Effects of electroconvulsive treatment on somatostattn, neuropeptide Y, endothelin, and neurokinin a concentrations in cerebrospinal fluid of depressed patients: A pilot study

Effect of depression and suicidal behavior on neuropeptide Y (NPY) and its receptors in the adult human brain: A postmortem study

Neuropeptides are small proteinaceous molecules (3-100 amino acids) that are secreted by neurons and act on both neuronal and non-neuronal cells. Neuropeptide Y (NPY), a highly conserved and expressed neuropeptide in the central nervous system of mammals, plays a major role in stress response and resilience. Increasing evidence suggests that NPY and its receptors are altered in depression and suicide, pointing to their antidepressant-like nature. The objective of this study was to examine the role of NPY system in depression and suicidal behavior. Expression of NPY and its four receptors, NPY1R, NPY2R, NPY4R, and NPY5R was studied at the transcriptional and translational levels in the prefrontal cortex (PFC) and hippocampus regions of the postmortem brain of normal control (NC) (n = 24) and depressed suicide (DS) (n = 24) subjects. We observed a significant decrease in NPY mRNA and upregulation in NPY1R and NPY2R mRNA in both brain regions of DS subjects compared with NC subjects. We also observed a significant decrease in NPY protein expression in the PFC of subjects with DS. This study provides the first detailed evidence of alterations in the NPY system and the associated stress response in depression and suicidal behavior in humans. The outcomes of this study could be applied in the development of novel NPY system-targeted approaches for the treatment of depression.

A Randomized Controlled Trial of Intranasal Neuropeptide Y in Patients With Major Depressive Disorder

BACKGROUND

Since about one-third of patients with major depressive disorder (MDD) do not respond adequately to available antidepressants, there is a need for treatments based on novel mechanisms of action. Neuropeptide Y (NPY), a normal brain constituent, is reduced in cerebrospinal fluid of patients with MDD and post-traumatic stress disorder and in corresponding rodent models. Moreover, NPY administered centrally or intranasally rescues pathophysiology in these models. Consequently, we conducted the first, to our knowledge, controlled trial of NPY as a treatment for MDD.

METHODS

Thirty MDD patients on a stable dose of a conventional antidepressant insufflated 6.8 mg NPY (n = 12) or placebo (n = 18) in a double blind randomized fashion. Effects were assessed at baseline, +1 hour, +5 hours, +24 hours, and +48 hours. The primary outcome was change in depression severity measured with the Montgomery-Åsberg Depression Rating Scale (MADRS).

RESULTS

NPY was superior to placebo at +24 hours (change -10.3 [95% CI: -13.8; -6.8]) vs -5.6 (95% CI: -8.4; -2.7); group*time F = 3.26, DF = (1,28), P = .04; Cohen's d = 0.67). At +5 hours MADRS decreased -7.1 ([95% CI: -10.0; -4.2] vs -3.5 [95% CI: -5.8; -1.2]; group*time F = 2.69, DF = (1,28), P = .05; Cohen's d = 0.61). MADRS reduction at +48 hours was not significant.

CONCLUSIONS

Since no results regarding the trajectory of NPY effects existed prior to this study we extrapolated from the known NPY biology and predicted the effects will occur 5-48 hours post insufflation. We chose +48 hours as the primary endpoint and +1, +5, and +24 hours as secondary endpoints. The results, the first of their kind, indicate that insufflated NPY is antidepressant, despite not meeting the primary outcome, and call for dose ranging and repeated NPY insufflation trials.

CLINICAL TRIAL REGISTRATION

EudraCT Number: 2014-000129-19.

Differential plastic changes in synthesis and binding in the mouse somatostatin system after electroconvulsive stimulation

OBJECTIVE

Electroconvulsive therapy (ECT) is regularly used to treat patients with severe major depression, but the mechanisms underlying the beneficial effects remain uncertain. Electroconvulsive stimulation (ECS) regulates diverse neurotransmitter systems and induces anticonvulsant effects, properties implicated in mediating therapeutic effects of ECT. Somatostatin (SST) is a candidate for mediating these effects because it is upregulated by ECS and exerts seizure-suppressant effects. However, little is known about how ECS might affect the SST receptor system. The present study examined effects of single and repeated ECS on the synthesis of SST receptors (SSTR1-4) and SST, and SST receptor binding ([125I]LTT-SST28) in mouse hippocampal regions and piriform/parietal cortices.

RESULTS

A complex pattern of plastic changes was observed. In the dentate gyrus, SST and SSTR1 expression and the number of hilar SST immunoreactive cells were significantly increased at 1 week after repeated ECS while SSTR2 expression was downregulated by single ECS, and SSTR3 mRNA and SST binding were elevated 24 h after repeated ECS. In hippocampal CA1 and parietal/piriform cortices, we found elevated SST mRNA levels 1 week after repeated ECS and elevated SST binding after single ECS and 24 h after repeated ECS. In hippocampal CA3, repeated ECS increased SST expression 1 week after and SST binding 24 h after. In the parietal cortex, SSTR2 mRNA expression was downregulated after single ECS while SSTR4 mRNA expression was upregulated 24 h after repeated ECS.

