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PubMed1987

Circadian rhythm of the Bmax of [3H]-imipramine binding in rabbit platelets.

[3H]-imipramine binding was measured in rabbit blood platelet membranes on a 24 h cycle. Animals were kept on a 14 h light (L) 10 h dark (D) schedule, and blood samples were collected at L + 2, L + 8, D + 2, D + 8 and L + 2 h on a following cycle. Significant differences were found for Bmax values of [3H]-imipramine binding, with highest values during the dark phase and lowest during the light phase. No significant differences were found in Kd values. These results suggest the existence of a circadian rhythm for the Bmax of [3H]-imipramine binding in blood platelets.

Animals↗
PubMed1988

On the 5-hydroxytryptamine transport across the plasma membrane of rabbit platelets and its inhibition by imipramine.

1. The carrier-mediated uptake of labelled 5-hydroxytryptamine (3H-5-HT) in rabbit platelets (defined as the difference between uptake observed in the absence and presence of 10 mumol l-1 imipramine) was studied after inhibition of monoamine oxidase and after a 1:13 dilution of the platelet-rich plasma (PRP) with Tris-containing buffer. 2. Irrespective of whether the rabbits were pretreated with reserpine or not, initial rates of 3H-5-HT uptake were maintained for at least 15 s. 3. Analysis of the saturation kinetics of 3H-5-HT uptake using Hill's equation yielded Km, Vmax and nH values of 130 nmol l-1, 116 pmol 10(8) platelets-1 min-1 and 1.40, respectively. Pretreatment of the animals with reserpine did not affect any of these kinetic parameters, but depleted more than 99% of the platelets' 5-HT stores. 4. The nH value remained greater than unity when the duration of incubation with 3H-5-HT was extended from 15 to 30 s and when the uptake of 3H-5-HT was inhibited by the presence of imipramine (10-40 nmol l-1). However, it was reduced to unity (with a consequential increase in Km) when 300 nmol l-1 ketanserin was present. This concentration of ketanserin did not affect 3H-5-HT uptake at substrate concentrations far below Km. 5. Imipramine inhibited 3H-5-HT uptake by increasing the Km for 3H-5-HT without changing Vmax. The Ki for this interaction was 18 nmol l-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effect of imipramine treatment on changes in heart rate and blood pressure during postural and isometric handgrip tests.

Postural and isometric handgrip tests were performed on nine patients with panic disorder and 13 patients with major depression before and after treatment with imipramine for a mean duration of 10 weeks. There were significant increases in resting supine heart rate (HR), systolic, diastolic and mean blood pressures (SBP, DBP, MBP) after treatment. There were significant increases in HR and DBP after standing from supine posture before treatment, and after treatment, there was a significant enhancement of this tachycardia. The decrease of heart rate during the change from standing to supine posture before treatment significantly decreased further after imipramine treatment. Decreases in SBP and DBP during the change from standing to supine posture were significantly smaller during the post treatment condition. Increases in SBP during the standing isometric exercise test were smaller after treatment. These findings suggest abnormal orthostatic reflexes secondary to an altered adrenergic function and/or cholinergic supersensitivity after treatment with imipramine.

Analysis of Variance↗
PubMed1986

Human cognitive function following binedaline (50 mg and 100 mg) and imipramine (75 mg): results with a new battery on tests.

The effects of two single oral doses of binedaline (50 and 100 mg), imipramine (75 mg) and placebo were compared on a range of psychological tasks (logical reasoning, the Stroop test, and five-choice serial reaction) in healthy young volunteers. The tasks, together with a mood adjective check-list, were completed prior to drug administration and 1, 2, 4 and 8 h post-dose. Binedaline had no significant effect on any of the task parameters. Imipramine impaired performance on all but the Stroop test at 2 h after drug administration. At 1, 2 and 4 h, ratings on the "deactivation" dimension of the mood adjective check-list were significantly higher following imipramine when compared to placebo. The results are discussed in terms of some general considerations about the selection and scoring of tasks to be used in the screening of drugs.

Adult↗
PubMed1976

Dffects of imipramine on auditory sensitivity in the rat in relation to initial sensitivity.

