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PubMed1985

Changes in mouse brain serotonin turnover following chronic imipramine administration.

Mice were injected daily for 2 weeks with saline, tryptophan or p-chlorophenylalanine, alone or in combination with the tricyclic antidepressant imipramine. Serotonin turnover in several brain regions was determined by the accumulation of serotonin after pargyline and 5-hydroxyindoleacetic acid after probenecid. Both methods agreed closely. Imipramine tended to depress serotonin turnover. This effect was more marked in hypothalamus, which has high serotonin activity, and was much less in cerebellum, which has low serotonin activity. Chronic imipramine treatment completely abolished the increase in serotonin turnover induced by tryptophan, but had no effect on serotonin turnover in mice treated with p-chlorophenylalanine, which itself reduced serotonin activity.

Animals↗
PubMed1989

The effects of imipramine, mianserin and trazodone on the chronotropic, inotropic and coronary vascular responses in the isolated perfused rat heart.

1. The cardiovascular effects of the tricyclic antidepressant imipramine and two second generation antidepressants mianserin, a tetracyclic, and trazodone, a triazolopyridine derivative, were investigated in the isolated perfused rat heart. 2. Imipramine caused cardiac slowing and a negative inotropic effect at 2.5 microM after 30 min of perfusion. Conversely mianserin and trazodone had no effect on heart rate at 5 microM with inotropic state remaining above control values after 30 min of perfusion. 3. Varying effects on coronary flow, which appear to correlate well with the documented receptor actions of each drug, were demonstrated. Imipramine caused a decrease in coronary flow at 1.25 and 2.5 microM, followed by an increase at 10 microM. Mianserin decreased coronary flow at all concentrations between 1 and 20 microM. Trazodone elicited a marked elevation in coronary flow over the dose range of 2.5 to 250 microM. 4. The results in this model suggest that although the second generation agents appear to cause less cardiodepression all three agents elicit quantitatively different coronary vascular responses.

Animals↗
PubMed1991

Involvement of protein kinase C in the mechanism of in vitro effects of imipramine on generation of second messengers by noradrenaline in cerebral cortical slices of the rat.

Imipramine did not significantly inhibit the noradrenaline or isoproterenol-induced cyclic AMP accumulation in rat cerebral cortical slices, but inhibited the potentiation of this response by protein kinase C activator, a phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate. In low concentrations (0.1-1 microM) it prevented the inhibitory effect of the phorbol ester on accumulation of inositol phosphate induced by noradrenaline, while in higher concentrations it inhibited the response by itself. Imipramine did not bind to beta-adrenoceptors but was an effective blocking agent of alpha 1-adrenoceptors (Ki = 38.1 nM). The data suggest that imipramine acts within the noradrenergic cyclic AMP generating system on two targets: inhibiting protein kinase C and blocking the alpha 1-adrenoceptor; both actions may reduce the alpha-adrenoceptor potentiation of beta-adrenoceptor-mediated cyclic AMP generation.

Adenylyl Cyclases↗
PubMed1987

The neuroendocrine effects of oral imipramine.

The release of growth hormone, prolactin and cortisol following oral imipramine was studied in nine fit young men. Imipramine 100 mg, but not 40 mg, led to reliable rises in the circulating levels of all three hormones in the majority of subjects. These responses are likely due to the enhancement of central noradrenergic and serotonergic function as a result of reuptake inhibition. The safety, sensitivity and reliability of these responses make imipramine 100 mg orally a potentially valuable neuroendocrine challenge test.

Administration, Oral↗
PubMed1981

Thyrotropin releasing hormone potentiates the effects of imipramine on brain serotonergic system.

Daily administration of thyrotropin-releasing hormone (TRH) (20 mg/kg) for 10 days in 2 equally divided doses increased 5-hydroxytryptamine and/or 5-hydroxyindoleacetic acid levels in certain brain areas. Chronic imipramine treatment (10 mg/kg) for 10 days significantly decreased the levels of brain 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. When TRH was administered concurrently with imipramine (10 mg/kg), this neuropeptide significantly potentiated the effects of imipramine on lowering of endogenous levels of 5-hydroxytryptamine (striatum, hypothalamus) and 5-hydroxyindoleacetic acid (striatum, midbrain, pons-medulla). Our data provide a possible neurochemical basis for the reported potentiation of tricyclic antidepressant action by TRH.

Animals↗
PubMed1995

Second-order derivative spectrophotometric assay for imipramine hydrochloride and diazepam in pure admixtures and in dosage forms.

