Depression as a spreading adjustment disorder of monoaminergic neurons: a case for primary implication of the locus coeruleus

Role of depression in heart failure--choosing the right antidepressive treatment

Major depression is a common feature of heart failure patients and possibly stems from their common biochemical background. Depression and heart failure co-morbidity has several clinical implications on the prognosis of these patients. Furthermore antidepressive drugs have known cardiovascular side effects, while their safety and efficacy in heart failure has not been fully elucidated yet. The right choice of antidepressive treatment in heart failure constitutes an issue of high importance as it can affect the clinical outcome of these patients. In this article we highlight the role of major depression in heart failure and demonstrate their common biochemical background. Moreover we review the acquired so far knowledge on the use of the various categories of antidepressants in heart failure by reference to the existing clinical studies on antidepressants efficacy and safety in heart failure. Even though certain conclusions cannot be drawn yet, evidence suggests that the use of selective serotonin reuptake inhibitors may have a beneficial effect on clinical outcome of heart failure patients.

Effect of alpha2A-adrenoceptor C-1291G genotype and maltreatment on hyperactivity and inattention in adolescents

The C-1291G polymorphism (rs1800544) in the promoter region of the alpha(2A)-adrenoceptor gene (ADRA2A) has been associated with attention deficit and hyperactivity in clinical samples. We have examined the effect of ADRA2A C-1291G on inattentive, hyperactive and aggressive behaviour in a population representative cohort of healthy schoolchildren, and possible interaction of genotype with family relations. Ratings on aggressiveness, motor restlessness and concentration difficulties were obtained from the class teachers by using the Hyperactivity Scale of af Klinteberg, and the teacher-report version of SNAP-IV. The relations in the family were reported by children. Symptom scores, self-reports and genotype data of 429 15-years old children (196 boys, 233 girls) were available for analysis. There was a significant interaction effect of maltreatment and the ADRA2A genotype on behavioural functioning in 15years old boys. Boys with CC genotype and higher score of maltreatment demonstrated more overactive behaviour and concentration difficulties than boys with CC genotype and low maltreatment score. They also had more inattentive symptoms measured by SNAP-IV. Among boys with low maltreatment score, subjects with CC genotype demonstrated less overactivity than G allele carriers. In girls, the G allele carriers did not differ from the CC genotype, but in maltreated girls with GG genotype aggression and inattention symptoms were reduced, and the score of aggressive behaviour was also lower compared to maltreated girls with CC genotype. Our data suggest that family environmental factors may act together with the alpha(2A)-adrenoceptor genotype to increase the expression of hyperactive and inattentive symptoms in adolescents.

Investigating the role of protein kinase-G in the antidepressant-like response of sildenafil in combination with muscarinic acetylcholine receptor antagonism

The cGMP/PK-G pathway plays a crucial role in neuroprotection and neurotrophin support, and is possibly involved in antidepressant action. Recently we reported on a novel antidepressant-like response following simultaneous administration of sildenafil (phosphodiesterase 5 (PDE5) inhibitor, thereby increasing cGMP levels), and atropine (muscarinic acetylcholine receptor antagonist) in the rat forced swim test (FST). However, it is unclear whether the antidepressant-like activity of sildenafil+atropine is mediated via the activation of PK-G, an important down-stream effector for cGMP, and whether this may target known pathways in antidepressant action. We investigated whether the antidepressant-like response of sildenafil+/-atropine could be reversed by Rp-8-Br-PET-cGMP, a PK-G inhibitor, and also whether a combination of 8-Br-cGMP (PK-G activator)+/-atropine would likewise be active in the FST, and whether this combination could be attenuated by a PK-G inhibitor. 8-Br-cGMP alone, but not sildenafil alone, reduced immobility and selectively increased swimming in the FST. The antidepressant-like action of sildenafil was only evident following co-administration of atropine, and selectively increased climbing behaviour. Importantly, PK-G inhibition prevented the antidepressant-like effects of both 8-Br-cGMP and the sildenafil/atropine combination. These results confirm cholinergic-cGMP-PK-G interactions in the antidepressant-like effects of sildenafil, putatively acting via noradrenergic mechanisms, whereas direct PK-G activation induces antidepressant-like effects that are associated with enhancement of serotonergic neurotransmission.

Galanin, galanin receptor subtypes and depression-like behaviour

The pathophysiology of depression remains unclear, but involves disturbances in brain monoaminergic transmission. Current antidepressant drugs, which act by enhancing this type of neurotransmission, have limited therapeutic efficacy in a number of patients, and also cause serious side-effects, which limits their compliance. Increasing evidence suggests that neuropeptides, including galanin, can be of relevance in mood disorders. Galanin is co-expressed with and modulates noradrenaline and serotonin transmission, both implicated in depression. Pharmacological and genetic studies suggest a role for galanin in depression-like behaviour in rodents, involving specific receptor subtypes. Thus, stimulation of GalR1 and/or GalR3 receptors results in depression-like phenotype, while activation of the GalR2 receptor reduces depression-like behaviour in the rat. These findings suggest that galanin receptor subtypes may represent novel targets for the development of antidepressant drugs.

Inter-individual differences in neurobiology as vulnerability factors for affective disorders: implications for psychopharmacology

Susceptibility to affective disorders is individually different, and determined both by genetic variance and life events that cause significant differences in the CNS structure and function between individual subjects. Therefore it is plausible that search for the inter-individual differences in endophenotypes that mediate the effects of causal factors, both genetic and environmental, will reveal the substrates for vulnerability, help to clarify pathogenetic mechanisms, and possibly aid in developing strategies to discover better, more personalized treatments. This review first examines comparatively a number of animal models of human affect and affect-related disorders that rely on persistent inter-individual differences, and then highlights some of the neurobiological findings in these models that are compatible with much of research in human behavioural and personality traits. Many behaviours occur in specific combinations in several models, but often remarkable dissociations are observed, providing a variety of constellations of traits. It is concluded that more systematic comparative experimentation on behaviour and neurobiology in different models is warranted to reveal possible "building blocks" of affect-related personality common in animals and humans. Looking into the perspectives in psychopharmacology the focus is placed on probable associations of inter-individual differences with brain structure and function, personality and coping strategies, and psychiatric vulnerability, highlighting some unexpected interactions between vulnerability endophenotypes, adverse life events, and behavioural traits. It is argued that further studies on inter-individual differences in affect and underlying neurobiology should include formal modeling of their epistatic, hierarchical and dynamic nature.

Effect of imipramine on nerve excitability in GC rats

Imipramine test (7.5 mg/kg) revealed a persistent positive reaction of Wistar rats, which manifested in reduced excitability of animals. Oral administration of imipramine solution was followed by unstable behavioral reactions in GC rats. Norepinephrine concentration in the cortical and limbic regions of these animals remained unchanged, while plasma corticosterone concentration decreased to the control level and did not differ from that in Wistar rats. Our results indicate that imipramine has a modulatory effect on destabilization of the adaptive system in catatonic GC rats.

Glucocorticoid status affects antidepressant regulation of locus coeruleus tyrosine hydroxylase and dorsal raphé tryptophan hydroxylase gene expression

Brainstem monoaminergic nuclei express glucocorticoid receptors (GR), and glucocorticoids have been shown to inhibit expression of enzymes involved in monoamine synthesis. Monoamine deficits have been implicated in depression pathology. However, it is unknown if antidepressants regulate brainstem GR, and if glucocorticoids might influence antidepressant effects on monoamine-synthesizing enzymes. Our lab has found opposing effects of the monoamine oxidase inhibitor phenelzine and the tricyclic antidepressant imipramine on HPA activity and forebrain GR gene expression. We therefore hypothesized that phenelzine and imipramine would also affect brainstem GR gene expression differentially, and that antidepressant-induced changes in GR expression would correlate with effects on monoamine-synthesizing enzyme expression. Using in situ hybridization, we measured effects of chronic antidepressant treatment on brainstem GR, locus coeruleus and ventral tegmental area (VTA) tyrosine hydroxylase (TH), and dorsal raphé tryptophan hydroxylase (TPH2) gene expression in male C57BL/6 mice that were adrenalectomized and replaced with defined levels of corticosterone. GR expression was decreased by phenelzine in the locus coeruleus and decreased by imipramine in the dorsal raphé. Phenelzine increased locus coeruleus TH and imipramine increased dorsal raphé TPH2 gene expression in a glucocorticoid-dependent manner, suggesting that increases in these enzymes were due to relief of inhibitory glucocorticoid signaling. We did not find antidepressant effects on GR or TH expression in the VTA or on mineralocorticoid receptor (MR) expression in any of the nuclei examined. Our findings represent a potential mechanism through which antidepressants and glucocorticoids could alter both HPA activity and mood via effects on brainstem GR, norepinephrine, and serotonin.

