Smoking related diseases: the central role of monoamine oxidase

Smoking is a major risk factor of morbidity and mortality. It is well established that monoamine oxidase (MAO) activity is decreased in smokers. Serotonin (5-HT), a major substrate for MAO that circulates as a reserve pool stored in platelets, is a marker of platelet activation. We recently reported that smoking durably modifies the platelet 5-HT/MAO system by inducing a demethylation of the MAO gene promoter resulting in high MAO protein concentration persisting more than ten years after quitting smoking. The present data enlarges the results to another MAO substrate, norepinephrine (NE), further confirming the central role of MAO in tobacco use-induced diseases. Thus, MAO could be a readily accessible and helpful marker in the risk evaluation of smoking-related diseases, from cardiovascular and pulmonary diseases to depression, anxiety and cancer. The present review implements the new finding of epigenetic regulation of MAO and suggests that smoking-induced MAO demethylation can be considered as a hallmark of smoking-related cancers similarly to other aberrant DNA methylations.

[Effect of electroacupuncture on hippocampal apoptosis and JNK signal pathway in chronic stress depression rats]

OBJECTIVE

To observe the effect of electroacupuncture (EA) on hippocampal apoptosis and c-Jun N-terminal kinase (JNK) signal pathway in chronic stress depression rats so as to study its mechanism underlying acupuncture-induced improvement of depression.

METHODS

Sixty-five SD rats were randomly divided into control, control + EA, model, EA and Prozac groups, with 13 rats in each. Open-field test was used to detect the rats' behavior changes. The apoptotic rate of the hippocampal cells was detected by Annexin V fluorescein isothiocyanate (FITC)/ Propidium iodide (PI) (Annexin V-FITC/PI) double-staining, and the expression of hippocampal JNK protein detected by Western blot.

RESULTS

After repeated stress stimulation (21 days), the crossing numbers (1.8 +/- 0.2) and rearing times (0.5 +/- 0.01) in the model group were apparently lower than those (48.1 +/- 18.3, 14.2 +/- 2.4) in the control group and those (47.2 +/- 15.8, 13.5 +/- 2.6) in the control + EA group (P < 0.05). Compared with the model group, the crossing numbers and rearing times (40.2 +/- 10.1, 10.3 +/- 2.2) during 3 min in the EA group and those (39.8 +/- 12.4, 10.6 +/- 3.2) in the Prozac group were increased considerably (P < 0.05). The hippocampal apoptotic rate was significantly higher in the model group (67 +/- 10) than in the control (53 +/- 13) and control + EA groups (52 +/- 10, P < 0.05). In comparison with the model group, the apoptotic rate (29 +/- 9) of the EA group and that (51 +/- 13) of the Prozac group were significantly lower (P < 0.05). Compared with the control group, the phosphorylated JNK (p-JNK) level was considerably higher in the model group (P < 0.05); while compared with the model group, the p-JNK level was significantly lower in the EA and Pozac groups (P < 0.05). No apparent differences were found between the EA and and Prozac groups in the aforementioned indexes (P > 0.05).

CONCLUSION

EA can reduce hippocampal apoptotic rate and down-regulate hippocampal p-JNK level in depression rats, which is responsible for its effect in improving depression-induced decreased movement.

[Anxiety, depression and polymorphism of the gene encoding superoxide dismutase in patients with chronic obstructive pulmonary disease]

Chronic obstructive pulmonary disease (COPD) is a severe systemic disease leading to circulatory and respiratory failure. COPD is also a risk factor for the onset of anxiety and mood disturbances. Identification of the correlates of emotional disturbances in the course of COPD can make it possible, on the one hand, to prevent mental and behavioral disorders early in the course of this serious somatic disease, and on the other hand, to institute appropriate treatment. The aim of the study was to determine the correlation between the polymorphism of manganese superoxide dismutase signal peptide and the severity of anxiety and depression in COPD patients.

