0.05; 2.0 mg/kg, p < 0.05) or ketoconazole (25.0 mg/kg, p < 0.05; 37.5 mg/kg, p < 0.05) produced antidepressant-like behavioral changes in swimming, highlighting a serotonergic mechanism while desipramine (1.0 mg/kg, p < 0.05; 2.14 mg/kg, p < 0.05) or allopregnanolone (1.5 mg/kg, p < 0.05; 2.0 mg/kg, p < 0.05) increased climbing behavior highlighting noradrenergic or dopaminergic effects. Subthreshold doses of fluoxetine (p < 0.05), desipramine (p < 0.05) or ketoconazole (p < 0.05) synergized with subthreshold doses of allopregnanolone and reduced immobility by increasing climbing. In conclusion, fluoxetine, desipramine, ketoconazole and allopregnanolone produced differential antidepressant-like actions in ovariectomized rats forced to swim. Ketoconazole, fluoxetine or desipramine synergized with allopregnanolone.

Analysis of Variance↗
PubMed2003

Effects of ketamine on exocytotic and non-exocytotic noradrenaline release.

To characterise ketamine-induced sympathomimetic action, we examined the effects of ketamine on in vivo cardiac sympathetic nerve endings function. Using adult cats given anaesthesia with pentobarbital, dialysis probes were implanted in the left ventricular myocardium and dialysate noradrenaline (NA) concentrations were measured as an indicator of NA output at the cardiac sympathetic nerve endings. Ketamine was locally administered through the dialysis probe, and dialysate NA responses were obtained in the following conditions. (1) In the resting state, ketamine (10 mM) increased dialysate NA concentration. This increase in dialysate NA was not altered by addition of omega-conotoxin GVIA (N-type Ca(2+) channel blocker) or desipramine (membrane NA uptake blocker). (2) Sympathetic activation by electrical stimulation of the stellate ganglia (ES-SG; exocytotic NA release): ES-SG caused an increase in dialysate NA, which was further augmented by addition of desipramine. During co-administration of desipramine and ketamine, dialysate NA response to ES-SG was smaller than with desipramine alone. Further, there was no significant difference in the dialysate NA response to ES-SG between ketamine and ketamine + desipramine. These data suggested that both exocytosis and NA uptake function were impaired by ketamine. (3) Non-exocytotic NA release by ouabain: ouabain caused increases in dialysate NA. These increases in dialysate NA were suppressed by ketamine, which impaired the membrane outward NA transport evoked by ouabain. We conclude that ketamine impaired exocytotic and non-exocytotic NA release. However, ketamine spontaneously evoked NA efflux that was independent of exocytosis and insensitive to NA transporter.

Animals↗
PubMed2006

Acid ceramidase but not acid sphingomyelinase is required for tumor necrosis factor-{alpha}-induced PGE2 production.

Sphingolipids are well established effectors of signal transduction downstream of the tumor necrosis factor (TNF) receptor. In a previous study, we showed that the sphingosine kinase/sphingosine 1-phosphate (S1P) pathway couples TNF receptor to induction of the cyclooxygenase 2 gene and prostaglandin synthesis (Pettus, B. J., Bielawski, J., Porcelli, A. M., Reames, D. L., Johnson, K. R., Morrow, J., Chalfant, C. E., Obeid, L. M., and Hannun, Y. A. (2003) FASEB J. 17, 1411-1421). In this study, the requirement for acid sphingomyelinase and sphingomyelin metabolites in the TNFalpha/prostaglandin E(2) (PGE(2)) pathway was investigated. The amphiphilic compound desipramine, a frequently employed inhibitor of acid sphingomyelinase (ASMase), blocked PGE(2) production. However, the action of desipramine was independent of its action on ASMase, since neither genetic loss of ASMase (Niemann-Pick fibroblasts) nor knockdown of ASMase using RNA interference affected TNFalpha-induced PGE(2) synthesis. Further investigations revealed that desipramine down-regulated acid ceramidase (AC), but not sphingosine kinase, at the protein level. This resulted in a time-dependent drop in sphingosine and S1P levels. Moreover, exogenous administration of either sphingosine or S1P rescued PGE(2) biosynthesis after desipramine treatment. Interestingly, knockdown of endogenous AC by RNA interference attenuated cyclooxygenase 2 induction by TNFalpha and subsequent PGE(2) biosynthesis. Taken together, these results define a novel role for AC in the TNFalpha/PGE(2) pathway. In addition, the results of this study warrant careful reconsideration of desipramine as a specific inhibitor for ASMase.