Serotonin: modulator of a drive to withdraw

Serotonin is a fundamental neuromodulator in both vertebrate and invertebrate nervous systems, with a suspected role in many human mental disorders. Yet, because of the complexity of serotonergic function, researchers have been unable to agree on a general theory. One function suggested for serotonin systems is the avoidance of threat. We propose and review evidence for an alternative hypothesis, that a phylogenetically primitive of function of serotonin is to oppose the activating neuromodulators (particularly noradrenalin and dopamine). The functional effect of this opposition can be seen as applying a drive to withdraw from dangerous, aversive or high stimulation environments. Proposing that serotonin is involved in a drive to withdraw and seek contentment, instead of a drive to avoid, may be compatible with several lines of evidence on serotonin function and may facilitate a better understanding of serotonergic neuromodulation in human psychopathology.

Differential stress-induced neuronal activation patterns in mouse lines selectively bred for high, normal or low anxiety

There is evidence for a disturbed perception and processing of emotional information in pathological anxiety. Using a rat model of trait anxiety generated by selective breeding, we previously revealed differences in challenge-induced neuronal activation in fear/anxiety-related brain areas between high (HAB) and low (LAB) anxiety rats. To confirm whether findings generalize to other species, we used the corresponding HAB/LAB mouse model and investigated c-Fos responses to elevated open arm exposure. Moreover, for the first time we included normal anxiety mice (NAB) for comparison. The results confirm that HAB mice show hyperanxious behavior compared to their LAB counterparts, with NAB mice displaying an intermediate anxiety phenotype. Open arm challenge revealed altered c-Fos response in prefrontal-cortical, limbic and hypothalamic areas in HAB mice as compared to LAB mice, and this was similar to the differences observed previously in the HAB/LAB rat lines. In mice, however, additional differential c-Fos response was observed in subregions of the amygdala, hypothalamus, nucleus accumbens, midbrain and pons. Most of these differences were also seen between HAB and NAB mice, indicating that it is predominately the HAB line showing altered neuronal processing. Hypothalamic hypoactivation detected in LAB versus NAB mice may be associated with their low-anxiety/high-novelty-seeking phenotype. The detection of similarly disturbed activation patterns in a key set of anxiety-related brain areas in two independent models reflecting psychopathological states of trait anxiety confirms the notion that the altered brain activation in HAB animals is indeed characteristic of enhanced (pathological) anxiety, providing information for potential targets of therapeutic intervention.

Effects of the G(-656)A variant on CREB1 promoter activity in a neuronal cell line: interactions with gonadal steroids and stress

Major depressive disorder (MDD) constitutes a major public health problem worldwide and affects women twice as frequently as men. Previous genetic studies have revealed significant evidence of linkage of the cAMP-responsive element-binding protein 1 (CREB1) gene region (2q33-35) to mood disorders among women from families with recurrent, early-onset MDD (RE-MDD), a severe and familial subtype of MDD. A rare G-to-A transition at position -656 in the CREB1 promoter co-segregates with mood disorders in women from these families, implicating CREB1 as a sex-related susceptibility gene for unipolar mood disorders. In the current study, the functional significance of the CREB1 promoter variant was determined using transfection experiments that employed plasmid constructs containing the wild-type or variant CREB1 promoters coupled to a reporter gene. The results support the hypothesis that the A(-656) allele contributes to the development of MDD in women through selective alteration of CREB1 promoter activity by female gonadal steroids in noradrenergic neuronal cells. Furthermore, exaggeration of these effects during a simulated stress condition may be relevant to reported gene-environment interactions that contribute to the emergence of MDD in clinical populations.

Psychiatric profile and attention deficits in postural tachycardia syndrome

OBJECTIVES

Patients with postural tachycardia syndrome (POTS) often appear anxious and report inattention. Patients with POTS were formally assessed for psychiatric disorders and inattention and compared with patients with attention deficit hyperactivity disorder (ADHD) and control subjects.

METHODS

Patients with POTS (n = 21), ADHD (n = 18) and normal control subjects (n = 20) were assessed for DSM-IV psychiatric disorders and completed a battery of questionnaires that assessed depression, anxiety and ADHD characteristics.

RESULTS

Patients with POTS did not have an increased prevalence of major depression or anxiety disorders, including panic disorder, compared with the general population. Patients with POTS had mild depression. They scored as moderately anxious on the Beck Anxiety Inventory but did not exhibit a high level of anxiety sensitivity. Patients with POTS scored significantly higher on inattention and ADHD subscales than control subjects. These symptoms were not present during childhood.

CONCLUSIONS

Patients with POTS do not have an increased lifetime prevalence of psychiatric disorders. Although they may seem anxious, they do not have excess cognitive anxiety. They do experience significant inattention which may be an important source of disability.

Modulation of adenylyl cyclase activity in rat striatal homogenate by dopaminergic receptors

We have characterized the modulation of adenylyl cyclase (AC) activity by ligands of dopaminergic receptors in rat striatal homogenate and compared the results with receptor-ligand binding affinities. Despite the fact that rat striatum contains high level of both dopamine D(1) and D(2) receptors, only the D(1)-specific AC activation by agonists could be determined. All D(1)-receptor agonists (dopamine, dihydrexidine, and A 77636) used were able to increase cAMP accumulation in a concentration-dependent manner, while D(1)-receptor antagonists (SCH23390, SKF83566, and butaclamol) blocked the effects induced by the aforementioned agonists. At the same time, the D(2)-receptor agonist quinpirole and antagonist sulpiride had no effect on cAMP accumulation in striatal homogenate neither on the basal level nor on the activated level of AC, while inhibited [(3)H]raclopride binding to these membranes. Comparing the ligands of the D(1) receptor in modulating the activity of AC and displacing D(1)-receptor-specific radioligand [(3)H]SCH23390 binding revealed that the ligands modulate both of these processes with similar affinities. It indicates that under given experimental conditions, only dopamine D(1)-receptor-mediated stimulation of AC activity can be measured in membrane homogenate of rat striatum, while dopamine D(2)-receptor effects remain fully hidden.

Oestrogen receptor beta contributes to the transient sex difference in tyrosine hydroxylase expression in the mouse locus coeruleus

Oestrogen receptors (ERs) are important for sexual differentiation of the brain. Previous studies in rats have reported that the locus coeruleus (LC), a catecholaminergic nucleus in the brain stem, is sexually dimorphic such that females have more neurones than males. We hypothesised that ERs may be important for sexual differentiation of this nucleus in mice. Because previous studies reported conflicting results regarding ER protein expression in the mouse LC, we evaluated ER alpha and ER beta gene expression by in situ hybridisation and the real-time reverse transcription-polymerase chain reaction. We demonstrated that both ER alpha and ER beta mRNAs are present in tyrosine hydroxylase-immunoreactive (TH-ir) cells in the male LC. In the female LC, ER alpha mRNA is present at levels similar to males, whereas ER beta mRNA expression is significantly lower than in males. Similar to rats, male mice have fewer TH-ir cells in the LC than females at 60 days after birth, but the difference is absent at 120 days after birth when females exhibit a similar reduction in TH-ir cells. The transient sex difference is ER beta-dependent because is it absent in ER beta knockout mice, and is due to regulation of TH expression and not from death of TH-ir cells. Testicular hormones produced at adolescence are necessary for the regulation of TH expression in the male LC because orchidectomy of pre-pubertal males prevented the decrease in TH-ir cells, whereas treatment of gonadectomized males with testosterone or its metabolite, 5 alpha-androstan-3beta,17beta-diol, restored the intact male phenotype. Overall, these studies indicate that ER beta is important in regulating TH expression in the mouse LC.