MATERIAL AND METHODS

The study group consisted of 57 patients with grade I, II and III COPD according to GOLD criteria. The control group consisted of 63 healthy nicotine addicts. In all the subjects, the genotype of position 9 of manganese superoxide dismutase signal peptide was determined, depression severity was measured with Beck Depression Scale, and anxiety as a trait and as a state was measured with Spielberg State/Trait Anxiety Inventory (STAI).

RESULTS

Among COPT patients, 16 subjects were found to have Ala/Ala genotype, 23 Val/Ala and 18 Val/Val. In the smokers' group Ala/Ala genotype was found in 29 cases, Val/Ala in 27 and Val/Val in 7. The distribution of genotype frequencies differed between the groups. In COPD patients, the mean depression severity assessed according to Beck Scale amounted to (16.52 +/- 5.63) and was higher than in smokers without COPD (13.85 +/- 4.24, p = 0.003828). The average severity of anxiety as a trait and as a state did not differ significantly in both groups. Among COPD patients, the mean severity of depressive disorders in subjects with Val/ Val genotype was 21.27 +/- 4.32 and was significantly higher than in those with Val/Ala (15.22 +/- 5.29) and Ala/Ala (12.87 +/- 3.72) genotypes. The severity of anxiety as a trait in COPD patients reached 7.72 +/- 1.21 in the subgroup with Val/Val genotype and was also higher than in those with Val/Ala genotype (6.69 +/- 1.48) and with Ala/Ala genotype (5.87 +/- 1.14). A similar correlation was observed for anxiety as a state (subjects with Val/Val genotype 6.78 +/- 1.06, with Val/Ala genotype 6.18 +/- 1.01 and with Ala/ Ala genotype 5.88 +/- 1.41). Among healthy smokers, the mean severities of depression, anxiety as a trait and anxiety as a state did not differ in subjects with different genotypes.

CONCLUSIONS

The study has demonstrated that the severity of depression is higher in COPD patients than in the group of healthy smokers. In the group of patients with COPD, Val/Val genotype at position 9 of MnSOD signal peptide is associated with more severe depression, anxiety as a trait and anxiety as a state in comparison with patients who have Val/Ala and Ala/Ala genotypes. No similar correlations were found in healthy smokers.

Indoleamine 2,3-dioxygenase activation and depressive symptoms in patients with coronary artery disease

An increase in immune-stimulated synthesis of kynurenine from tryptophan by indoleamine 2,3-dioxygenase (IDO) has been observed in patients with coronary artery disease (CAD). However, neuropsychiatric correlates of IDO activation remain unexplored. We hypothesize that IDO activation, as measured by the kynurenine to tryptophan (K/T) ratio, is associated with depressive symptoms in those with CAD. This cross-sectional study recruited subjects with CAD (n=95) from a cardiac rehabilitation facility. Demographic, anthropometric and cardiac data were obtained by chart review. Patients using an antidepressant were excluded. The presence of a major depressive episode or minor depression was assessed using a structured clinical interview for depression based on Diagnostic and Statistical Manual 4th edition criteria. The Center for Epidemiological Studies-Depression Scale (CES-D) was used to quantify depressive symptoms. A standardized exercise stress test was used to assess cardiopulmonary fitness as summarized using the peak volume of oxygen consumption (Peak VO(2)). Kynurenine and tryptophan were assayed from fasting plasma samples to obtain the K/T ratio. Higher K/T ratios were significantly associated with higher CES-D scores (beta=.322, p=.002) in a linear regression controlling for time since most recent acute coronary syndrome (tACS), age and sex. Twenty-four patients met criteria for depression (16 major depression; 8 minor depression). There was a trend towards higher K/T ratios in depressed vs. non-depressed patients (45.6+/-20.0 micromol/mmol vs. 38.5+/-15.7 micromol/mmol, F=3.778, p=.055) when controlling for age, sex and tACS. Activation of IDO is associated with the severity of depressive symptoms among patients with CAD.

