Chronic Administration Of Clomipramine Research Articles

Altered expression of 5-HT1A receptors in adult rats induced by neonatal treatment with clomipramine

Chronic administration of clomipramine (CMI) to neonatal rats produces behaviors that resemble a depressive state in adulthood. Dysfunctions in the activity of the central nervous system's serotonergic function are important in understanding the pathophysiology of depression. The serotonin system is implicated in major depression and suicide and is negatively regulated by somatodendritic 5-HT1A autoreceptors. Desensitization of 5-HT1A autoreceptors is implicated in the long latency of some antidepressant treatments. Alterations in 5-HT1A receptor levels are reported in depression and suicide. In this study, we analyzed the effect of neonatal administration of CMI on the activity of 5-HT1A receptors, both pre- and post-synaptically, by administering an agonist of 5-HT1A receptors, 8-OH-DPAT, and then subjecting the rats to the forced swimming test (FST) a common procedure used to detect signs of depression in rats. Also measured were levels of the mRNA expression of 5-HT1A receptors in the dorsal raphe (DR), the hypothalamus and the hippocampus. Wistar rats were injected twice daily with CMI at doses of 15mgkg−1 or saline as vehicle (CON) via s.c. from postnatal day 8 for 14days. At 3–4months of age, one set of rats from each group (CON, CMI) was evaluated for the effect of a selective agonist to the 5-HT1A receptor subtype, 8-OH-DPAT, by testing in the FST. Also determined was the participation of the pre- or post-synaptic 5-HT1A receptor in the antidepressant-like action of 8-OH-DPAT. This involved administering an inhibitor of tryptophan hydroxylase, parachlorophenylalanine (PCPA), and pretreatment with 8-OH-DPAT before the FST test and to evaluate the rectal temperature and locomotor activity. The expression of the mRNA of the 5-HT1A receptors was examined in the dorsal raphe nucleus, the hypothalamus and the hippocampus using the semi-quantitative RT-PCR method. The results from this study corroborate that neonatal treatment with clomipramine induces a pronounced immobility in the FST when animals reach adulthood, manifested by a significant decrease in swimming behavior, though counts of climbing behavior were not modified. This effect was similar in magnitude when 8-OH-DPAT was administered to CON group. Furthermore, the administration of 8-OH-DPAT induces a significant and similar increase in rectal temperature and locomotor activity in both the CON as in the CMI group. Neonatal treatment with CMI resulted in a significant decrease in the expression of the mRNA of the 5-HT1A receptors in the DR (% more than vehicle) in adulthood. In the case of the postsynaptic receptors located in the hypothalamus and hippocampus, neonatal treatment with CMI induced a significant increase in the mRNA expression of the 5-HT1A receptors. These data suggest that neonatal treatment with CMI induces a downregulation of the mRNA of the 5-HT1A autoreceptors in the DR, and an increment in the expression of the postsynaptic 5-HT1A receptors. The results after the administration of PCPA and 8-OH-DPAT on FST, rectal temperature and locomotor activity for both groups suggest that the function of postsynaptic receptors remains unchanged. All together these data show that the depressive behavior observed in adulthood in this animal model may be associated with long-term alterations in the expression of the mRNA of the 5-HT1A receptors.

Apparent down-regulation of rat brain mu- and kappa-opioid binding sites labelled with [3H]cycloFOXY following chronic administration of the potent 5-hydroxytryptamine reuptake blocker, clomipramine.

This study examined the effect of chronic clomipramine administration on opioid mu- and kappa-binding sites. Clomipramine (5 mg kg-1 day-1) or saline was administered to rats via osmotic minipumps for 3 days or 28 days. Lysed-P2 brain membranes were prepared and preincubated for 60 min without (control membranes) or with 1 microM of the mu-selective acylating agent, 2-(4-ethoxybenzyl)-1-diethylaminoethyl-5-isothiocyanatobenzimid azole-HC1 (BIT), to deplete membranes of mu-binding sites. [3H]6-Desoxy-6 beta-fluoronaltrexone ( [3H]cyclo FOXY) was used to label mu and kappa-binding sites. Weighted nonlinear least squares analysis of cycloFOXY binding surfaces permitted determination of the Kd and Bmax values of mu- and kappa-binding sites in control and treated rats. Subacute (3 days) administration of rats with clomipramine had no significant effect on [3H]cycloFOXY binding. Chronic (28 days) administration of clomipramine produced a small (approximately 10%) but statistically significant decrease in the Bmax. These findings are discussed in reference to other studies that have examined the effect of chronic antidepressant administration on opioid receptors, and speculate that the endogenous opioid systems may play a role in obsessive-compulsive disorder.