Functional interactions between dopamine, serotonin and norepinephrine neurons: an in-vivo electrophysiological study in rats with monoaminergic lesions

Anatomical studies have established the existence of reciprocal relationships between the main population of monoamine, serotonin (5-HT), norepinephrine (NE) and dopamine (DA) neurons in the brain. The present study was thus conducted to examine the firing activity of 5-HT and NE neurons in DA-depleted rats, as well as the firing activity of DA neurons in 5-HT- or NE-depleted rats. The selective lesion of DA neurons elicited by 6-hydroxydopamine (6-OHDA) decreased the spontaneous firing activity of dorsal raphe (DR) nucleus 5-HT neurons by 60%, thus revealing the excitatory effect of the DA input on these 5-HT neurons. In contrast, the selective lesion of 5-HT neurons produced by 5,7-dihydroxytryptamine (5,7-DHT) enhanced by 36% the firing activity of VTA DA neurons, thereby indicating an inhibitory effect of the 5-HT input on these DA neurons. With regard to the reciprocal interaction between DA and NE neurons, it was observed that the selective loss of DA neurons achieved by the intra-ventral tegmental area (VTA) injection of 6-OHDA increased the firing activity of a subset of locus coeruleus (LC) NE neurons by 47%. The selective loss of NE neurons in response to the intra-LC injection of 6-OHDA enhanced the firing activity of VTA DA neurons by 70%, demonstrating a net inhibitory role of the NE input on VTA DA neurons. These findings have important consequences for antidepressant treatments aimed at enhancing simultaneously 5-HT, NE and DA transmission. Indeed, based on the understanding of such interactions, it may be possible to develop strategies to improve the effectiveness of antidepressant drugs by preventing counter-productive negative feedback actions.

Associations between an alpha 2A adrenergic receptor gene polymorphism and adolescent personality

The aim of this study was to investigate the impact of the C-1291G polymorphism in the promoter region of the alpha 2A adrenoreceptor gene (ADRA2A) to the personality traits. In the present study, data of the younger cohort of the Estonian Children Personality Behaviour and Health Study was used (N = 419). Personality traits were assessed by 240-item (Estonian Personality Item Pool NEO (EPIP-NEO)). Restriction enzyme MspI was used after PCR amplification to genotype the subjects according to C-1291G polymorphism of the ADRA2A. There were no significant differences on the level of the Big Five personality domains between genotypes; however, there were three significant differences on the level of different subscales. The subjects with GG genotype had significantly higher scores on Depression and significantly lower scores on Morality and Orderliness compared to subjects with CC and CG genotypes. There was a significant interaction between sex and ADRA2A polymorphism regarding E1, Friendliness; E2, Gregariousness; and E6, Cheerfulness. With CC and CG genotypes girls had higher scores on extraversion scales than boys, but with GG genotype boys score higher than girls with GG genotype. It is concluded that the gene polymorphism in the ADRA2A has an influence on personality traits in adolescents.

Light deprivation damages monoamine neurons and produces a depressive behavioral phenotype in rats

Light is an important environmental factor for regulation of mood. There is a high frequency of seasonal affective disorder in high latitudes where light exposure is limited, and bright light therapy is a successful antidepressant treatment. We recently showed that rats kept for 6 weeks in constant darkness (DD) have anatomical and behavioral features similar to depressed patients, including dysregulation of circadian sleep-waking rhythms and impairment of the noradrenergic (NA)-locus coeruleus (LC) system. Here, we analyzed the cell viability of neural systems related to the pathophysiology of depression after DD, including NA-LC, serotoninergic-raphe nuclei and dopaminergic-ventral tegmental area neurons, and evaluated the depressive behavioral profile of light-deprived rats. We found increased apoptosis in the three aminergic systems analyzed when compared with animals maintained for 6 weeks in 12:12 light-dark conditions. The most apoptosis was observed in NA-LC neurons, associated with a significant decrease in the number of cortical NA boutons. Behaviorally, DD induced a depression-like condition as measured by increased immobility in a forced swim test (FST). DD did not appear to be stressful (no effect on adrenal or body weights) but may have sensitized responses to subsequent stressors (increased fecal number during the FST). We also found that the antidepressant desipramine decreases these neural and behavioral effects of light deprivation. These findings indicate that DD induces neural damage in monoamine brain systems and this damage is associated with a depressive behavioral phenotype. Our results suggest a mechanism whereby prolonged limited light intensity could negatively impact mood.

Rats with high or low sociability are differently affected by chronic variable stress

Depression is strongly related to social behavior. We have previously shown that social behavior of rats is individually stable. The purpose of the present study was to compare the sensitivity of animals with different sociability to chronic variable stress (CVS). Four social interaction tests were performed with 60 single-housed male Sprague-Dawley rats. Twenty rats with the lowest and 20 with the highest average social activity time were selected as low sociability (LS) and high sociability (HS) rats, respectively. Both groups were further divided into control and stress groups with equal average body weight. The CVS procedure lasted for 3 weeks. The stressors applied were cold water and wet bedding, imitation of injection, stroboscopic light, movement restriction in a small cage, tail pinch with a clothespin, and strong illumination during the predicted dark phase. In HS-rats, but not in LS-rats, CVS reduced sucrose intake compared with baseline after 3 weeks, suggesting that HS-rats are more vulnerable to anhedonia elicited by CVS. LS-animals were more anxious in the social interaction and open field tests, but stress eliminated differences with HS-animals in the social interaction test and increased their activity in the forced swimming test. In LS-rats stress increased ex vivo dopamine levels and reduced 5-HT levels in the frontal cortex, suggesting that the increased behavioral activity after stress may be related to increased impulsivity. This study thus revealed that animals with high sociability trait are more vulnerable to anhedonia elicited by chronic stress in conditions of single housing.

Changes in regional long-term oxidative metabolism induced by partial serotonergic denervation and chronic variable stress in rat brain

Stressful experiences and genetic predisposition have both independent and interactive contributions to the development of depression. The serotonergic system is involved in the development of depression, and administration of neurotoxins that specifically compromise its function leads to symptoms of affective disorders. In order to find out which brain regions are most affected by stress, partial serotonergic denervation and their combination, chronic variable stress (CVS) was applied for 3 week. Serotonergic denervation was elicited by parachloroampetamine (PCA, 2mg/kg), and cytochrome oxidase histochemistry was used to characterize the long-term levels of neuronal oxidative energy metabolism. PCA pretreatment blocked the increase in oxidative activity in chronically stressed rats in medial preoptic area, cortical and medial amygdala. PCA raised oxidative activity compared to control animals in substantia nigra and ventrolateral division of laterodorsal thalamus. CVS reduced the oxidative activity induced by PCA in suprachiasmatic hypothalamus, anteroventral thalamus, hippocampal CA3 region and cortical amygdala. In the dorsal part of the anterior olfactory nucleus chronic stress blocked the decrease in oxidative activity evoked by PCA. Conclusively, partial serotonergic denervation with PCA and chronic variable stress both had independent effects on long-term energy metabolism in several rat brain structures, tending to increase it. However, partial serotonergic denervation by parachloroampetamine and chronic variable stress had in many brain regions an interactive effect on energy metabolism, each factor reducing the effect of the other, which could reflect the weakening of adaptive mechanisms.

Rat behavior after chronic variable stress and partial lesioning of 5-HT-ergic neurotransmission: effects of citalopram

Deficits in serotonergic (5-HT-ergic) neurotransmission and stressful life events have been implicated in affective disorders, and chronic variable stress (CVS) can elicit behavioral changes reminiscent of increased emotionality, anxiety and atypical depression after partial 5-HT depletion. This study examined the effect of chronic citalopram treatment (10 mg/kg daily) on these changes. Parachloroamphetamine (PCA) (2 mg/kg) reduced the levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the frontal cortex, increased anxiety in the social interaction test, and increased activity in the open field. CVS reduced social activity in the social interaction test and immobility time in the forced swimming test. Reduction of excrements left during immobilization indicated partial adaptation with the CVS. Specific stressors had different effects on body weight gain, shorter lasting stressors having a smaller effect in general than those that lasted longer. Combination of CVS and PCA increased sucrose intake after two weeks of stress. In addition, combination of the two treatments reduced diving in the forced swimming test. Citalopram prevented the increase in sucrose consumption in the PCA+CVS rats, and in 5-HT-depleted animals blocked the increase in struggling and reduced the number of defecations in the forced swim test. In conclusion, citalopram treatment prevented several effects of either 5-HT depletion or combined PCA+CVS treatment, suggesting that these behavioral changes could be used in studies on the neural mechanisms underlying emotional behavior that may have relevance to the neurobiology of depression.