Resolving the relationship between ApolipoproteinE and depression

Several studies have reported an association between the ApolipoproteinE-epsilon4 (APOE4) allele and depression among elders. However others have failed to find an association. Since APOE4 is a well recognized risk factor for Alzheimer dementia, cognitive status may represent an important confounder between APOE4 and depression. In this investigation, we examined the relationship between the ApolipoproteinE-epsilon4 allele and depression among elders accounting for cognitive status. Using a case-control design (n=1052), we investigated the association between ApolipoproteinE-epsilon4 and depression in Alzheimer disease patients (n=528) and in cognitively intact controls (n=524). We demonstrated an apparent association between the APOE4 allele and depression in the combined dataset (p=0.001) when not controlling for cognitive status. However, once stratified by the presence of Alzheimer disease, there was no association in either the Alzheimer group (p=0.290) or the cognitively intact controls (p=0.494). In this dataset there is no association between the ApolipoproteinE-epsilon4 allele and depression among those with Alzheimer disease or among cognitively intact elders. However there is a significant association between female gender and depression in the cognitively intact (p=0.003) but not among those with Alzheimer disease. Additionally, individuals with Alzheimer disease and depression had a significantly younger age of onset for their Alzheimer disease than those without depression (p=0.017).

[Influence of electroacupuncture of "Baihui" (GV 20) and "Sanyinjiao" (SP 6) on hippocampal 5-HT and AChE immuno-activity in chronic depression rats]

OBJECTIVE

To investigate the influence of electroacupuncture (EA) on 5-serotonin (5-HT) and acetyl cholinesterase (AChE) activities in hippocampus tissue in chronic stressed-induced depression rats.

METHODS

Thirty-two Wistar rats were randomized into normal control group (n=10), model group (n=11) and EA group (n=11). Chronic depression model was established by lonely raising, and chronic unpredictable mild stress for 21 days. EA (2 Hz, 1 mA) was applied to "Baihui" (GV 20) and "Sanyinjiao" (SP 6) for 20 minutes, once daily for 14 days. 5-HT and AChE expression of hippocampal CA 4 region was detected by using immunohistochemistry, and their integrated optical density (IOD) values were determined by using image analysis system.

RESULTS

Compared with normal control group, IOD values of 5-HT and AChE immuno-reaction (IR) positive neurons in hippocampal CA 4 region of model group decreased significantly (P<0.05). In comparison with model group, the IOD values of 5-HT and AChE IR positive neurons of CA 4 region in EA group increased significantly (P<0.05). No significant differences were found between EA and normal control groups in IOD values of both 5-HT and AChE IR positive neurons.

CONCLUSION

EA can upregulate 5-HT and AChE expression in hippocampal CA 4 region in depression rats, which may contribute to its effect in relieving depression.

Relationship of genetic variability and depressive symptoms to adverse events after coronary artery bypass graft surgery

OBJECTIVE

To assess genetic variability in two serotonin-related gene polymorphisms (MAOA-uVNTR and 5HTTLPR) and their relationships to depression and adverse cardiac events in a sample of patients undergoing coronary artery bypass surgery.

METHODS

A total of 427 coronary artery bypass graft (CABG) patients were genotyped for two polymorphisms and assessed for depressive symptoms at three time points, in accordance with the Center for Epidemiological Studies-Depression (CES-D): preoperative baseline; 6 months postoperative; and 1 year postoperative. Logistic regression was used to assess the association between depressive symptoms (CES-D = >16), genotype differences, and cardiac events. Because MAOA-uVNTR is sex-linked, males and females were analyzed separately for this polymorphism; sexes were combined for the 5HTTLPR analysis.

