Tricyclic antidepressant binding to lymphocyte membranes and changes during depression

Chlorimipramine and nortriptyline but not fluoxetine and fluvoxamine inhibit human polymorphonuclear cell chemotaxis in vitro

We examined the ability of antidepressant drugs belonging to different classes to interfere with human polymorphonuclear cell migration in vitro. 1. The tricyclic antidepressant drugs chlorimipramine and nortriptyline were able to block, in a dose related fashion both spontaneous and formyl-methionyl-leucyl-phenylalanine stimulated migration. This effect was already evident at very low concentrations (10(-7)M). 2. The atypical non-tricyclic antidepressant drugs fluoxetine and fluvoxamine did not affect polymorphonuclear cell mobility. 3. The ability of antidepressant drugs to interfere with polymorphonuclear cell physiology seems to depend on their chemical structures.

Changes of ligand binding after membrane phosphorylation

Phosphorylation of synaptic plasma brain membranes (SPM) causes a decrease of the specific binding of demethylated tricyclic antidepressants (TCA) and changes the affinity of 3H-imipramine and 3H-desmethylimipramine binding. The decrease of TCA binding was found also in lymphocyte membranes. In platelet membranes a decreased binding was found only with demethylated dibenzazepine derivatives. Bmax and Kd values are also decreased in the presence of phosphatidic acid or alpha-glycerolphosphate.

Effect of psychoactive drugs on lymphocyte neuropeptides

The concentrations of beta-endorphin and cholecystokinin were measured in lymphocytes obtained from young or old rats and from humans at different ages. Both in rats and humans, beta-endorphin and cholecystokinin increase with age; also in vitro, after 48-h culturing, the concentrations of beta-endorphin and cholecystokinin in lymphocytes obtained from humans of different ages changed with the same pattern observed in ex vivo experiments. In the human, beta-endorphin in lymphocytes shows a circadian rhythm that shifts approximately 6 h when compared to plasma ACTH and cortisol rhythm. The HPLC analysis of the molecular forms of beta-endorphin in lymphocytes revealed the presence of N-acetyl-beta-endorphin, with a ratio of beta-endorphin to N-acetyl-beta-endorphin ranging from 1 to 2. The concentrations of beta-endorphin and cholecystokinin were also measured in lymphocytes obtained from rats and human subjects undergoing different pharmacological treatments. In rat, the serotonin receptor antagonist metergoline decreased basal concentrations of the opioid peptide and blocked the increase of beta-endorphin concentrations induced by the serotonin precursor 5-hydroxytryptophan and the tricyclic antidepressant chlorimipramine. Also in the human, the antidepressant drug chlorimipramine increased lymphocyte beta-endorphin concentrations. In contrast to what was observed for beta-endorphin, cholecystokinin concentrations were not affected by the modulation of the serotoninergic system. Chronic treatment of rats with the dopamine receptor antagonist haloperidol induced an increase of beta-endorphin concentrations in lymphocytes that was reversed by the concomitant treatment with the dopamine receptor agonist bromocriptine, which when given alone decreased the basal concentrations of the peptide. In the human, haloperidol increased concentrations of beta-endorphin after both 24 h and chronic treatment, while cholecystokinin was never affected. Finally, beta-endorphin, but not cholecystokinin, increases both in rat and human lymphocytes after treatment with the GABA agonist sodium valproate.

Pharmacological modulation of beta-endorphin in rat peritoneal macrophages

The neuropeptide beta-endorphin is present in cells of the immune system, i.e., lymphocytes and monocytes, and its expression can be induced by immunological stimuli. In the present study, we showed that the increase of the serotoninergic availability induces an increase of beta-endorphin concentrations in rat peritoneal macrophages that is blunted by the administration of serotonin receptor antagonists. A significant increase of beta-endorphin concentrations is also evident after blocking the dopaminergic receptors, whereas a dopaminergic agonist decreases the concentrations of the peptide. Our data are consistent with a similar modulation of beta-endorphin concentrations in central nervous system and in immune cells, e.g., rat peritoneal macrophages.

Effect of immobilization stress on tricyclic antidepressant binding and serotonin uptake in rats

Immobilization stress increased the density of imipramine binding sites in platelet and cortical membranes and there was an increased serotonin uptake in platelets. There was a decrease in desipramine binding and noradrenaline uptake in lymphocytes. Our results show that stress acts on the mediator systems in various ways.