Effects of rapid eye movement sleep deprivation on hypocretin neurons in the hypothalamus of a rat model of depression

Hypocretin (Hcrt, also known as orexin) is a hypothalamic neuropeptide linked to narcolepsy, a disorder diagnosed by the appearance of rapid eye-movement sleep (REMS)-state characteristics during waking. Major targets of Hcrt-containing fibers include the locus coeruleus and the raphe nucleus, areas with important roles in regulation of mood and sleep. A relationship between REMS and mood is suggested by studies demonstrating that REMS-deprivation (REMSD) ameliorates depressive symptoms in humans. Additional support is found in animal studies where antidepressants and REMSD have similar effects on monoamiergic systems thought to be involved in major depression. Recently, we have reported that Wistar-Kyoto (WKY) rats, an animal model of depression, have reduced number and size of hypothalamic cells expressing Hcrt-immunoractivity compared to the parent, Wistar (WIS) strain, suggesting the possibility that the depressive-like attributes of the WKY rat may be determined by this relative reduction in Hcrt cells [Allard, J.S., Tizabi, Y., Shaffery, J.P., Trouth, C.O., Manaye, K., 2004. Stereological analysis of the hypothalamic hypocretin/orexin neurons in an animal model of depression. Neuropeptides 38, 311-315]. In this study, we sought to test the hypothesis that REMSD would result in a greater increase in the number and/or size of hypothalamic, Hcrt-immunoreactive (Hcrt-ir) neurons in WKY, compared to WIS rats. The effect of REMSD, using the multiple-small-platforms-over-water (SPRD) method, on size and number of Hcrt-ir cells were compared within and across strains of rats that experienced multiple-large-platforms-over-water (LPC) as well as to those in a normal, home-cage-control (CC) setting. In accord with previous findings, the number of Hcrt-ir cells was larger in all three WIS groups compared to the respective WKY groups. REMSD produced a 20% increase (p<0.02) in the number of hypothalamic Hcrt-ir neurons in WKY rats compared to cage control WKY (WKY-CC) animals. However, an unexpected higher increase in number of Hcrt-ir cells was also observed in the WKY-LPC group compared to both WKY-CC (31%, p<0.001) and WKY-SPRD (20%, p<0.002) rats. A similar, smaller, but non-significant, pattern of change was noted in WIS-LPC group. Overall the data indicate a differential response to environmental manipulations where WKY rats appear to be more reactive than WIS rats. Moreover, the findings do not support direct antidepressant-like activity for REMSD on hypothalamic Hcrt neurons in WKY rats.

Liquid chromatography method for detecting native fluorescent bioamines in urine using post-column derivatization and intramolecular FRET detection

Liquid chromatography (LC) with fluorescence detection is described for simultaneous determination of native fluorescent bioamines (indoleamines and catecholamines). This is based on intramolecular fluorescence resonance energy transfer (FRET) in an LC system following post-column derivatization of native fluorescent bioamines' amino groups with o-phthalaldehyde (OPA). OPA fluorescence was achieved through an intramolecular FRET process when the molecules were excited at maximum excitation wavelength of the native fluorescent bioamines. Bioamines separated by reversed-phase LC on ODS column were derivatized with OPA and 2-mercaptoethanol. This method provides sufficient selectivity and sensitivity for the determination of normetanephrine, dopamine, tyrosine, 5-hydroxytryptamine, tryptamine, and tryptophan in healthy human urine without prior sample purification.

Stress-induced release of substance P in the locus coeruleus modulates cortical noradrenaline release

Several lines of evidence implicate the neuropeptide substance P (SP) in the modulation of emotional behavior. Interaction between SP and noradrenergic systems has been proposed to be important in the regulation of stress, depression, and anxiety mechanisms; however, most evidence so far is based on studies in unchallenged and/or anesthetized animals. Thus, by using a dual-probe microdialysis approach in freely moving animals, the aim of the present study was to investigate whether a relevant stressor can trigger the release of SP in the locus coeruleus (LC) and whether and how this response modulates noradrenaline (NA) transmission both in the LC and in the medial prefrontal cortex (mPFC), an important LC terminal region involved in emotional processing. While confirming previous reports that neurokinin 1 receptor (NK1R) antagonists activate cortical noradrenergic transmission under resting conditions, we present evidence that this interaction is opposite during stress challenge. Our results show that exposure to forced swimming considerably enhanced the release of SP and NA in the LC. Administration of a selective NK1R antagonist into the LC potentiated this NA response within the LC but abolished the stress-induced increase in NA release within the mPFC. These findings demonstrate stress-induced increase in endogenous extracellular SP levels within the LC exerting a facilitatory effect on the noradrenergic pathway to the mPFC. The attenuation of stress-induced hyperactivation of this pathway by NK1R antagonists, presumably via enhancing NA and autoinhibition in the LC, may contribute to the therapeutic efficacy of these drugs known to ameliorate symptoms of stress-related disorders.

Altered brain activation pattern associated with drug-induced attenuation of enhanced depression-like behavior in rats bred for high anxiety

BACKGROUND

The enhanced depression-like behavior in the forced swim test displayed by rats selectively bred for high anxiety-related behavior (HAB) as compared with their low anxiety counterparts (LAB) is abolished by chronic paroxetine treatment. The aim of the present study was to identify neuronal substrates underlying this treatment response in HABs.

METHODS

The HAB rats received paroxetine (10 mg/kg/day) for 24 days via drinking water, and drug-induced modulation of neuronal activation patterns in response to forced swimming was mapped with the expression of the immediate early gene c-Fos as marker.

RESULTS

Chronic paroxetine treatment reduced the immobility scores during forced swimming, confirming the previously observed antidepressant-like effect in these animals, and attenuated the forced swim-induced c-Fos response in a restricted set (11 of 70) of brain areas. These included limbic areas such as the prelimbic cortex, parts of the amygdala, the bed nucleus of the stria terminalis, dorsal hippocampus, dorsal lateral septum as well as hypothalamic and hindbrain areas (dorsolateral periaqueductal gray [PAG], locus coeruleus). Untreated LAB rats, which displayed low depression-like behavior comparable to that of treated HABs, also showed low swim stress-induced c-Fos response in most of these same areas, further supporting an association of attenuated neuronal excitability in the identified areas with attenuated depression-like behavior.

CONCLUSIONS

These findings indicate that modulation of neuronal activation in a restricted set of defined, mainly limbic as well as selected hypothalamic and hindbrain areas by paroxetine treatment is associated with the reduction of enhanced depression-like behavior in a psychopathological animal model.

Determination of Catecholamines and Indoleamines in Human Urine Based on Intramolecular Excimer-forming Derivatization and Fluorescence Detection

A liquid chromatographic (LC) determination of catecholamines and indoleamines is described. This is based on intramolecular excimer-forming fluorescence derivatization with 4-(1-pyrene)butanoyl chloride, followed by reversed-phase LC. The analytes, containing an amino moiety and phenolic hydroxyl moieties in a molecule, were converted to the corresponding polypyrene-labeled derivatives by one-step derivatization. They afforded intramolecular excimer fluorescence, which can clearly be discriminated from the normal fluorescence emitted from reagent blanks. The detection limits (S/N = 3) for catecholamines and indoleamines were femto-mole levels per 20-microL injection. Furthermore, this method was applied to a urine assay.

Association between plasma inflammatory markers and irrational beliefs; the ATTICA epidemiological study

OBJECTIVE

Recent research data suggest that inflammation and/or depression are associated with the development and progression of cardiovascular disease (CVD). Considering that depression may arise as a response to irrational beliefs according to the Ellis model of psychological disturbances and therapy, we sought to evaluate whether irrational beliefs are associated with plasma inflammatory factors in cardiovascular disease-free people.

METHOD

From May 2001 to December 2002 we randomly enrolled 453 men (23-69 years old) and 400 women (24-71 years old) stratified by age and gender. C-reactive protein, interleukin-6, serum amyloid-A, tumor necrosis factor-alpha and white blood cells were measured in all participants. Detailed dietary characteristics of these people were assessed through a validated food frequency questionnaire. Subjects completed also the irrational beliefs inventory (IBI), which is a brief self-report measure consistent with the Ellis model of psychological disturbance and therapy and the Zung's Depression questionnaire.