Rats were divided into 2 groups according to their absolute auditory thresholds, as measured by a psychophysical method of limits using an operant conditioning technique. The procedure required a water-deprived rat to bar press repeatedly until a 3 s pure tone (3 kHz) came on. VR-15 schedule was used to determined the frequency of occurrence of the tone. Only within 4 s after the tone onset could the rat get water reinforcement by sticking its nose into the dipper area. The descending method was used with tone intensities ranging from 120 to 40 dB, in 2 dB steps. Imipramine was then administered 3 times at 24-h intervals (40, 80 and 160 mg/kg, p.o., respectively), and each rat was tested at 4, 8, and 12 h after each administration. Rats with high initial thresholds showed a decrease in thresholds with the lower dose of imipramine, and those with low initial thresholds an increase with the higher dose. An analysis of variance of these data showed significant effects of the type of subject (in terms of the level of initial thresholds), dose and interval conditions, and their interaction. It was demonstrated that the lower the initial sensitivity the greater the increase in sensitivity by imipramine.

Animals↗
PubMed1976

A comparison of the effect of imipramine, nomifensine, and placebo on the psychomotor performance of normal males.

Imipramine (50 mg), nomifensine (50 mg) or placebo was administered early morning, late morning, and mid-afternoon to normal volunteers. The program of hourly tests included: the Digit Symbol Substitution, Perceptual Reversal, Time Estimation Test, and Simple and Complex Continuous Performances tests both of which required recognition of briefly exposed letters of the alphabet. It was found that relative to placebo or nomifensine, imipramine had a clearly detracting effect on most of the tests. Drowsiness was reported more often in the imipramine group than in the placebo and nomifensine groups combined.

Adult↗
PubMed1983

3H-imipramine binding in platelets: influence of varying proportions of intact platelets in membrane preparations on binding.

Human platelets possess high-affinity 3H-imipramine binding sites. A study in ten healthy volunteers showed that platelet preparations produced by mechanical disruption contained varying proportions of intact platelets, as measured by the cytoplasmic marker enzyme LDH. This may invalidate the protein reference. Higher proportions of membranes in the preparations lead to higher Bmax values of imipramine binding (fmol/mg protein). The use of intact platelets in imipramine binding studies is therefore preferable to membrane preparations, particularly in studies where the interindividual variation of binding parameters is of interest.

Blood Platelets↗
PubMed1978

Effects of chlordiazepoxide, amitriptyline, imipramine, and their combinations on avoidance behaviour in mice.

Chlordiazepoxide, imipramine, and amitriptyline, given alone or in combination, were tested in mice subjected to 5 daily 100-trial avoidance sessions in the shuttle-box. When the drugs were given alone, chlordiazepoxide and the lower doses of imipramine facilitated avoidance behaviour. The higher doses of the two antidepressants impaired avoidance behaviour. Mixtures of chlordiazepoxide and imipramine produced some facilitating effects, while depressant effects prevailed in the chlordiazepoxide-amitriptyline combinations.

Amitriptyline↗
PubMed1975

The interactive effects of prenatal imipramine exposure and postnatal rearing conditions on behaviour and histology.

Offspring of rats given oral doses of Saline or Imipramine (5 mg/kg) from 14-21 days prior to mating till parturition were reared, after weaning, in deprived or enriched environments. At 25-27 days and at 80-83 days the home cage behaviour of the Ss reared in the enriched environment was observed. Histological measures of brain development in both the deprived and enriched Ss were taken at the conclusion of behavioural observations. The Imipramine exposed offspring failed to show the characteristic histological changes associated with enriched rearing conditions. In addition they were behaviourally unresponsive and spent significantly less time than the Saline offspring interacting with other animals and the environment. It was argued that the physiological and behavioural unresponsiveness of the Imipramine offspring was due to a subtle teratogenic effect which prevented the Ss from interacting with the environment.

Animals↗
PubMed1982

Anticholinergic activity of imipramine and some analogs at muscarinic receptors of cultured mouse neuroblastoma cells.

