Increased glutamate transmission in the nucleus accumbens and ventral tegmental area has been proposed as a mechanism underlying sensitized behavioral responses to repeated cocaine administration. GluR1, GluR2/3, and NMDAR1 subunits of glutamate receptors were quantified from immunoblots in these brain nuclei in rats at 24 h and 3 weeks after discontinuing 1 week of daily cocaine injections. Motor behavior was monitored after the first and last injections of daily cocaine, and those rats that showed Ͼ20% increase in motor activity after the last compared with the first injection were considered to have developed behavioral sensitization. The subjects that developed behavioral sensitization showed a significant increase in GluR1 levels in the nucleus accumbens at 3 weeks but not at 24 h of withdrawal. Conversely, sensitized animals showed a significant increase in NMDAR1 and GluR1 levels in the ventral tegmental area at 1 day but not at 3 weeks of withdrawal. None of these increases occurred in the rats exposed to daily cocaine that did not develop behavioral sensitization (Ͻ20% increase in motor activity), and no changes were measured in the level of GluR2/3 in any treatment group. The functional importance of the increases in glutamate receptor subunit levels is suggested by the fact that the changes were present only in rats that developed behavioral sensitization to repeated cocaine administration.
Objective(s): Folic acid, a micronutrient supporting the natural defense system, may elevate antidepressant responses, although the lymphocyte serotonergic system has not been explored in folate-supplemented depressed patients. Methods: Twenty-seven patients were randomly assigned to groups receiving fluoxetine (20 mg) and folic acid (10 mg/day) or fluoxetine and placebo for 6 weeks. Clinical outcome was assessed according to the Hamilton Depression Rating Scale (HDRS) at the beginning, during and at the end of treatment. Blood samples were taken, plasma was separated, and lymphocytes were obtained by density gradient centrifugation with Ficoll/Hypaque and differential adhesion to plastic dishes. Fifteen healthy subjects served as controls. Plasma folate, homocysteine and vitamin B12, and serotonin concentration in lymphocytes were determined by HPLC. The HDRS score was significantly lower in patients receiving fluoxetine and folic acid compared with those receiving fluoxetine and placebo after 6 weeks of treatment (7.43 ± 1.65 vs. 11.43 ± 1.31, respectively; p = 0.04). Plasma homocysteine statistically significant decreased after folic acid (p = 0.02), but no significant changes were observed in vitamin B12. Results: Serotonin was significantly reduced after fluoxetine either with folate (p = 0.03) or placebo (p = 0.01) probably by the effect of transporter blockade. 5-Hydroxyindoleacetic acid was lower in lymphocytes of patients receiving folate (p = 0.04), indicating a reduced turnover rate, thus accumulating serotonin in the cells. A significant negative correlation was noted between homocysteine and folate. No significant correlations were present among biochemical parameters and depression severity. Conclusion: Modifications due to treatment with fluoxetine and folic acid may alter lymphocyte function in depression probably indirectly by reducing homocysteine levels and directly on lymphocytes by modifying the serotonergic system.
Serotonin transporter, measured by the specific binding of [3H]paroxetine, has been reported to be reduced in circulating lymphocytes of patients with major depression. Due to this observation, the objective of the present report was to determine the levels of serotonin transporter mRNA in lymphocytes obtained from 29 major depression patients (4 men, age 33.10 ± 1.63 years) and from 30 subjects included as a control group (4 men, age 37.54 ± 2.18 years) using RT-PCR. The patients were diagnosed according to the criteria of the American Psychiatric Association, and had a severity of depression of 32.68 ± 1.55 determined by the Hamilton Rating Scale for Depression. The DNA was submitted to polymerase chain reaction with primers for the 5′ regulatory region of human serotonin transporter, which could show the long and the short allelic forms of the transporter gene for the 5HTTLPR polymorphism. Semiquantitative analysis was performed using β-actin as internal and external standard. Control subjects presented the two allelic forms in 9.09% and depressed patients in 8.69%. The long variant was present in 73% of controls and in 60% of patients, without significant differences. There was a significant reduction in mRNA in depressed patients expressing the long allele. The number of immunofluorescent lymphocytes, labeled with a specific antibody against serotonin transporter, was reduced in the patients, as well as CD3+ lymphocytes. Serotonin and 5-hydroxyindoleacetic acid in platelet-poor plasma or lymphocytes did not differ between depressed patients and controls. The reduction in lymphocyte serotonin transporter described in major depression might be due to a decrease in the level of its mRNA and in the number of cells expressing it. These observations might implicate that functional modifications are associated with nervous-immune interactions in depression.
Objectives: Serotonin (5-HT)7 receptors in lymphocytes play a relevant role as modulators of T cell functions and might be modified by stress protocols. The aims of this work were to evaluate: (i) the presence of 5-HT7 receptors in specific lymphocyte populations, (ii) the probable modifications of them by inflammatory stress with mitogen and (iii) the effects of physical and pharmacological stress. Methods: Blood lymphocytes were isolated by density gradients and differential adhesion to plastic. Concanavalin A (Con A) was systemically administered (500 μg/kg) or added to lymphocyte cultures (2.5 μg/ml, final volume 200 μl). Physical restraint was performed in Plexiglass boxes for 5 h per day for 5 days. Reserpine administration was 2.5 mg/kg for 3 days. Immunocytochemical labeling of CD4+, CD8+ and 5-HT7 receptors, and also tryptophan hydroxylase cells was performed. mRNA of 5-HT7 receptors was evaluated by RT-PCR. Controls were included for each protocol. Results: Con A treatment or culture exposure increased the number of lymphocytes expressing 5-HT7 receptors or tryptophan hydroxylase, as compared to absence of the mitogen. Receptors were present in 12-16% of total rat lymphocytes, in ∼10% of CD4+ and in ∼5% of CD8+ cells from control rats. CD4+ decreased, and CD8+ and 5-HT7 cells increased after physical restraint. Reserpine treatment elevated CD8+ and 5-HT7 cells. Con A and physical restraint, but not reserpine treatment, significantly augmented 5-HT7 receptor mRNA in lymphocytes. Conclusions: Rat lymphocytes, expressing tryptophan hydroxylase, could synthesize 5-HT, functioning as a direct autocrine modulator. The modifications of CD4+, CD8+ and 5-HT7 receptors in lymphocytes by three stress protocols could have an impact on immune responses. In addition, the differential distribution of 5-HT7 receptors indicates potential specific physiopathological roles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.