RESULTS

The IBI scores were similar in men and women (53+/-11 vs. 53+/-10, p = 0.83). IBI score was positively correlated with C-reactive protein (rho = 0.14, p = 0. 02), interleukin-6 (rho = 0.11, p = 0.02), tumor necrosis factor-alpha (rho = 0.21, p = 0.014) and white blood cell counts (rho = 0.14, p = 0.02). These associations were confirmed even after adjusting for age, sex, years of school, body mass index, physical activity status, depression level and food items consumed by the participants.

CONCLUSION

These findings indicate that irrational beliefs are associated with increased inflammation process, among apparently healthy individuals.

Galanin receptor antagonists : a potential novel pharmacological treatment for mood disorders

The pathophysiology of mood disorders involves several genetic and social predisposing factors, as well as a dysregulated response to chronic stress. Accumulated evidence during the last two decades has implicated disturbances in brain serotonin and/or noradrenaline (norepinephrine) neurotransmission in the aetiology of depression. In fact, current pharmacological treatment for mood disorders is based on the use of drugs that act mainly by enhancing brain serotonin and noradrenaline neurotransmission by blockade of the active reuptake mechanism for these neurotransmitters. However, current antidepressant drugs have a delayed onset of therapeutic action, and a substantial number of patients do not respond adequately to them. In addition, these drugs have a number of adverse effects that limit patient compliance. In view of this, there is an intense search to identify novel (receptor) targets for antidepressant therapy. Recent studies have indicated that several neuropeptides and their receptors are potential candidates for the development of novel antidepressant treatment. In this context, galanin is of particular interest, since it is co-localised with serotonin in the dorsal raphe nucleus and with noradrenaline in the locus coeruleus, nuclei known to play a major role in affective disorders and in the action of antidepressant drugs. The actions of galanin are mediated by three receptor subtypes (GAL1, GAL2 and GAL3), which are coupled to different intracellular effector systems. Studies in rats have shown that galanin administered intracerebroventricularly is a potent inhibitor of mesencephalic serotonergic neurotransmission, as indicated by a long-lasting reduction in the release of serotonin in the hippocampus. This inhibitory effect is related to activation of the galanin receptors located on the dorsal raphe neurons. Moreover, intracerebroventricular galanin alters the gene expression of serotonin 5-HT1A autoreceptors in the dorsal raphe and also changes their functional activity. In addition, galanin produces a functional blockade of postsynaptic 5-HT1A receptor-mediated responses. Both pharmacological and genetic studies suggest a role for galanin in depression-like behaviour in rodent models. Transgenic mice overexpressing galanin under the control of the platelet-derived growth factor-beta promoter display increased immobility in the forced swim test. Intracerebroventricular administration of galanin in the rat increases depression-like behaviour, and this is fully blocked by the nonselective peptide galanin receptor antagonist M35. Importantly, M35 alone administered intracerebroventricularly produces an antidepressant-like effect. Recently, newly developed receptor-specific nonpeptidergic galanin GAL3 receptor antagonists (SNAP-37889 and SNAP-398299), which cross the blood-brain barrier after systemic administration, have shown antidepressant-like activity in several animal models. On the other hand, stimulation of the GAL2 receptor at the raphe level by local application of the GAL2 receptor agonist galanin (2-11) has been shown to increase serotonin levels in the hippocampus and dorsal raphe. These results indicate an important (mainly inhibitory) role of galanin as a regulator of brain serotonin and 5-HT1A receptor-mediated transmission, which may be of potential importance for understanding mood disorders and for the development of antidepressant drugs. Taken together, the present evidence suggests that antidepressant efficacy may be associated with compounds acting as antagonists at the GAL3 and/or possibly GAL1 receptors, and/or agonists at the GAL2 receptor.

Neurosteroids, neuroactive steroids, and symptoms of affective disorders

Neurosteroids (NS) are steroids synthesized by the brain. Neuroactive steroids (NAS) refers to steroids that, independent of their origin, are capable of modifying neural activities. NAS bind and modulate different types of membrane receptors. The gamma amino butyric acid (GABA) and sigma receptor complexes have been the most extensively studied. Oxidized ring A reduced pregnanes, tetrahydroprogesterone (THP), and tetrahydrodeoxycorticosterone (THDOC) bind to the progesterone intracellular receptor (PR), and in this way can also regulate gene expression. Animal experimentation showed that salient symptoms of depression, viz., anxiety, sleep disturbances, and memory and sexual dysfunctions, are modulated by NAS. In turn, psychotropic drugs modulate NS and NAS levels. NS levels as well as NAS plasma concentrations change in patients with depression syndromes, the levels return to normal baseline with recovery, but normalization is not necessary for successful therapy. Results from current studies on the evolution of nervous systems, including evolutionary developmental biology as well as anatomical and physiological findings, almost preclude a categorical classification of the psychiatric ailments the human brain succumbs to. The persistence in maintaining such essentialist classifications may help to explain why up to now the search for biological markers in psychiatry has been an unrewarding effort. It is proposed that it would be more fruitful to focus on relationships between NAS and symptoms of psychiatric disorders, rather than with typologically defined disorders.

CCK and NPY as anti-anxiety treatment targets: promises, pitfalls, and strategies

Short CCK peptides elicit panic attacks in humans and anxiogenic-like effects in some animal models, but CCK receptor antagonists have not been found clinically effective. Yet CCK overactivity appears to be involved in submissive behaviour, and CCKB receptor expression and binding are increased in suicide victims and animal models of anxiety. Preliminary data suggest that involvement of CCK and its receptor subtypes in anxiety can be better described when focusing on distinct endophenotypes, and considering environmental contingencies and confounds originating from interactions with dopamin-, opioid- and glutamatergic neurotransmission. In contrast, NPY is an anti-anxiety peptide with robust effects in various animal models when administrated into several brain regions. Studies with non-peptide antagonists selective for receptor subtypes have revealed the role of endogenous NPY in active coping. At least Y1, Y2 and Y5 receptors in various brain regions are involved, with the strongest evidence for contribution of Y1.

In vivo effect of tramadol on locus coeruleus neurons is mediated by alpha2-adrenoceptors and modulated by serotonin

Tramadol is a centrally-acting analgesic endowed with opioid, noradrenergic and serotonergic properties. Various data suggest that, in addition to its analgesic effect, tramadol may have antidepressant and anxiolytic-like effects. This study investigates, through single-unit extracellular recording techniques, the in vivo effects of tramadol on locus coeruleus (LC) neurons and its possible effects on alpha(2)-adrenoceptors, opioid receptors and the 5-HT system. Tramadol produced a dose-dependent and complete inhibition of LC activity (ED(50)=2.1mg/kg). This inhibitory effect was prevented and reversed by the selective alpha(2)-adrenoceptor antagonist, idazoxan, but not by the opioid receptor antagonist, naloxone. The inhibition of the synthesis of 5-HT by p-chlorophenylalanine and the pre-administration of the 5-HT(1A) receptor agonist, 8-OH-DPAT at 40microg/kg, caused a significant potentiation of the tramadol effect decreasing the ED(50) by 53% and 67% respectively. Lower doses of 8-OH-DPAT, of 1 and 4microg/kg, did not significantly modify the tramadol effect. In summary, the results indicate that tramadol elicits an inhibitory effect on LC neurons in vivo through alpha(2)-adrenoceptors. Moreover, this effect is modulated by the 5-HT system and particularly by 5-HT(1A) receptors.