RESULTS

Depressed patients were more likely than nondepressed patients to have a new cardiac event within 2 years of surgery (p < .0001); depressed patients who carry the long (L) allele of the 5HTTLPR polymorphism were more likely than the short/short (S/S carriers to have an event (p = .0002). Genetic associations with 6-month and 1-year postoperative depressive symptoms do not survive adjustment for baseline depressive symptoms.

CONCLUSIONS

A serotonin-related gene polymorphism--5HTTLPR--was associated with adverse cardiac events post CABG, in combination with depressive symptoms. Because depressed patients with the L allele of the 5HTTLPR polymorphism were more likely to have an event compared with the S/S carriers, combining genetic and psychiatric profiling may prove useful in identifying patients at the highest risk for adverse outcomes post CABG.

[Effects of paroxetine on protein kinase PKA, PKC and CaMKII activity in different brain regions in a rat depression model]

OBJECTIVE

To evaluate the effects of paroxetine on protein kinase PKA, PKC and CaMKII activities in different brain regions in a rat model of depression.

METHODS

Thirty-six adult male SD rats were randomized into 6 groups, including one control group (I) and 5 groups of depression model established by forcing the rats to swim for 4 weeks. The 5 depression groups received no treatment (II) or were treated with paroxetine at a single dose (III), for a week (IV), 2 weeks (V) or 4 weeks (VI). The radioactivity of PKA, PKC and CaMKII in the hippocampus and prefrontal cortex was quantitatively measured using a liquid scintillation counter.

RESULTS

In the rat hippocampus, PKA and CaMKII activities were significantly lower in groups II, III, IV, and V than in groups I and VI (P<0.01 or P<0.05), but comparable between groups VI and I (P>0.05). PKC activity was significantly lower in group II than in group I (P<0.01), but showed no significant difference between the paroxetine-treated groups and group I (P>0.05). In the prefrontal cortex, the activity of PKA in groups I, II, III, and IV was similar (P>0.05), but all significantly lower than that in groups V and VI (P<0.01). PKC activity was significantly higher in groups II and III than that in group I and other paroxetine-treated groups (P<0.01), and similar between groups IV and I (P>0.05); groups V and VI had significantly lower PKC activity than group I (P<0.01). Group I had the highest CaMKII activity among the groups (P<0.01).

CONCLUSION

Chronic administration of paroxetine can reverse chronic stress-induced inhibition of PKA, PKC and CaMKII activity in rat hippocampus, while the effects of paroxetine on the protein kinases can be more complex in prefrontal cortex.

[Effects of electroacupuncture on behavior, plasma COR and expressions of PKA and PKC in hippocampus of the depression model rat]

OBJECTIVE

To probe into the mechanism of acupuncture for treatment of depression.

METHODS

Thirty-two healthy SD male rats were randomly divided into a normal group, a model group, an electroacupuncture (EA) group and a Maprotiline group. The depression rat model was made in the latter three groups, and from the second day of the experiment EA was given at Baihui (GV 20), "Yintang" (EX-HN 1), "Zusanli" (ST 36) and "Fenglong" (ST 40) in the EA group, once every other day; the rats in the Maprotiline group were treated with oral administration of Maprotiline hydrochroride, once each day. After treatment of 3 weeks, changes of behaviors, plasma cortisol (COR) level and expressions of protein kinase A (PKA) and protein kinase C (PKC) in hippocampus were observed in the rats.

RESULTS

In the depression model rats, the body weight increased slowly, and horizontal and vertical activities and consumption of sugar liquid significantly decreased; plasma cortisol content significantly increased; expressions of PKA and PKC in the hippocampus significantly reduced. In the rats of EA group, the score of behaviors, the consumption of sugar liquid and the increase of body weight were not significantly different to those in the model group, but the plasma cortisol level significantly decreased and closed to the normal level, and positive expressions of PKA and PKC in the hippocampus could be effectively reversed. In the Maprotiline group, the consumption of sugar liquid significantly increased and plasma cortisol level significantly decreased, and expressions of PKA and PKC in the hippocampus increased as compared with those in the model group.