Regional distribution of clomipramine and desmethylclomipramine in rat brain and peripheral organs on chronic clomipramine administration

The tricyclic antidepressant (TCA) clomipramine has been widely used in psychiatry for over 40 years. More recently, its therapeutic potential as an antineoplastic drug has been identified. However, there are no prior data on regional distribution in the brain of clomipramine and its primary metabolite (desmethylclomipramine) after chronic oral administration. The aim of this study was to determine the concentrations of clomipramine and desmethylclomipramine in different rat-brain regions and to compare those with levels in plasma and peripheral organs after chronic oral treatment of Sprague Dawley rats (15 mg/kg) for 14 days. The levels of both parent TCA and metabolite were analysed by high-performance liquid chromatography in six brain regions (cortex, hypothalamus, hippocampus, striatum, brainstem and cerebellum), five peripheral organs and in plasma. Our data show that the cerebral cortex had the highest concentration of clomipramine (2.9 microg/mg), with successively lower concentrations in the hypothalamus, striatum, cerebellum, hippocampus and brainstem. Of the peripheral organs, the lungs and liver, had the highest levels of clomipramine, while in the heart, only the metabolite was detected. The plasma concentration (0.17 microg/ml or 0.48 microM) was comparable to that in the hippocampus and cerebellum (approximately 0.20 microg/mg). The differential distribution of clomipramine in different brain regions and the regional variation in clomipramine to desmethylclomipramine ratios have implications for the use of clomipramine in psychiatry and neuro-oncology.

Modeling panic attacks

The isomorphism of dorsal periaqueductal gray-evoked defensive behaviors and panic attacks was appraised in the present study. Thresholds of electrically induced immobility, trotting, galloping, jumping, exophthalmus, micturition and defecation were recorded before and after acute injections of anxiolytic, anxiogenic and antidepressant drugs. Antidepressant effects were further assessed 24h after injections of 7–14- and 21-day treatments. Chronic administration of clomipramine (CLM, 5–10mg/kg) a clinically effective antipanic drug increased the thresholds of immobility (24%), trotting (138%) galloping (75%), jumping (45%) and micturition (85%). The 21-day treatment with fluoxetine (FLX, 1mg/kg) virtually abolished galloping without changing the remaining responses. Galloping thresholds were also increased by 5mg/kg acute injections of CLM (19%) and FLX (25%). In contrast, chronically administered maprotiline (10mg/kg), a noradrenaline (NE) selective reuptake inhibitor, selectively increased the thresholds of immobility (118%). Diazepam (1.8mg/kg) and midazolam (MDZ, 2.5mg/kg) failed in attenuating the somatic defensive responses. Yet, the sedative dose of MDZ (5mg/kg) attenuated immobility. The panicogenic drug, pentylenetetrazole (50mg/kg), markedly decreased the thresholds of galloping (−51%) and micturition (−66%). These results suggest that whereas immobility is a NE-mediated attentional response, galloping is the panic-like behavior best candidate.

Chronic clomipramine alters presynaptic 5-HT 1B and postsynaptic 5-HT 1A receptor sensitivity in rat hypothalamus and hippocampus, respectively