Airjet and FG-7142-induced Fos expression differs in rats selectively bred for high and low anxiety-related behavior

We reported recently that two rat lines bred for either high (HAB) or low (LAB) anxiety-related behavior display differential Fos expression in restricted parts of the fear/anxiety circuitry when exposed to mild anxiety evoked in exploratory anxiety tests. Since different forms of anxiety are thought to activate different parts of the anxiety circuitry, we investigated now whether (1) an aversive stimulus which elicits escape behavior (airjet) and (2) the anxiogenic/panicogenic drug FG-7142 would reveal further differences in Fos expression as a marker of neuronal activation between HAB and LAB rats. Both airjet exposure and FG-7142 induced Fos expression in both lines in various anxiety-related brain areas. HAB rats, which displayed exaggerated escape responses during airjet exposure, exhibited increased Fos expression in brain areas including the hypothalamus, periaqueductal gray and locus coeruleus, as well as blunted Fos activation in the cingulate cortex in response to airjet and/or FG-7142. The results corroborate previous findings showing that trait anxiety affects neuronal excitability in hypothalamic and medial prefrontal areas. Furthermore, by using airjet as well as FG-7142, we now reveal that enhanced trait anxiety is also associated with neuronal hyperexcitability in the locus coeruleus and the periaqueductal gray, suggesting that investigation of an array of different anxiogenic stimuli is important for the detection of altered neuronal processing in trait anxiety.

5-HT receptor subtypes involved in the anxiogenic-like action and associated Fos response of acute fluoxetine treatment in rats

RATIONALE

We have recently reported that acute treatment with the selective serotonin reuptake inhibitor fluoxetine exacerbates escape responses to airjet and facilitates airjet-induced activation of locus coeruleus (LC) neurons.

OBJECTIVE

Here we aimed to identify the 5-HT receptor subtype(s) mediating the anxiogenic-like effects of acute fluoxetine in this paradigm and to study whether chronic fluoxetine treatment would alter these responses.

METHODS

The expression of the immediate early gene c-fos was used as a marker of neuronal activation.

RESULTS

Acute fluoxetine increased the airjet-induced escape behaviour and Fos expression in the LC of saline-pretreated rats. Pretreatment with the 5-HT(2C/2B) antagonist SB 206553, but not with the 5-HT1A antagonist WAY 100635, the 5-HT1B antagonist SB 224289 or the 5-HT3 antagonist Y-25130 inhibited the fluoxetine-induced increase in escape behaviour and the associated elevated LC Fos response. The selective 5-HT2C agonist MK-212 mimicked the anxiogenic response of fluoxetine. Chronic treatment with fluoxetine abolished the anxiogenic-like effect and led to a normalization of the enhanced fluoxetine-induced Fos response to airjet.

CONCLUSIONS

Taken together, the results indicate that the anxiogenic-like effect as well as the facilitated neuronal reactivity induced by acute fluoxetine in the airjet model is mediated primarily by activation of 5-HT2C receptors.

Compensatory changes in the noradrenergic nervous system in the locus ceruleus and hippocampus of postmortem subjects with Alzheimer's disease and dementia with Lewy bodies

In Alzheimer's disease (AD), there is a significant loss of locus ceruleus (LC) noradrenergic neurons. However, functional and anatomical evidence indicates that the remaining noradrenergic neurons may be compensating for the loss. Because the noradrenergic system plays an important role in learning and memory, it is important to determine whether compensation occurs in noradrenergic neurons in the LC and hippocampus of subjects with AD or a related dementing disorder, dementia with Lewy bodies (DLB). We observed profound neuronal loss in the LC in AD and DLB subjects with three major changes in the noradrenergic system consistent with compensation: (1) an increase in tyrosine hydroxylase (TH) mRNA expression in the remaining neurons; (2) sprouting of dendrites into peri-LC dendritic zone, as determined by alpha2-adrenoreceptors (ARs) and norepinephrine transporter binding sites; and (3) sprouting of axonal projections to the hippocampus as determined by alpha2-ARs. In AD and DLB subjects, the postsynaptic alpha1-ARs were normal to elevated. Expression of alpha1A- and alpha2A-AR mRNA in the hippocampus of AD and DLB subjects were not altered, but expression of alpha1D- and alpha2C-AR mRNA was significantly reduced in the hippocampus of AD and DLB subjects. Therefore, in AD and DLB subjects, there is compensation occurring in the remaining noradrenergic neurons, but there does appear to be a loss of specific AR in the hippocampus. Because changes in these noradrenergic markers in AD versus DLB subjects were similar (except neuronal loss and the increase in TH mRNA were somewhat greater in DLB subjects), the presence of Lewy bodies in addition to plaques and tangles in DLB subjects does not appear to further affect the noradrenergic compensatory changes.

Dexmedetomidine-Induced Decreases in Accumbal Dopamine in the Rat Are Partly Mediated via the Locus Coeruleus

We have demonstrated previously that the systemic administration of the selective alpha2-adrenoceptor agonist dexmedetomidine (Dex) decreases extracellular dopamine (DA) levels in the rat nucleus accumbens (NAcc). Because the locus ceruleus (LC) is a noradrenergic center linked to several of the pharmacological effects of Dex, we investigated the role of the LC in Dex-induced modulation of accumbal DA. Microdialysis probes were implanted in the NAcc and LC of Sprague-Dawley rats, and Dex 5 mM (Dex-High, n = 6), Dex 0.5 mM (Dex-Mid, n = 5), Dex 5 microM (Dex-Low, n = 6), or artificial cerebrospinal fluid (control, n = 5) was administered in the LC via retrograde microdialysis for 45 min. Extracellular DA levels were continuously measured in the NAcc dialysates using high-performance liquid chromatography coupled to electrochemical detection. Dex produced significant decreases in extracellular DA in the NAcc. Accumbal DA decreased maximally to 68.9% +/- 8.8%, 75.1% +/- 6.5%, and 77.04% +/- 12.8% of baseline in the Dex-High, Dex-Mid, and Dex-Low groups, respectively. No significant decrease in extracellular DA was observed in the control group. The coadministration of the highly selective alpha2-adrenoceptor antagonist (n = 6) RS 79948 20 mM prevented the Dex-induced decrease in accumbal DA. These data suggest that the LC plays a role in Dex-induced modulation of mesolimbic DA and support the hypothesis that noradrenergic systems can regulate remote dopaminergic sites in the central nervous system.

Catecholamines mediate stress-induced increases in peripheral and central inflammatory cytokines

Proinflammatory cytokines act at receptors in the CNS to alter physiological and behavioral responses. Exposure to stressors increases both peripheral and central proinflammatory cytokines, yet the mechanism(s) of induction remain unknown. Experiments here examined the role of catecholamines in the in vivo induction of proinflammatory cytokines following tailshock stress. Rats were pretreated i.p. with 2.0 mg/kg prazosin (alpha1-adrenoceptor antagonist), 10.0 mg/kg propranolol (beta-adrenoceptor antagonist), or 5.0 mg/kg labetalol (alpha1- and beta-adrenoceptor antagonist) 30 min prior to tailshock exposure and plasma interleukin-1beta (IL-1beta) and IL-6, along with tissue interleukin-1beta from the hypothalamus, hippocampus, and pituitary were measured immediately following stressor termination. Prazosin attenuated stress-induced plasma IL-1beta and IL-6, but had no effect on tissue IL-1beta levels, while propranolol attenuated plasma IL-6 and blocked tissue IL-1beta elevation, and labetalol, which cannot cross the blood-brain barrier, attenuated plasma IL-1beta and IL-6, blocked pituitary IL-1beta, but had no effect on central tissue IL-1beta levels. Furthermore, administration of 50.0 mg/kg N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride, a neurotoxin that lesions neural projections from the locus coeruleus, prevented stress-induced elevation in hippocampal IL-1beta, a region highly innervated by the locus coeruleus, but had no effect on hypothalamic IL-1beta, a region that receives few locus coeruleus projections. Finally, i.p. injection of 5.0 mg/kg isoproterenol (beta-adrenoceptor agonist) was sufficient to induce circulating IL-1 and IL-6, and tissue IL-1beta. These data suggest catecholamines play an important role in the induction of stress-induced proinflammatory cytokines and that beta-adrenoceptors are critical for tissue IL-1beta induction, while both alpha- and beta-adrenoceptors contribute to the induction of plasma cytokines.

Genetic reduction of noradrenergic function alters social memory and reduces aggression in mice

Aberrant social behavior is a hallmark of many cognitive, mood, and neurological disorders, although the specific molecular mechanisms underlying the behavioral deficits are not well understood. The neurotransmitter noradrenaline (NA) has been implicated in some of these disorders, as well as in several aspects of social behavior in humans and animals. We tested dopamine beta-hydroxylase knockout (Dbh -/-) mice that lack NA in various social behavior paradigms. Dbh -/- mice have relatively normal performance in the elevated plus maze, light/dark box, and open field test - three measures of anxiety - and a social recognition test. In contrast, Dbh -/- mice displayed a specific deficit in a social discrimination task and had a nearly complete absence of resident-intruder aggression. These results indicate that intact NA signaling is required for some types of social memory and aggression, but that a lack of NA does not greatly affect anxiety in mice. Further exploration of NA deficits in neurological disease may reveal mechanisms of aberrant social behavior.