The determination of imipramine HCl and diazepam in tablets by derivative spectrophotometry is described. The drugs in combined preparations have been quantified using the second-order derivative spectra of their solutions in 0.1 M HCl. The method has been applied to pure drug mixtures as well as commercial preparations and was found to be precise and reproducible. Compliance of Beer's Law was observed in the concentration range of 10-70 micrograms ml-1 for imipramine HCl and 2-8 micrograms ml-1 for diazepam. Lower limits of detection at the 95% confidence level were 1.96 micrograms ml-1 for imipramine HCl and 0.21 microgram ml-1 for diazepam.

Diazepam↗
PubMed1987

Reduction of (3H)-imipramine binding sites on platelets of conduct-disordered children.

Binding characteristics of tritiated imipramine on blood platelets were determined in daytime hospitalized prepubertal children who had mixed diagnoses of conduct disorder (CD) plus attention deficit disorder hyperactivity (ADDH) and in inpatient adolescents who had a history of aggressive behavior. The number of (3H)-imipramine maximal binding sites (Bmax) was significantly lower in the prepubertal patient group of CD plus ADDH; the dissociation constant (Kd) was not significantly different. There were significant negative correlations between Bmax and the Externalizing or Aggressive factors of the Child Behavior Checklist when the CD plus ADDH prepubertal patients were combined with their matched controls and within the adolescent inpatient group. We propose that a decreased platelet imipramine binding Bmax value, as an index of disturbed presynaptic serotonergic activity, is not specific to depression and may be used as a biologic marker for the lack of behavioral constraint in heterogeneous. populations of psychiatric patients.

Adolescent↗
PubMed1994

Kinase inhibitors compete with imipramine for binding and inhibition of serotonin transport.

Effects of kinase inhibitors and activators on the binding of tritiated imipramine and inhibition of serotonin uptake were tested in platelets. The majority of compounds inhibited specific [3H]imipramine binding and serotonin uptake with affinities similar to those reported for their action on protein kinases themselves. Many of these compounds are derivatives with modified naphthalenesulfonamide or isoquinolinesulfonamide structures, which appear to compete directly with imipramine for binding to the serotonin transporter. This is of great importance for studies involving kinase regulation since at these concentrations, the inhibitors and activators were previously thought to interact virtually exclusively with protein kinases.

Binding, Competitive↗
PubMed1994

Adverse effects associated with the short-term treatment of panic disorder with imipramine, alprazolam or placebo.

Side effects play a significant role in the selection of drugs to be used in panic disorder/agoraphobia whose polyphobic symptomatology often includes a suspiciousness about taking drugs and a fear of undesired side effects which may lead to the refusal of treatment. The safety, side effects and patients' acceptance of alprazolam and imipramine versus placebo were evaluated in 1168 subjects with panic disorder/agoraphobia who had been enrolled in the second phase of the Upjohn World Wide Panic Study. Side effects that worsened over baseline to a greater extent with alprazolam than with imipramine and placebo were sedation, fatigue/weakness, memory problems, ataxia and slurred speech. In the imipramine group blurred vision, tachycardia/palpitations, insomnia, sleep disturbance, excitement/nervousness, malaise, dizziness/faintness, headache, nausea/vomiting and decrease in appetite were worse than in the other groups. In the placebo group the anxious symptoms were most prominent. The highest level of compliance was shown in the alprazolam-treated group and the lowest in the placebo-treated group. Strong predictors of side effects were not observed. If a side effect profile is known, it will be easier for a clinician to choose the right drug and the appropriate management by taking into account compliance, safety and efficacy in each patient under treatment. Further information about side effects in long-term maintenance treatment would be of great clinical pertinence in ensuring safety and enhancing patients' quality of life.

Adolescent↗
PubMed2005

Hypoxia activates glycogen synthase kinase-3 in mouse brain in vivo: protection by mood stabilizers and imipramine.

BACKGROUND: Glycogen synthase kinase-3 (GSK3), which is primarily regulated by an inhibitory phosphorylation of an N-terminal serine, has been implicated as contributing to mood disorders by the finding that it is inhibited by the mood stabilizer lithium. METHODS: This study tested if the antidepressant imipramine or the mood stabilizers lithium and sodium valproate regulated pathophysiological serine-dephosphorylation of GSK3 caused by hypoxia in mouse brain in vivo. RESULTS: Hypoxia caused rapid serine-dephosphorylation of both isoforms of GSK3, GSK3beta and GSK3alpha, in mouse cerebral cortex, hippocampus, and striatum. Pretreatment of mice with imipramine, sodium valproate, or lithium attenuated hypoxia-induced serine-dephosphorylation of GSK3beta and GSK3alpha in all three brain regions. CONCLUSIONS: These results demonstrate that imipramine and mood stabilizers are capable of blocking pathophysiologically induced serine-dephosphorylation of GSK3, supporting the hypothesis that stabilization of serine-phosphorylation of GSK3 contributes to their therapeutic effects.