Clomipramine is a tricyclic antidepressant drug with a high affinity for the serotonin (5-HT) uptake site or transporter. Electrophysiological experiments have provided evidence that repeated administration of clomipramine induces an increase in the sensitivity of postsynaptic 5-HT 1A receptors in the hippocampus. We have studied the effects of clomipramine, administered to rats at a dose of 10 mg/kg/day for 28 days by osmotic minipumps, on presynaptic 5-HT 1A and 5-HT 1B autoreceptors in the hypothalamus, and on postsynaptic 5-HT 1A receptors in the hippocampus, by using in vivo microdialysis to measure 5-HT and cyclic adenosine monophosphate (cAMP) levels. Postsynaptic 5-HT 1A receptor sensitivity in the hypothalamus was determined by means of a neuroendocrine challenge procedure. Although the sensitivity of presynaptic 5-HT 1A autoreceptors, as measured by the effect of a subcutaneous (s.c.) injection of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 0.2 mg/kg or 50 μg/kg) to reduce 5-HT levels, did not change, there was a reduction in sensitivity of presynaptic 5-HT 1B receptors, as measured by the effect of an injection of the 5-HT 1B/1D antagonist GR 127935 (5 mg/kg, s.c.) to increase 5-HT levels. This effect probably accounted for the increase in basal 5-HT levels observed in the hypothalamus after chronic clomipramine administration. Postsynaptic 5-HT 1A receptor sensitivity in the hippocampus, measured by the effect of 8-OH-DPAT to increase cAMP levels in the dialysate, was increased after chronic clomipramine. Animals that had received daily intraperitoneal injections of 10 mg/kg clomipramine for 28 days did not show a change in postsynaptic 5-HT 1A receptor sensitivity in the hypothalamus as measured by the ability of 8-OH-DPAT (50 μg/kg, s.c.) to stimulate secretion of corticosterone. Taken together with the results of previous experiments involving the cerebral cortex, these in vivo results show that chronic clomipramine exerts effects on both pre- and postsynaptic serotonin receptors, but that these effects are highly region-specific.

Effects of Clomipramine Administration on Syrian Hamster Circadian System and Behavior

The aim of the present work is to discuss the available data on neonatal and adult antidepressant treatment in relation to animal models of depression and serotonergic modulation of the circadian system, with a particular emphasis on our own published and unpublished work on the effects of clomipramine (a serotonin reuptake inhibitor) on the Syrian hamster circadian behavior. Neonatal clomipramine treatment (15 mg/kg from postnatal days 8 to 21) significantly augmented the amplitude of the wheel running rhythm, as well as delayed its acrophase and increased the time to reentrain after a 6-h phase advance of the light-dark cycle. Neonatally clomipramine-treated hamsters had a shorter circadian period than saline-treated animals under constant light - but not under constant dark- conditions, exhibited decreased phase advances after light pulses applied at late subjective night and greater phase advances after i.p. administration of the 5-HT1A-receptor agonist 8-OH-DPA at midday. These animals also exhibited more locomotor activity than controls, but did not display the typical circadian variation in anxiety-related behavior, as measured in a plus-maze paradigm. They also showed an increased 5-HIAA/5-HT ratio in hypothalamus and midbrain raphe, while 5-HT content was decreased in frontal cortex and anterior hypothalamic areas. Since drugs linked to the serotonergic system are able to modify the circadian system, we decided to test whether acute and chronic clomipramine administration in adulthood was able to change: a) the phase of free running activity rhythms; (b) light-induced phase shifts, and (c) hypothalamic 5-HT turnover. Acute clomipramine injection had a phase-dependent effect on the free running activity rhythm, with phase advances at CT 0-8 being significantly higher than at CT 8-16. Pretreatment with clomipramine inhibited phase advances in response to light pulses when applied at CT 19 while phase delays at CT 14 remained unaffected. This acute treatment also decreased 5-HT turnover in the SCN at both CTs. In contrast, chronic clomipramine administration potentiated light-induced phase advances, without changes in period, amplitude or central 5-HT turnover. Taken together, these data support the view that clomipramine, as other antidepressant drugs, can affect the expression of the circadian rhythmicity in Syrian hamsters, possibly through serotonergic mechanisms in the case of acute treatments, and more complex behavioral interaction in the case of neonatal and chronic treatments.

Chronic clomipramine administration reverses NMDA-evoked decreases in dopamine release in the raphe nuclei

The effect of acute or chronic treatment with the antidepressant clomipramine (CIM) on basal and N-methyl- d-aspartate (NMDA) evoked release of dopamine (DA) in rat raphe has been studied using microdialysis. Acute injection of CIM (10 or 20 mg/kg) caused a decrease in raphe DA release, as did infusion of NMDA (25–100 μM) into this region. When NMDA infusion was preceded by a single acute injection of CIM no differences between NMDA and NMDA plus CIM treated groups was observed. Chronic (15 day) treatment with CIM caused a dose-dependent increase in basal extracelluar DA. In addition the effect of infusing NMDA into the raphe on DA release was markedly reduced or abolished. This suggests that adaptive changes occur in NMDA receptor function during treatment with CIM.