α2-Adrenoceptor involvement in the in vitro inhibitory effect of citalopram on a subpopulation of rat locus coeruleus neurons

The aim of the present study was to investigate the modulation of locus coeruleus neurons by the selective serotonin (5-HT) reuptake inhibitor citalopram using single-unit extracellular recordings in rat brain slices. Citalopram inhibited the activity of a subpopulation of locus coeruleus neurons; thus 10 microM citalopram inhibited neurons by 53+/-17% (5 out of 15 cells), whereas the inhibition due to 100 microM was 64+/-4% (32 out of 42 cells). This effect was partially reversed (47+/-11%) by the alpha(2)-adrenoceptor antagonist idazoxan (10 microM), whereas it was unaffected by antagonists for 5-HT(1A), 5-HT(2,) and 5-HT(3) receptors, and mu opioid receptors. 5-HT (50 or 200 microM), the 5-HT(1A) receptor agonist 8-OH-DPAT (+/-)-8-hydroxy-2-(DI-n-propyl-amino) tetralin hydrobromide, 10 microM) and the 5-HT(2) receptor agonist DOI ([+/-]-2,5-dimetoxy-4-iodoamphetamine) hydrochloride, 10 or 30 microM) also inhibited a subpopulation of locus coeruleus cells. In addition, citalopram but not 5-HT, enhanced by 1.7 fold the inhibitory effect of noradrenaline. Long-term treatment with citalopram (20 mg/kg/day) did not modify the effect of noradrenaline and bromoxidine. Taken together, our results indicate that citalopram exerts an inhibitory effect on locus coeruleus noradrenergic neurons. alpha(2)-adrenoceptor activation may underlie this effect as a result of elevated levels of noradrenaline in the synaptic cleft.

Phasic activation of monkey locus ceruleus neurons by simple decisions in a forced-choice task

The noradrenergic locus ceruleus (LC) system has been implicated in several behavioral functions, most notably, response to salient sensory events. Here, we provide new evidence indicating a role in the execution of responses associated with simple decisions. We examined impulse activity of monkey LC neurons during performance of a forced-choice discrimination task. The timing of LC activity more closely tracked behavioral responses than stimulus presentation. LC neurons were phasically activated preceding behavioral responses for both correct and incorrect identifications but were not activated by stimuli that failed to elicit lever responses nor by nontask-related lever movements. We hypothesize that the LC responds to the outcome of task-related decision processes, facilitating their influence on overt behavior. This role of the LC in regulating the behavioral outcome of decisional processes contrasts with more traditional views of LC responses as primarily related to sensory processes.

Behavioral and neurochemical studies on brain aging in galanin overexpressing mice

To study possible involvement of galanin in brain aging quality, we have investigated behavioral, neurochemical and morphological parameters in aged mice overexpressing galanin under the platelet-derived growth factor B promoter (GalOE mice) compared to wild-type littermates (WT mice). The behavioral analysis in the forced swim test showed that old GalOE animals spent more time in immobility compared to WT. In the activity cage test, galanin overexpression counteracted the age-induced decrease in exploratory behavior. The neurochemical analysis showed a 30% decrease in noradrenaline overflow in the cerebral cortex of WT old mice that was not present in age-matched GalOE mice. Our results indicate that overexpression of galanin can influence several behavioral and neurochemical parameters in old mice.

Steroids, neuroactive steroids and neurosteroids in psychopathology

The term "neurosteroid" (NS) was introduced by Baulieu in 1981 to name a steroid hormone, dehydroepiandrosterone sulfate (DHEAS), that was found at high levels in the brain long after gonadectomy and adrenalectomy, and shown later to be synthetized by the brain. Later, androstenedione, pregnenolone and their sulfates and lipid derivatives as well as tetrahydrometabolites of progesterone (P) and deoxycorticosterone (DOC) were identified as neurosteroids. The term "neuroactive steroid" (NAS) refers to steroids which, independent of their origin, are capable of modifying neural activities. NASs bind and modulate different types of membrane receptors. The GABA and sigma receptor complexes have been the most extensively studied, while glycine-activated chloride channels, nicotinic acetylcholine receptors, voltage-activated calcium channels, although less explored, are also modulated by NASs. Within the glutamate receptor family, N-methyl-d-aspartate (NMDA) receptors, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and kainate receptors have also been demonstrated to be a target for steroid modulation. Besides their membrane effects, once inside the neuron oxidation of Ring A reduced pregnanes, THP and THDOC, bind to the progesterone intracellular receptor and regulate gene expression through this path. The involvement of NASs on depression syndromes, anxiety disorders, stress responses to different stress stimuli, memory processes and related phenomena such as long-term potentiation are reviewed and critically evaluated. The importance of context for the interpretation of behavioral effects of hormones as well as for hormonal levels in body fluids is emphasized. Some suggestions for further research are given.

Behavioural characterisation of young adult transgenic mice overexpressing galanin under the PDGF-B promoter

The behavioural phenotype of transgenic mice (3- to 5-months old) overexpressing galanin (GalOE) under the platelet-derived growth factor B (PDGF-B) promoter was evaluated in a battery of tests, including open field, locomotor cages, light-dark exploration test, elevated plus-maze and the Porsolt forced swim test. Learning and memory were assessed in the passive avoidance and the Morris water maze tasks. No difference between genotypes was found in exploratory activity in the open field. GalOE mice showed a slight increase in spontaneous locomotor activity assessed in the locomotor cages, but the amphetamine-induced increase in locomotor activity was somewhat lower in GalOE mice. Anxiety-like behaviour in the three different tests including open field, light-dark exploration and elevated plus-maze did not differ between genotypes. In the Porsolt forced swim test, GalOE mice displayed an increased time of immobility, indicative of increased learned helplessness possibly reflecting increased stress-susceptibility and/or depression-like behaviour. GalOE mice showed normal learning and memory retention in the passive avoidance and the Morris water maze tasks. These data support the hypothesis that galanin may have a role in functions related to mood states including affective disorders.

Comparative anatomy of α2 and β adrenoceptors in the adult and developing brain of the marine teleost the red porgy (Pagrus pagrus, Sparidae): [3H]clonidine and [3H]dihydroalprenolol quantitative autoradiography and receptor subtypes immunohistochemistry

The present study aimed to determine the anatomic distribution and developmental profile of alpha(2) and beta adrenoceptors (AR) in marine teleost brain. Alpha 2 and beta adrenoceptors were studied at different developmental stages by using [(3)H]clonidine and [(3)H]dihydroalprenolol, respectively, by means of in vitro quantitative autoradiography. Furthermore, immunohistochemical localization of the receptor subtypes was performed to determine their cellular distribution. Saturation studies determined a high-affinity component of [(3)H]clonidine and [(3)H]dihydroalprenolol binding sites. High levels of both receptors were found in preglomerular complex, ventral hypothalamus, and lateral torus. Dorsal hypothalamus and isthmus included high levels of alpha(2) AR, whereas pretectum and molecular and proliferative zone of cerebellum were specifically characterized by high densities of beta AR. From the first year of life, adult levels of both AR were found in most medial telencephalic, hypothalamic, and posterior tegmental areas. Decreases in both receptors densities with age were prominent in ventral and posterior telencephalic, pretectal, ventral thalamic, hypothalamic, and tegmental brain regions. Immunohistochemical data were well correlated with autoradiography and demonstrated the presence of alpha(2A), alpha(2C), beta(1), and beta(2) AR subtype-like immunoreactivity. Both the neuronal (perikaryal or dendritic) and the glial localization of receptors was revealed. The localization and age-dependent alterations in alpha(2) and beta AR were parallel to plasticity mechanisms, such as cell proliferation in periventricular thalamus, hypothalamus, and cerebellum. In addition, the biochemical characteristics, distribution pattern, and neuronal or glial specificity of the receptors in teleost brain support a similar profile of noradrenergic transmission in vertebrate brain evolution.