Animals↗
PubMed2006

Different relevance of inactivation and F468 residue in the mechanisms of hEag1 channel blockage by astemizole, imipramine and dofetilide.

The relevance of a point mutation at the C-terminal end of the S6 helix (F468) and the introduction of C-type inactivation in the blockage of hEag1 channels by astemizole, imipramine and dofetilide was tested. C-type inactivation decreased block by astemizole and dofetilide but not imipramine, suggesting different binding sites in the channel. F468C mutation increased IC(50) for astemizole and imipramine but in contrast to HERG channels, only slightly for dofetilide. Together with measurements on recovery of blocking, our observations indicate that the mechanism of hEag1 blockage by each of these drugs is different, and suggest relevant structural differences between hEag1 and HERG channels.

Astemizole↗
PubMed2004

Effects of chronic activity wheel running and imipramine on masculine copulatory behavior after olfactory bulbectomy.

We examined the effects of chronic activity wheel running and imipramine administration on appetitive behavior after olfactory bulbectomy (OBX). Male Long-Evans rats were randomly assigned to the following conditions using a 2 x 2 x 2 design: (1) bilateral OBX or sham surgery, (2) voluntary activity wheel running or sedentary home cage, and (3) daily imipramine or saline injections. After 21 days of treatment, animals underwent behavioral testing for copulatory activity and sucrose preference. Bulbectomized animals exhibited decrements in copulatory performance and reductions in sucrose intake compared to sham animals. Within the bulbectomized groups, imipramine-treated rats either did not copulate or had reduced ejaculation frequencies. However, activity wheel running attenuated the copulatory deficits induced by OBX. The findings encourage studies of physical activity and male sexual dysfunction among depressed men being treated by pharmacotherapy.

Animals↗
PubMed2004

Effects of triiodothyronine on 5-HT(1A) and 5-HT(1B) autoreceptor activity, and postsynaptic 5-HT(1A) receptor activity, in rat hypothalamus: lack of interaction with imipramine.

Triiodothyronine (T3) is effective in both augmenting and accelerating the therapeutic response to antidepressant drugs, especially tricyclics, and there is evidence from both human and animal studies that it acts on serotonergic neurotransmission. In this work we examined the effects of T3 alone and together with imipramine on 5-HT levels in the hypothalamus and on 5-HT(1A) and 5-HT(1B) autoreceptor sensitivity, using in vivo microdialysis in the rat. The effects of T3 on postsynaptic 5-HT(1A) receptor activity in the hypothalamus were also determined using a neuroendocrine challenge procedure. T3 administered daily at 20 microg/kg s.c. for 2 weeks reduced the sensitivity of 5-HT(1A) autoreceptors which control 5-HT release, as measured by the effect of 8-OH-DPAT to decrease 5-HT in the hypothalamus, and also the sensitivity of hypothalamic 5-HT(1B) receptors as measured by the effect of the 5-HT(1B) receptor agonist CP 93129 to decrease 5-HT release. Imipramine at 10 mg/kg daily for 4 weeks by osmotic minipump reduced 5-HT(1A) autoreceptor activity, as measured by the effect of 8-OH-DPAT in the hypothalamus, but the combination of T3 and imipramine given for 2 weeks did not affect either 5-HT(1A) or 5-HT(1B) autoreceptor activity. T3 at 20 microg/kg s.c. given daily for 1 week also reduced the sensitivity of postsynaptic 5-HT(1A) receptors in the hypothalamus, as measured by injection of 8-OH-DPAT and determination of the plasma ACTH and corticosterone responses. Animals which received T3 for 7 days showed a dose-dependent reduction in plasma free T4 levels but no change in total T3 levels. We conclude that while T3 alone affects both presynaptic and postsynaptic components of the serotonergic system, these effects may not be responsible for the therapeutic acceleration action seen with a combination of a tricyclic drug and T3.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

Reduced platelet tritium-labeled imipramine binding sites in women with premenstrual syndrome.

OBJECTIVE: We studied the possible role of serotonergic systems in the cause of premenstrual affective symptoms. STUDY DESIGN: The binding of tritium-labeled imipramine to platelets is thought to parallel central nervous system binding and to indicate serotonergic activity. We measured platelet tritium-labeled imipramine binding sites in the follicular and luteal phases in 12 controls and in 9 women with well-documented late luteal phase dysphoric disorder. In statistical analyses we used repeated measures analysis of variance, with Student-Newman-Keuls and Duncan's one-tailed t tests, and Pearson's r. RESULTS: The values of subjects with late luteal phase dysphoric disorder were lower than those of controls (F [1,39] = 5.13, p = 0.03). Both follicular and luteal phase level were lower in subjects with late luteal phase dysphoric disorder but reached statistical significance only in the follicular phase. CONCLUSION: Lower platelet tritium-labeled imipramine binding in women with late luteal phase dysphoric disorder supports the hypothesis that alteration of central serotonergic systems may contribute to premenstrual dysphoric symptoms.