Imipramine and some of its analogs (trimipramine, 3-chlorimipramine, desipramine, 3-chloro-2-hydroxyimipramine, 2-hydroxyimipramine, and didesmethylimipramine), were assayed for their potencies as antimuscarinic agents by their abilities to antagonize muscarinic receptor-mediated cyclic guanosine monophosphate (GMP) formation by cultured mouse neuroblastoma cells. Equilibrium dissociation constants for these compounds yielded the following rank order of potency at the muscarinic receptor: imipramine greater than trimipramine greater than 3-chlorimipramine greater than desipramine greater than 3-chloro-2-hydroxyimipramine greater than 2-hydroxyimipramine greater than didesmethylimipramine. These results indicate that didesmethylation of the side chain nitrogen or hydroxylation of the ring at the 2-position lead to marked reductions (30-fold and 12-fold, respectively) in antimuscarinic activity of imipramine.

Animals↗
PubMed1975

Comparison of a new antidepressive, lofepramine, with imipramine in a double-blind multicentre trial.

Lofepramine, an imipramine derivative, shows lower acute toxicity in animals when compared with desipramine and imipramine. Its anticholinergic effect is less pronounced than that of desipramine. In an open clinical trial lofepramine showed a marked antidepressive action. A double-blind multicenter trial of lofepramine v. imipramine, evaluated by means of the AMP system, showed a remarkable degree of concurrence with regards to the effects of those two products.

Adolescent↗
PubMed1984

Quantification of imipramine and its major metabolites in whole blood, brain, and other tissues of the rat by liquid chromatography.

An assay procedure is presented using high-performance liquid chromatography and fluorescence detection for simultaneous determination of imipramine, desipramine, and their 2-hydroxylated metabolites in whole blood and various tissues of the rat. By modifying methods previously described for plasma, we have developed an assay method for sensitive, reproducible quantitation of these compounds in rat plasma, whole blood, brain, liver, and fetus. Increasing the volume of the extraction solvent (20% butanol in hexane) increased recovery of imipramine and desipramine to greater than 90% for all tissues examined. No interfering peaks were observed for any of the tissues studied. Addition of n-butylamine as a modifier to the mobile phase decreased the retention of all four compounds and decreased peak tailing of the demethylated compounds. The total elution time was less than 15 min. Using these methods the coefficient of variation for all four compounds was generally less than 5% for each of the five tissues examined. The calibration curves were linear for standard concentrations of 25-2,000 ng/ml spiked tissue homogenate. This method has sufficient sensitivity and specificity for use in pharmacokinetic studies of imipramine.

Animals↗
PubMed1977

The effects of two antidepressants, imipramine and viloxazine, upon driving performance.

Forty male volunteers were randomly assigned to one of four treatment groups on a double-blind basis: (1) Imipramine--25 mg t.d.s., (2) Viloxazine--50 mg t.d.s., (3) Placebo, and (4) Control--no tablets. Tests were carried out (1) before treatment, (2) 2 h after the first dose, (3) on Day 3 after 7 doses, and (4) on Day 7 after 21 doses. The driving tasks consisted of (1) weaving around a series of bollards while simultaneously responding to an auditory logic task and (2) a gap acceptance task. Using an analysis of covariance repeated measures design, it was found that imipramine tended to increase the level of risk acceptable to the subject as compared to either placebo or control. Imipramine also impaired performance on other tasks. Viloxazine appeared to be little different from either placebo or control on any of the tasks.

Adolescent↗
PubMed1980

Specific 3H-imipramine binding in human platelets. Influence of age and sex.

Human platelets have been shown to possess high-affinity binding sites for 3H-imipramine. These binding sites have a similar affinity and drug specificity to those already described in rat brain. The platelets from healthy volunteers show no difference in 3H-imipramine binding between the sexes but there is a decrease in maximal 3H-imipramine binding with increasing age of the donor.

Adolescent↗
PubMed1987

Platelet [3H]imipramine binding in autism and schizophrenia.

[3H]Imipramine binding to platelet membranes was evaluated in ten autistics, eight schizophrenics and seven normal controls. The schizophrenics and eight out of the ten autistics were maintained on chronic neuroleptic treatment. Diagnosis of autism and schizophrenia was established according to the DSM-III criteria. No significant difference in the maximal binding capacity of [3H]imipramine (Bmax) and Kd values could be found among the three groups. It seems that the imipramine binding site is intact both in autism and schizophrenia.

Adolescent↗
PubMed1984

Binding of imipramine and cocaine to a model lipid membrane: comparison with binding to brain membranes.