CONCLUSION

The depression model rat has dysfunction of the hypothalamus-pituitary-adrenal axis (HPAA) and EA can regulate functions of HPAA. The mechanism is possibly carried out by regulating functions of relative enzymes in the signal transduction pathway in hippocampal cells.

Beta N-acetylglucosaminyltransferase V (Mgat5) deficiency reduces the depression-like phenotype in mice

The central nervous system (CNS) is rich in glycoconjugates, located on cell surface and in extracellular matrix. The products of Golgi UDP-GlcNAc:N-acetylglucosaminyltransferases (encoded by Mgat1, Mgat2, Mgat4 and Mgat5) act sequentially to generate the GlcNAc-branched complex-type N-glycans on glycoprotein receptors. While elimination of all the branched N-glycans in Mgat1(-/-) mouse embryos is lethal at neural tube fold stage, decreased branching is associated with late developmental defects similar to type 2 of congenital disorders of glycosylation, with developmental and psychomotor abnormalities. To study the role of complex-type N-glycans in brain function, we tested Mgat5(-/-) mice in a battery of neurological and behavioral tests. Despite the absence of tri- and tetra-antennary products, Mgat5(-/-) mice were not different from their wild-type littermates in physical and neurological assessments, anxiety level, startle reactivity and sensorimotor gating. However, they displayed a robust decrease in the immobility time in the forced swim test and the tail suspension test independent of locomotor activity, interpreted as a change in depression-like behavior. This effect was accentuated after chronic mild stress. Comparable increase in plasma corticosterone of Mgat5(+/+) and Mgat5(-/-) mice in response to acute stress shows an intact function of the hypothalamus-pituitary-adrenal axis. A change in social interactions was also observed. Our results indicate that Mgat5 modification of complex-type N-glycans on CNS glycoproteins is involved in the regulation of depression-like behavior.

[Lipid peroxidation and copper-zinc superoxide dismutase activity in patients treated with fluoxetine during the first episode of depression]

In recent years researchers have made a lot of studies to determine the molecular and neurochemical mechanisms which are the basis of depressive disorders. Apoptosis is a cause of the limbic system neuronal cells defect in patients suffering from depression. The antioxidant system is the best known molecular mechanism which protects the cells from apoptosis. This system exists inside and outside of the cells compartments. There is much evidence that antioxidant enzymes keep neuronal cells safe from apoptosis, which is a result of oxidative stress. It also limits the premature ageing of cells.

AIM

We tried to give an answer to three questions. 1. Is the activity of cooper-zinc superoxide dismutase (CuZnSOD) and lipid peroxydation level (TBARS) different in patients and the healthy control group? 2. Does the activity of CuZnSOD change due to fluoxetine treatment? 3. What is the difference of TBARS concentration in platelets isolated from patients before and after treatment?

METHOD

The study comprised of 32 patients diagnosed with depression. The activity of CuZnSOD in platelets was measured by Misra and Fridovich's method. The thrombocyte concentration of TBARS was measured by Placer and coop. method.

RESULTS AND CONCLUSIONS

1. The activity of CuZnSOD in platelets of depressive patients is lower than in the healthy control group, but the differences are not significant. 2. The activity of CuZnSOD rises after fluoxetine treatment. 3. The concentration of TBARS is higher in patients than in the healthy control group. 4. The intensity of lipid peroxydation is statistically lower after fluoxetine treatment.

[The influence of clomipramine on CYP2D6 activity]

AIM

Genetically determined activity ofCYP2D6 may be modified by some drugs through inhibition processes. Inhibition properties of TCA's were confirmed mainly in in vitro studies. The aim of the study was to assess the influence of clomipramine on CYP2D6 activity in vivo.