Adult↗
PubMed1998

Gauging the effectiveness of extended imipramine treatment for panic disorder with agoraphobia.

BACKGROUND: Imipramine has proven efficacy for panic disorder. This study assesses the net effectiveness of systematic, open imipramine treatment in a homogenous sample of panic disorder patients with agoraphobia. METHODS: One hundred and ten consecutive patients with DSM-III-R moderate to severe panic disorder with agoraphobia were treated with a fixed regimen of imipramine 2.25 mg/kg/day for 24 weeks. No instructions or encouragement for self-directed exposure to phobic situations or other coping strategies with panic or fear were given. Assessments were conducted at the end of the 2-week placebo run-in and at weeks 8, 16, and 24 of treatment. RESULTS: Overall, 53% had a marked and stable response. Most measures revealed that substantial improvement continued beyond week 8 of treatment. Treatment success was accompanied with significant improvements in anxiety sensitivity, dysphoric mood, and functional well-being. CONCLUSIONS: These results provide a clinically relevant reference with which to compare the effectiveness of alternative treatments in providing nearly complete symptom remission in patients with primary panic disorder with agoraphobia.

Adolescent↗
PubMed1987

Upregulation of imipramine binding and serotonin uptake by estradiol in female rat brain.

This report describes the effect of chronic estradiol treatment on the serotonin transporter in the female rat brain. Both [3H]imipramine binding and [3H]serotonin uptake increased by 20-30% in the frontal cortex and hypothalamus of ovariectomized rats after 12 days of 17 beta-estradiol treatment. No differences were observed in the binding and uptake parameters as a function of the rats' estrous cycle or in untreated ovariectomized rats, as compared to controls. Estradiol in vitro, inhibits [3H]imipramine binding as well as serotonin uptake in rat brain and human platelets. Like serotonin, estradiol decreases the dissociation rate in vitro of [3H]imipramine from its binding site in a dose-dependent manner.

Animals↗
PubMed1987

In vivo or in vitro exposure to imipramine reduces alpha 2-adrenoceptor-mediated inhibition of cyclic AMP production in rat brain cerebral cortical slices.

The effect of in vivo or in vitro exposure to imipramine on alpha 2-adrenoceptor-mediated inhibition of cAMP production in rat brain slices was examined. Chronic administration (10 mg/kg once daily for 14 or 21 days) of imipramine or in vitro exposure (100 microM, 60 min) to the antidepressant significantly reduced the ability of UK-14,304, an alpha 2-adrenoceptor agonist, to inhibit forskolin-stimulated cAMP accumulation in cerebral cortical slices. This reduction was due to a decrease in the maximal response to the alpha 2-adrenergic agonist rather than to a decrease in its potency. Besides yielding a rapid and direct method for studying the effect of imipramine on brain receptors in vitro, these findings provide biochemical evidence in support of the notion that this drug, and perhaps other antidepressants, modifies alpha 2-adrenoceptor function in the central nervous system.

Adrenergic alpha-Agonists↗
PubMed1997

Imipramine demethylation in vivo: impact of CYP1A2, CYP2C19, and CYP3A4.

OBJECTIVE: To further substantiate the role of CYP1A2 and CYP3A4 for the N-demethylation in vivo. At least three different P450s appear to be responsible for the N-demethylation of imipramine to desipramine in vivo: CYP1A2, CYP2C19, and CYP3A4. The role of CYP2C19 in this regard is well documented, but for the two other P450s the evidence is either indirect or based on in vitro studies. METHODS: Phenotypic tests for imipramine N-demethylation, CYP1A2 (caffeine testing), CYP2C19 (mephenytoin and chloroguanide [proguanil] testing), and CYP3A4 (hydrocortisone and quinidine testing) were carried out in 32 healthy young Danes; all were poor (n = 31) or extremely slow extensive metabolizers (n = 1) of sparteine. RESULTS: By exclusion of the insignificant log-transformed variables, multiple regression analysis for In (desipramine/imipramine) showed that only in (mephenytoin S/R) correlated (p = 0.013; r2 = 0.19). For in (2-hydroxydesipramine/2-hydroxyimipramine) we found that in (mephenytoin S/R) and in (4-chlorophenylbiguanide/chloroguanide) correlated (p = 0.001; r2 = 0.41). CONCLUSION: We did not find in vivo evidence of either CYP1A2 or CYP3A4 activity in the N-demethylation of imipramine. This could be due in part to inadequate CYP1A2 and CYP3A4 in vivo function tests.

Adult↗