Long-term effects on serotonin transporter mRNA expression of chronic neonatal exposure to a serotonin reuptake inhibitor

Chronic administration of clomipramine or other serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors to neonatal rats produces behaviours that resemble a depressive state in the adult animal, and this model is therefore regarded as a putative animal model of depression. Alterations in the activity of the central 5-HT system are important in understanding the pathophysiology of depression, and therefore, we examined whether this model was associated with changes in the expression of 5-HT 1A receptor, 5-HT 1B receptor, and 5-HT transporter mRNA in the dorsal raphe nucleus and the hippocampus. Wistar rats were injected twice daily with the serotonin reuptake inhibitors clomipramine and 5-chloro-1-[3-(dimethylamino)propyl]-1-(4-fluoro-phenyl)-1,3-dihydroiso-benzofurane, hydrochloride (code Lu 10-134-C) at doses of 15 mg kg −1 or vehicle i.p. from postnatal day 8 for 14 days. Groups of rats ( n=10) were either killed the day after the last injection or left undisturbed for 69 days before they were killed. The expression of 5-HT transporter, 5-HT 1A receptor, and 5-HT 1B receptor mRNA was examined in the dorsal raphe nucleus and in the CA1 of the hippocampus by means of quantitative in situ hybridisation histochemistry. Both compounds resulted in an increase in 5-HT transporter mRNA expression (40% more than vehicle) in the dorsal raphe nucleus the day after the last injection (postnatal day 22). A small but significant increase in 5-HT 1B receptor mRNA expression in the CA1 was seen after clomipramine, but not after Lu 10-134-C, probably reflecting clomipramine's affinity for both the 5-HT and noradrenaline transporters as well as for a number of monoamine receptor sites. Levels of 5-HT 1A receptor mRNA were unchanged. In contrast, 5-HT transporter mRNA expression in the dorsal raphe nucleus was significantly decreased in the adult after neonatal treatment with either of the two drugs compared to vehicle. No changes in 5-HT 1A receptor and 5-HT 1B receptor mRNA expression were observed in any of the regions examined in these animals. The results show that the persistent depressive behaviour previously shown in this model is also associated with changes in the expression of 5-HT transporter mRNA. This long-term alteration in gene expression may result from disturbances in 5-HT neurotransmission in the brain of the neonatal animals.

Changes of serotonin and catecholamines are related to pharmacokinetic alterations of cloimpramine in rat brain

When rats received a single i.p. injection of clomipramine (20 mg/kg), clomipramine and desmethylclomipramine were rapidly distributed into the brain and their concentrations were markedly higher in the brain than in the serum, while the oncentration of the metabolite in the brain was much lower than that of clomipramine. Chronic administration of clomipramine gadually increased the concentrations of the metabolite in both serum and brain, but did not significantly change those of clomipramine. The levels of serotonin (5-HT), norepinephrine (NE), dopamine (DA) and their metabolitcs in the brain were compared with the concentrations of clomipramine and desmethylclomipramine at different times. The levels of 5-HT, NE. DA, dihydroxyphenylacetic acid(DOPAC) and homovaanilic acid(HVA)in the brain did not appear to be affected by changes in the concentrations of the drug and metabolite. The level of 5-hydroxyindole acetic acid (5-HIAA) was reduced following clomipramine injection and the reduced level was maintained during chronic treatment. Chronic treatment for more than 7 days increased the 3-methoxy-4-hydroxyphenylglycol (MHPG) level with no alteration of NE level. This elevation appeared to be induced by desmethylclomipramine.