Effects of low dose N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine administration on exploratory and amphetamine-induced behavior and dopamine D2 receptor function in rats with high or low exploratory activity

Individual differences in behavioral traits are associated with sensitivity to various neurochemical and psychopharmacological manipulations. In this study exploratory and amphetamine-induced behavior in rats with persistently high or low exploratory activity (HE and LE, respectively) was examined before and after a partial denervation of the locus coeruleus (LC) projections with the selective neurotoxin DSP-4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine; 10 mg/kg). Partial LC denervation prevented the increase in exploratory activity over repeated test sessions in the LE animals, but had no effect in HE-rats. Amphetamine- (0.5 mg/kg) induced locomotor activity was attenuated by DSP-4 pretreatment only in HE-rats. These results suggest differential involvement of LC noradrenergic transmission in novelty- and amphetamine-induced behavior in animals with persistent differences in novelty-related behavior. In addition to partial noradrenaline depletion in the frontal cortex and hippocampus, which occurred in both HE- and LE-rats, DSP-4 treatment also decreased the content of dopamine and its metabolites in the nucleus accumbens, and the metabolite levels in striatum, but only in the LE-animals. 5-HIAA levels were also reduced in the nucleus accumbens and striatum in LE-rats by the neurotoxin. D(2) receptor function, as determined by dopamine-stimulated [(35)S]GTPgammaS binding, was increased by DSP-4 treatment in the striatum of LE-rats, but reduced in HE-rats. No effect of partial LC denervation was found on dopamine-stimulated [(35)S]GTPgammaS binding in the nucleus accumbens. Together these findings suggest that LC noradrenergic neurotransmission is differently involved in dopaminergic mechanisms which mediate novelty-related vs amphetamine-induced behavior.

Methyl parathion increases neuronal activities in the rat locus coeruleus

Exposure to organophosphate insecticides induces undesirable behavioral changes in humans, including anxiety and irritability, depression, cognitive disturbances and sleep disorders. Little information currently exists concerning the neural mechanisms underlying such behavioral changes. The brain stem locus coeruleus (LC) could be a mediator of organophosphate insecticide-induced behavioral toxicities since it contains high levels of acetylcholinesterase and is involved in the regulation of the sleep-wake cycle, attention, arousal, memory, and pathological processes, including anxiety and depression. In the present study, using a multi-wire recording technique, we examined the effects of methyl parathion, a commonly used organophosphate insecticide, on the firing patterns of LC neurons in rats. Systemic administration of a single dose of methyl parathion (1 mg/kg, i.v.) increased the spontaneous firing rates of LC neurons by 240% but did not change the temporal relationships among the activities of multiple LC neurons. This dose of methyl parathion induced a 50% decrease in blood acetylcholinesterase activity and a 48% decrease in LC acetylcholinesterase activity. The methyl parathion-induced excitation of LC neurons was reversed by administration of atropine sulfate, a muscarinic receptor antagonist, indicating an involvement of muscarinic receptors. The methyl parathion-induced increase in LC neuronal activity returned to normal within 30 min while the blood acetylcholinesterase activity remained inhibited for over 1 h. These data indicate that methyl parathion treatment can elicit excitation of LC neurons. Such excitation could contribute to the neuronal basis of organophosphate insecticide-induced behavioral changes in human.

Increased behavioural activity of rats in forced swimming test after partial denervation of serotonergic system by parachloroamphetamine treatment

The present study aimed at characterizing the effect of partial 5-HT denervation by parachloroamphetamine (PCA), a 5-HT selective neurotoxin, on forced swimming behaviour and monoamine levels in several rat brain regions. PCA was administered intraperitoneally in two independent experiments in doses of 2, 4 and 6 mg/kg and in doses 1, 2, 4 mg/kg, respectively. PCA (2 mg/kg) reduced immobility in the forced swimming test in the Experiment 1 and according to Experiment 2 this is explained by increased swimming time. Dose-dependent reductions in 5-HT and 5-HIAA levels were found in all brain regions studied, and the maximal effects were of a similar magnitude. In septum, the effect of PCA took more time to develop. The effects of the lowest dose of PCA suggest that the neurotoxin affects not only the dorsal raphe projection areas but also the fine axons which arise from the median raphe. alpha2-Adrenoceptors and beta-adrenoceptors in cerebral cortex were not affected by the PCA treatment. Binding affinity of the 5-HT(1A) receptors was higher after all doses of PCA. On the second exposure to the forced swimming the time spent in swimming was found to be negatively and the time spent in immobile posture positively correlated with serotonin turnover in frontal cortex. The time spent in struggling on the second exposure to test was found to be negatively correlated with KD of beta-adrenoceptor binding in cerebral cortex. These data suggest that partial 5-HT denervation with low doses of PCA, which elicits a specific pattern of neurodegeneration, results in an increased behavioural activity, and that the traditional interpretation of the measures in forced swimming test, despite of the test's predictive power in revealing antidepressants acting on monoaminergic systems, is not adequate for studies on the neurochemical basis of depression.

Socioeconomic status and health: a neurobiological perspective

Socioeconomic status (SES) is one of the strongest predictors of health in industrial nations. This is especially true of societies with large disparities between rich and poor. Evidence suggests that the interactions between individuals of different SES play a crucial role in mediating the effects of SES on health. The question is why? Because humans are extremely social animals, their sense of well being is to a large extent determined by their social interactions. In hierarchical societies, individuals at every level of the hierarchy have to submit to those above and the recognition of this submissiveness generates emotions such as shame, anger and depression. These emotions lead to the activation of physiological alarm systems such as the hypothalamic pituitary adrenal axis and the sympathetic nervous system. The chronic activation of these systems alter their set points. This results in changes in the systems' different target organs responsible for diseases such as adult onset diabetes, hypertension, atherosclerosis, major depression and autoimmune diseases. Recent evidence from neurobiology show that one brain area, the amygdala, plays a pivotal role in processing social emotions. Anatomical and physiological studies of the amygdala in animals show how this area could play the central role in activating the alarm systems. This recent evidence brings a deeper level of plausibility to the postulated mechanisms of activation of the alarm systems by social emotions. Other experimental evidence also shed more light on the pathways responsible for translating psychosocial experiences into physiological perturbations.

Stress during gestation induces lasting effects on emotional reactivity of the dam rat

Human and animal studies indicate that repeated stress during pregnancy can produce long-term biological and behavioural disorders in the offspring. In contrast, although maternal stress is supposed to induce an increase of maternal anxiety, few studies have been conducted to demonstrate it. Therefore, in the present study we examined the emotional reactivity in stressed (chronic restraint stress applied 3 x 45 min per day during the last week of pregnancy) and unstressed females rats after the weaning of their pups. Restraint stress procedure reduced the body weight gain both during pregnancy and up to four weeks after the stress period. Stressed dams presented a reduction of exploration and of corticosterone levels when exposed to a novel environment (25 and 49 days post-stress). They spent less time in the open arms of the elevated plus-maze (26 days post-stress). Finally, they showed no increase in the time spent in immobility after a second exposure to the forced-swim test (35-36 days post-stress). In the contrary, such differences were not observed when the chronic stress procedure was applied on virgin females. Overall, our results show that, chronic stress during gestation induces lasting effects on emotional reactivity of the dams, thus indicating that gestation constitutes a critical period in the vulnerability to stressful events also for the mother.

Evaluation of the effect of chronic antidepressant treatment on neurokinin-1 receptor expression in the rat brain

Clinically effective antidepressants are thought to exert their therapeutic effects by facilitating central monoamine neurotransmission. However, recent data showing that neurokinin-1 receptor (NK1R) antagonists have antidepressant properties in both animal and clinical studies raise the possibility that classical antidepressants may also influence NK1R expression in the brain. To test this hypothesis, rats were treated with desipramine, paroxetine, venlafaxine, tranylcypromine or vehicle for 14-42 days. NK1R binding sites and mRNA were determined in a wide variety of brain areas using in situ hybridization and quantitative receptor autoradiography. In all areas examined, the abundance of NK1R binding sites was unchanged after 14 days of treatment. None of the treatments altered the number of NK1R binding sites following 42 days treatment with the exception that an increase was found in the locus coeruleus with tranylcypromine. Taken together, we report that repeated treatment with antidepressants of different classes does not cause significant changes in NK1R expression.