METHOD

11 patients diagnosed with depression according to ICD-10 and DSM-IV (major depression) criteria were included in the study. In all the cases clomipramine therapy was indicated. CYP2D6 activity was assessed by the phenotyping method. All patients were treated simultaneously. Each of the patients ingested one tablet containing 100 mg of sparteine sulfate. Urine excreted during the following 6 h was collected. Based on sparteine metabolic ratio (MR) the phenotype status was estimated twice: after the wash-out period, before clomipramine treatment, sparteine metabolic ratio (MRI), and after 2-weeks of clomipramine treatment (MR2).

RESULTS

During clomipramine treatment MR2 values were statistically significantly higher than MRI. In 3 patients (27.3%) treated with clomipramine the changes of phenotype status were observed.

CONCLUSIONS

Clomipramine is a CYP2D6 inhibitor and may change the CYP2D6 phenotype status (EM into PM).

Role of glycogen synthase kinase-3beta in early depressive behavior induced by mild traumatic brain injury

Traumatic brain injury (TBI) is a triggering event for a set of pathophysiological changes and concomitant depressive behavior. Glycogen synthase kinase-3 (GSK-3) is a potent in vivo regulator of cell apoptosis and, in addition, is implicated in depressive behavior. In this study, we investigated the role of GSK-3 in the physiological model of mild TBI (mTBI) at both the cellular and behavior levels. mTBI resulted in increased phosphorylation of inhibitory site serine(9) of GSK-3beta, which coincided with increased serine(473) phosphorylation of its upstream kinase PKB and accumulation of its downstream target beta-catenin in the hippocampus. mTBI induced a depressive behavior which was evident as early as 24 h post-injury. Pretreatment with GSK-3 inhibitors, lithium, or L803-mts prevented mTBI-induced depression. We suggest that mTBI elicits a pro-survival cascade of PKB/GSK-3beta/beta-catenin as part of a rehabilitation program. Furthermore, the use of selective GSK-3 inhibitors may have therapeutic benefits in treatment conditions associated with brain injury.

The depressive-like behaviors are correlated with decreased phosphorylation of mitogen-activated protein kinases in rat brain following chronic forced swim stress

In the present study, 40 Sprague-Dawley rats were divided into forced swim stress group and controls, with 20 rats in each group (10 for behavioral tests, 10 for protein detection). The forced swim stress group received swim stress for 14 consecutive days, and the controls were stress-free. After stress, 20 rats were tested for behavioral observation using body weight gain, open field, elevated plus-maze and saccharin preference test, and 20 rats were decapitated for protein detection. The extracellular signal-regulated kinase (Erk) and phospho-Erk (P-Erk) in the hippocampus and prefrontal cortex were determined using western blot. It was found that the body weight gain of stressed animals during the 7 stressed days and the 14 stressed days was significantly decreased compared to that of controls. Stressed animals spent less time in open arms and longer time in closed arms. The stressed animals demonstrated decreased locomotor activity and increased grooming in open field. The saccharin solution intake and the ratio of saccharin solution intake to total liquid intake were both decreased in the stressed group. Stressed animals showed decreased P-Erk2 and decreased ratio of P-Erk2 to total Erk2 in the hippocampus and prefrontal cortex, but their Erk1/2 was increased in the prefrontal cortex with no change in hippocampus. The saccharin solution intake positively correlated with the P-Erk2 in the hippocampus and negatively correlated with the Erk2 in the prefrontal cortex. In conclusion, chronic forced swim stress was a good animal model of depression, and it induced depressive-like behavior and decreased P-Erk2 in the hippocampus and prefrontal cortex in rats. The depressive-like behaviors were correlated with decreased phosphorylation of Erk, which suggested that the dysfunction of Erk activity might be one of biological mechanisms underlying depression induced by stress.