Chronic administration of clomipramine prevents the increase in serotonin and noradrenaline induced by chronic stress

The effects of chronic clomipramine administration (15 mg/kg daily for 23 days) on changes in serotonin (5-hydroxytryptamine, 5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and noradrenaline (NA) induced by chronic stress have been studied in the rat brain. Chronic stress increased 5-HT in midbrain, pons and hippocampus, 5-HIAA in frontal cortex, midbrain, pons and hippocampus, and NA in midbrain and striatum. Chronic clomipramine significantly decreased the levels of 5-HT in most regions. In hypothalamus, hippocampus and perhaps in frontal cortex this effect possibly reflects decreased synthesis caused by an action on presynaptic 5-HT receptors. However, in midbrain, pons and striatum decreased 5-HT could not be attributed to a decrease in its synthesis since 5-HIAA also increased. This drug treatment also reduced NA in all regions except the striatum. Nevertheless, conclusions on NA synthesis or turnover cannot be drawn since only NA levels were measured. When administered concurrently, chronic clomipramine prevented the increases in 5-HT, 5-HIAA and NA produced by chronic stress. These results are in good accordance with previous findings showing that chronic antidepressant treatment also prevented behavioural disturbances induced by chronic stress.

Modification of the antinociceptive effect of morphine by acute and chronic administration of clomipramine in mice

The antinociception effect of clomipramine and the combination of clomipramine and morphine was evaluated using the constant temperature hot plate test, the increasing temperature hot plate test and the formalin test in mice. Both a single dose of clomipramine (10 mg/kg) given intraperitoneally (i.p.) and chronic clomipramine treatment (10 mg/kg/day, i.p., for 7 days) induced antinociception. When morphine (5 mg/kg), given subcutaneously (s.c.), and clomipramine were combined, an increased antinociceptive effect compared to morphine alone was observed in all tests. In the increased temperature hot plate test and in the formalin test increased antinociception was also observed when morphine was combined with chronic clomipramine treatment. In the constant temperature hot plate test no additional effect compared to morphine alone was observed when morphine and chronic clomipramine treatment were combined. These results indicate that clomipramine has an antinociceptive effect in itself, and that it may enhance the antinociceptive effects of morphine. The differences between the tests indicate that different nociceptive mechanisms are involved, and that the combination of clomipramine and morphine may be beneficial for some types of nociceptive stimuli, but not for others.

Long-lasting effects of chronic chlorimipramine treatment of rats on exploratory activity on a hole-board, and on immobility in the force swimming test

The study concerned the effects of acute and chronic clomipramine administration to male rats on exploratory activity in a novel environment (hole-board) and on immobility in the forced swimming test. Acute clomipramine administration did not alter either exploratory activity on a hole-board as measured 3 or 20 h after drug administration, or immobility in the forced swimming test as measured 20 h after drug administration. Approximately 20 h after the last injection of clomipramine, the rats chronically treated with the drug showed reduced exploratory activity on the hole-board. In contrast, chronic clomipramine treatment significantly increased the activity in the forced swimming test. The effects of the drug on exploratory and forced swimming activities persisted for 14 days after the cessation of clomipramine administration. These data indicate that chronic clomipramine administration exerted profound and long-lasting effects on central nervous system function. The long-lasting action of the drug on behaviour in the forced swimming test might explain the long-term beneficial effect of antidepressant drugs in counteractings behavioral depression.

Chronic administration of clomipramine inhibits morphine hot plate analgesia

Clomipramine, chronically administered in mice, for 3 days, inhibits partially but significantly morphine analgesia in the hot plate test, when used at dose of 10 mg/kg/day, i.p. ; 2.5 and 5 mg/kg/day were ineffective. Neither higher doses (20 and 40 mg/kg/day) nor longer duration of pretreatment (8 and 16 days) modified the intensity of this inhibition. Reduction in morphine analgesia was obtained after a 24h delay between the last injection of clomipramine and that of morphine (30 min before testing), while clomipramine did not induce any antinociceptive effect and clomipramine and desmethylclomipramine plasma and brain levels were low or undetectable. These results provide new evidence for the interaction between clomipramine and the endogenous opiate system. A pharmacokinetic interaction between clomipramin and morphine was excluded ; involvement of change in opiate and 5 HT 2 receptors by chronic administration of clomipramine is discussed.

Antidepressant drugs elevate rat pineal and plasma melatonin.

Acute administration in the mid-light phase of a number of antidepressant drugs of different pharmacological profiles elevated pineal and plasma melatonin (measured by radioimmunoassay). Following chronic treatment with the tricyclic antidepressant clomipramine, the elevation was significantly reduced. This may be an effect of reduced beta-adrenergic receptor sensitivity after chronic clomipramine administration, analogous to other findings of reduced beta-adrenergic receptor binding and reduced noradrenaline-sensitive adenylate-cyclase response.