Animals↗
PubMed1990

The chemotherapy of rodent malaria. XLV. Reversal of chloroquine resistance in rodent and human Plasmodium by antihistaminic agents.

The inherent blood schizontocidal activities of five antihistaminic compounds, cyproheptadine hydrochloride (CYP), ketotifen hydrogen fumarate (KET), pizotyline hydrogen maleate (PIZ), azatadine maleate (AZAT) and loratadine (LOR) were examined against the following organisms: chloroquine-sensitive (CS) Plasmodium berghei and chloroquine-resistant (CR) P. yoelii ssp. NS in mice; and CS Tak 9 clone 96 and CR K1 strain of P. falciparum in vitro. Chloroquine, verapamil and desipramine were used as comparison standards. CYP, KET, PIZ were active against the CS strain in vivo with ED90 levels between 20 and 30 mg kg-1 (given sc daily for four days). They were slightly more active against the CR strain. AZA was active, but much less so than the other compounds. LOR, verapamil and desipramine were inactive in vivo at the doses tested. Against CS P. falciparum in vitro, all five antihistaminics and desipramine were active at EC50 concentrations ranging from about 50-80 mumol l-1, while verapamil was only active at 175 mumol l-1. Against the CR strain of this parasite, CYP, PIZ and LOR were slightly more active than against the CS strain, but KET, AZAT, desipramine and verapamil were significantly less active. The action of all these compounds in combination with chloroquine was then examined both in vivo and in vitro. The ability of verapamil and desipramine to reverse chloroquine resistance in vitro was confirmed, but only a low level of reversal was seen with these compounds in vivo. However, CYP, KET, PIZ and AZAT produced a marked reversal of chloroquine resistance both in vivo and in vitro. The implications of these observations in relation to further laboratory and clinical research are discussed.

Animals↗
PubMed1986

Activation and desensitization of presynaptic alpha 2-adrenoceptors after inhibition of neuronal uptake by antidepressant drugs in the rat vas deferens.

The isolated field-stimulated vas deferens of the rat (0.1 Hz, 3 ms, 30-40 V) was used to study the relationship between the in vivo inhibition of neuronal uptake of noradrenaline (NA) by cyclic antidepressant drugs and the subsequent activation/desensitization of presynaptic alpha 2-adrenoceptors. Receptor activation was indirectly measured by quantifying the ability of each drug to inhibit basal twitch responses after their acute administration. Receptor desensitization was also indirectly measured by quantifying the ability of the drugs to reduce the inhibitory effects of selective alpha 2-adrenoceptor agonists on the electrically-induced twitch responses after their long-term administration. The acute in vivo administration of desipramine and other antidepressants (0.5-10 mg kg-1; i.p.; 2 h) resulted in dose-dependent inhibitions of the basal twitch responses which were rapidly reversed to control values by idazoxan (10-5 M). In vitro, desipramine and other antidepressants also inhibited in a concentration-dependent manner (10(-9)-10(-5) M) the twitch responses. In rats pretreated 12 h earlier with reserpine (1 mg kg-1; i.p.) or oxypertine (4 mg kg-1; i.p.), desipramine (10 mg kg-1; 2 h) did not induce inhibition of the basal twitch responses or it induced a smaller effect, respectively. For the various antidepressants the degree of inhibition of the basal twitch responses (desipramine greater than protriptyline greater than nortriptyline greater than maprotiline = imipramine greater than amitriptyline greater than viloxazine greater than iprindole much greater than zimelidine) was highly correlated (r = 0.914) with the potency for blockade of [3H]-NA uptake into rat brain synaptosomes. Clonidine and xylazine inhibited in a concentration-dependent manner (10(-9)-10(-6) M) the twitch responses. The long-term (7-14 days) administration of antidepressants or cocaine (10 mg kg-1, i.p.) resulted in significant decreases in sensitivity to clonidine or xylazine. Short-term (3 days) treatment with desipramine did not reduce the sensitivity to clonidine. The results indicate that the acute in vivo inhibition of NA neuronal uptake by antidepressants leads to the activation (through endogenous NA) of presynaptic inhibitory alpha 2-adrenoceptors which results in inhibition of the twitch responses. In contrast, prolonged in vivo inhibition of NA reuptake is followed by a slow desensitization process of the same receptors which results in a reduction of sensitivity to clonidine.

Animals↗