[3H]Imipramine and [3H]cocaine were concentrated at membranes of liposomes prepared from phosphatidylcholine, cholesterol, and dicetylphosphate. This "binding" has an apparent dissociation constant in the micromolar range and a density close to 2 pmol/micrograms of phosphatidylcholine. The potencies of various drugs in inhibiting the binding to liposomes correlated only weakly with those in inhibiting the high-affinity binding of [3H]imipramine and [3H]cocaine to brain membranes. However, there was a highly significant correlation between the potencies of drugs in inhibiting binding to liposomes and their lipophilic character, indicating the involvement of hydrophobic bonding. Although the amounts of phosphatidylcholine and cholesterol in brain preparations in assays for high-affinity binding to brain membranes were in the same range as those used in our assays with liposomes, the inhibition of the high-affinity binding to brain membranes was only weakly dependent upon the lipophilicity of the inhibiting drug. These results indicate that lipophilicity is but one of the factors in the complex binding interactions between lipophilic substances and integral brain membranes. In addition, the results are in agreement with the suggestion that phosphatidylcholine and cholesterol are not the primary sites of high-affinity binding [3H]imipramine and [3H]cocaine to brain membranes, although it cannot be ruled out that these lipids have different properties in natural biological membranes and in artificial liposome membranes.

Animals↗
PubMed1989

The influence of repeated treatment with imipramine, (+)- and (-)-oxaprotiline on behavioural effects of dopamine D-1 and D-2 agonists.

The paper examined the action of imipramine, (+)- and (-)-oxaprotiline, administered repeatedly to rats, on the behavioural effects of the dopamine D-1 and D-2 agonists, SKF 38393 and quinpirole, respectively. The three antidepressants studied, given in the single dose or repeatedly, attenuate the enhanced grooming evoked by SKF 38393. The locomotor hyperactivity, evoked by quinpirole administered s.c., is increased by repeated but not single-dose treatment with imipramine and (+)-oxaprotiline [but not with (-)-oxaprotiline]. Quinpirole at a low dose produces the locomotor hypoactivity which is attenuated by repeated, but not single-dose, treatment with the anti-depressants studied here. Repeated imipramine and (+)-oxaprotiline [but not (-)-oxaprotiline] increase the locomotor activity effect of quinpirole injected into the nucleus accumbens. The results indicate that the enhanced responsiveness of the dopamine system, observed previously after repeated treatment with antidepressants, may be mediated by the dopamine D-2 receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1988

Effects of chronic imipramine treatment on glucocorticoid receptor immunoreactivity in various regions of the rat brain. Evidence for selective increases of glucocorticoid receptor immunoreactivity in the locus coeruleus and in 5-hydroxytryptamine nerve cell groups of the rostral ventromedial medulla.

Glucocorticoid receptor (GR) immunoreactivity (IR) was analyzed semi-automatically in the forebrain and in the lower brain stem of male rats treated for two weeks with imipramine (10 mumol/kg). Serum corticosterone and aldosterone levels were determined by means of radioimmunoassay procedures. The microdensitometric analysis demonstrated a selective increase in the GR IR in the nerve cell nuclei of the locus coeruleus (A6), of the ventral part of the reticular gigantocellular nucleus (B3L) and of the nucleus raphae magnus (B 3 M), whereas a small reduction of GR IR was found in the nucleus raphe obscurus (B2). In the morphometric analysis significant increases in the mean profile area of nuclear GR IR, which may be secondary to the increase in GR IR, were observed in the B 3 M. The serum corticosterone and aldosterone levels were not found to be significantly altered. The selective changes of GR IR may reflect the presence of an altered number of GR in these nerve cell groups and/or an altered translocation of GR to the nuclei. It is of substantial interest that these changes were observed in the presence of unchanged serum levels of corticosterone and aldosterone. It seems possible that adaptive changes in monoamine synapses induced by the chronic imipramine treatment may be responsible for the changes in GR IR found in the noradrenaline (NA) and 5-hydroxytryptamine (5-HT) cell bodies, respectively. The present results open up the possibility that chronic imipramine treatment may help to maintain the glucocorticoid receptor function in the locus coeruleus and in the 5-HT cell groups of the rostral ventromedial medulla of depressed patients.

Aldosterone↗