Behavioral characterization of CD26 deficient mice in animal tests of anxiety and antidepressant-like activity

CD26 exhibits a dipeptidylpeptidase-IV function (DPPIV) which regulates neuropeptide activity by N-terminal processing. Because abnormal plasma DPPIV was associated in mammals with behavioral changes, we examined the behavior of CD26-/- mice resulting from targeted inactivation of the gene. These animals had a decreased immobility in the forced swim and tail suspension tests, indicating a reduced depression-like behavior. We addressed some factors that could affect these results. No major differences between mutants and controls were observed in the black/white box test that investigates anxiety. In the hole-board apparatus that explores both curiosity and anxiety, CD26-/- mice of both genders made significantly more head dips than controls. In a motor activity test, mutants displayed higher horizontal and vertical activities i.e. increased novelty-induced behavioral activation. We conclude that DPPIV inactivation in mice broadly leads to an antidepressant-like and hyperactive phenotype.

[The relationship between the Wnt signaling and the psychiatric diseases]

It has been demonstrated that the neuronal plasticity and resilience could participate in the pathophysiology of neurodegenerative diseases such as Alzheimer and others like depression and schizophrenia. Recently, it has been proposed a new intracellular pathway, known as Wnt pathway, which could be related to the induction of the plastic changes mentioned above. The glycogen synthase kinase-3beta (GSK-3beta), one of the main enzymes of the Wnt signaling, has been associated to Alzheimer;s and schizophrenia diseases etiology. Furthermore, the mood stabilizing agents;s action mechanism, like lithium and valproic acid, implies the inhibition of this protein. The issue of this work is to describe the proteins that are recruited when this pathway is activated and the GSK-3beta role in the pathologies mentioned.

Keynote review: phosphodiesterase-4 as a therapeutic target

Cyclic AMP (cAMP) is a key second messenger in all cells. It is compartmentalized within cells and its levels are controlled, as a result of spatially discrete signaling cassettes controlling its generation, detection and degradation. Underpinning compartmentalized cAMP signaling are approximately 20 members of the phosphodiesterase-4 (PDE4) family. The selective inhibition of this family generates profound, functional effects and PDE4 inhibitors are currently under development to provide potential, novel therapeutics for the treatment of inflammatory diseases, such as asthma, chronic obstructive pulmonary disease and psoriasis, as well as treating depression and serving as cognitive enhancers. Here, we delineate the range of PDE4 isoforms, their role in signaling, their structural biology and related preclinical and clinical pharmacology.

Genotype-dependent activity of tryptophan hydroxylase-2 determines the response to citalopram in a mouse model of depression

Polymorphism of tryptophan hydroxylase, the rate-limiting enzyme in the synthesis of brain serotonin (5-HT), is associated with less synthesis of brain 5-HT in DBA/2J and BALB/c than in C57BL/6J and 129/Sv mice. We selected the forced swimming test, a mouse model used to assess the antidepressant potential of drugs, and neurochemical techniques to study strain differences in the response to citalopram, a selective 5-HT reuptake inhibitor. Citalopram reduced immobility time in C57BL/6J and 129/Sv mice but had no such effect in DBA/2J and BALB/c mice. The drug reduced accumulation of 5-hydroxytryptophan (5-HTP), an indicator of 5-HT synthesis, in C57BL/6J and 129/Sv mice but much less in DBA/2J and BALB/c mice. Pretreatment with tryptophan raised 5-HTP accumulation and reinstated the antidepressant-like effect of citalopram in DBA/2J and BALB/c mice, whereas pharmacological inhibition of 5-HT synthesis prevented the effect of citalopram in C57BL/6J and 129/Sv mice. Because there were no strain differences in catecholamine synthesis, locomotor activity, and brain levels of citalopram at the end of the behavioral test, the results suggest that the failure of citalopram to reduce immobility time in DBA/2J and BALB/c mice is attributable to genotype-dependent impairment of 5-HT synthesis. Interstrain comparisons could probably be a useful strategy for understanding the mechanisms underlying the response to selective serotonin reuptake inhibitors.

Na+,K(+)-ATPase activity is reduced in hippocampus of rats submitted to an experimental model of depression: effect of chronic lithium treatment and possible involvement in learning deficits

This study was undertaken to verify the effects of chronic stress and lithium treatments on the hippocampal Na+,K(+)-ATPase activity of rats, as well as to investigate the effects of stress interruption and post-stress lithium treatment on this enzyme activity and on spatial memory. Two experiments were carried out; in the first experiment, adult male Wistar rats were divided into two groups: control and submitted to a chronic variate stress paradigm, and subdivided into treated or not with LiCl. After 40 days of treatment, rats were killed, and Na+,K(+)-ATPase activity was determined. In the second experiment, rats were stressed during 40 days, and their performance was evaluated in the Water Maze task. The stressed group was then subdivided into four groups, with continued or interrupted stress treatment and treated or not with lithium for 30 additional days. After a second evaluation of performance in the Water Maze, rats were killed and Na+,K(+)-ATPase activity was also measured. Results showed an impairment in Na+,K(+)-ATPase activity and in Water Maze performance of chronically stressed rats, which were prevented by lithium treatment and reversed by lithium treatment and by stress interruption. These results suggest that the modulation of Na+,K(+)-ATPase activity may be one of the mechanisms of action of lithium in the treatment of mood disorders.

Effects of potassium channel inhibitors in the forced swimming test: Possible involvement of l-arginine-nitric oxide-soluble guanylate cyclase pathway

The effects of inhibitors of different subtypes of potassium (K+) channels were investigated in the mouse forced swimming test (FST). The treatment of animals with tetraethylammonium (TEA, a non-specific inhibitor of potassium channels, 0.25-2.5 ng/site, intracerebroventricular, i.c.v.), glibenclamide (an ATP-sensitive potassium channels (K(ATP) inhibitor, 0.05-5 ng/site, i.c.v.), apamine (a small conductance calcium-activated potassium channels inhibitor (SKCa), 0.1-1 ng/site, i.c.v.), charybdotoxin (a large- (big, BK) and intermediate- (IK) conductance calcium-activated potassium channels inhibitor, 2.5-25 ng/site, i.c.v.) produced an anti-depressant-like effect in the FST. At the highest effective doses, none of the drugs affected the locomotor activity in an open-field. Besides that, the pre-treatment of animals with l-arginine (a nitric oxide (NO) precursor, 750 mg/kg, intraperitoneal, i.p.) or sildenafil (a specific phosphodiesterase type 5 (PDE5) inhibitor, 5 mg/kg, i.p.) prevented the anti-depressant-like effect of all K+ channel inhibitors. The present results demonstrate that the decrease in the immobility time in the FST elicited by the inhibition of several subtypes of K+ channels is also dependent on the inhibition of NO-cGMP synthesis.

Hypothalamic nitric oxide synthase in affective disorder: focus on the suprachiasmatic nucleus

Depression is frequently associated with dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, which leads to repeated episodes of hypercortisolemia. Hypothalamic paraventricular neurons are believed to trigger these processes by aberrant generation and/or release of corticotropin releasing hormone, oxytocin, vasopressin, and nitric oxide (NO). Recent findings from two independent laboratories have demonstrated that the suprachiasmatic nucleus, which in part controls the cellular activity of paraventricular neurons (PVN), is also involved in affective disorder. The aim of the present study was to elucidate by stereological analysis, whether suprachiasmatic nucleus (SCN) nitric oxide synthase and neurophysin generating neurons are affected in neuropsychiatric disorders. We show that compared to controls the number of nitric oxide synthase immunoreactive neurons is greatly reduced both in depression and in schizophrenia. In subjects with affective disorder there was a correlation between the number of NOS-expressing cells and duration of treatment with antidepressants. The number of neurophysin-expressing SCN neurons was also fewer in cases with mood disorder. It is concluded that SCN-derived NO may be a relevant pathophysiological factor in neuropsychiatric disorders.