CONCLUSION

Considering the known anticonvulsant effects of SST, it is likely that these ECS-induced neuroplastic changes in the SST system could participate in modulating neuronal excitability and potentially contribute to therapeutic effects of ECT.

Diurnal fluctuations in HPA and neuropeptide Y-ergic systems underlie differences in vulnerability to traumatic stress responses at different zeitgeber times

The hypothalamic-pituitary-adrenal (HPA) axis displays a characteristic circadian pattern of corticosterone release, with higher levels at the onset of the active phase and lower levels at the onset of the inactive phase. As corticosterone levels modify the response to stress and influence the susceptibility to and/or severity of stress-related sequelae, we examined the effects of an acute psychological trauma applied at different zeitgeber times (ZTs) on behavioral stress responses. Rats were exposed to stress either at the onset of the inactive-(light) phase (ZT=0) or at the onset of the active-(dark) phase (ZT=12). Their behavior in the elevated plus-maze and acoustic startle response paradigms were assessed 7 days post exposure for retrospective classification into behavioral response groups. Serum corticosterone levels and the dexamethasone suppression test were used to assess the stress response and feedback inhibition of the HPA axis. Immunoreactivity for neuropeptide Y (NPY) and NPY-Y1 receptor (Y1R) in the paraventricular (PVN) and arcuate (ARC) hypothalamic nuclei, hippocampus, and basolateral amygdala were measured. The behavioral effects of NPY/Y1R antagonist microinfused into the PVN 30 min before stress exposure during the inactive or active phase, respectively, were evaluated. PVN immunoreactivity for NPY and Y1R was measured 1 day after the behavioral tests. The time of day of the traumatic exposure markedly affected the pattern of the behavioral stress response and the prevalence of rats showing an extreme behavioral response. Rats exposed to the stressor at the onset of their inactive phase displayed a more traumatic behavioral response, faster post-exposure corticosterone decay, and a more pronounced stress-induced decline in NPY and Y1R expression in the PVN and arcuate hypothalamic nuclei. Blocking PVN Y1R before stress applied in the active phase, or administering NPY to the PVN before stress applied in the inactive phase, had a resounding behavioral effect. The time at which stress occurred significantly affected the behavioral stress response. Diurnal variations in HPA and NPY/Y1R significantly affect the behavioral response, conferring more resilience at the onset of the active phase and more vulnerability at the onset of the inactive phase, implying that NPY has a significant role in conferring resilience to stress-related psychopathology.

Targeting the Neuropeptide Y System in Stress-related Psychiatric Disorders

Repeated, extreme, or traumatic stressors can elicit pathological effects leading to many negative physical and psychological outcomes. Stressors can precipitate the onset of psychiatric diseases, or exacerbate pre-existing disorders including various anxiety and mood disorders. As stressors can negatively impact human psychiatric health, it is essential to identify neurochemicals that may confer protection from the negative sequelae of repeated or extreme stress exposure. Elucidating the neurobiological underpinnings of stress resilience will enhance our ability to promote resilience to, or recovery from, stress-related psychiatric disease. Herein, we will review the evidence for neuropeptide Y as an endogenous mediator of resilience and its potential relevance for the treatment of stress-related psychiatric diseases.

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Overview of neuropeptide Y and receptor subtypes in the central nervous system.

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Alterations of neuropeptide Y in human stress-related psychiatric disorders.

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Evidence for neuropeptide Y in resilience to stress-related emotionality in rodent behavioral models.

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Pharmacotherapeutic implications for neuropeptide Y in the treatment of stress-related psychiatric disorders.

Low neuropeptide Y in cerebrospinal fluid in bipolar patients is associated with previous and prospective suicide attempts

The attempted and accomplished suicide rates in patients with bipolar disorder are 40-50% and 15-20%, respectively. No biological markers that help predict suicide been identified. Human and experimental animal data indicate that dysregulation of the neuropeptide Y (NPY) system plays a role in depression, anxiety, and posttraumatic stress disorder (PTSD). The aim of this study was to explore if low cerebrospinal fluid (CSF) NPY is associated with (1) past suicide attempts, (2) future suicide attempts, and (3) trait anxiety. Lumbar puncture was performed on 120 clinically stable patients with bipolar disorder enrolled in the St Göran Bipolar Project, where the number of previous suicide attempts was documented. NPY-like immunoreactivity (NPY-LI) was determined in cerebrospinal fluid (CSF). Patients were reexamined one year after the lumbar puncture and suicide attempts were recorded. NPY-LI was significantly lower in patients with a history of suicide attempt than in patients who had not attempted suicide prior to lumbar puncture. Importantly, NPY-LI was markedly lower in patients who made a suicide attempt during the follow-up period compared to patients who did not. Patients who attempted suicide during the follow-up also had markedly lower NPY-LI than those with previous suicide attempts who did not reattempt. Our results suggest that low CSF NPY-LI predicts future suicide attempts. The data are in line with the hypothesis that NPY signaling is altered in affective disorders and states of emotional dysregulation.

The neuropeptide Y (NPY)-ergic system is associated with behavioral resilience to stress exposure in an animal model of post-traumatic stress disorder

Converging evidence implicates the regulatory neuropeptide Y (NPY) in anxiety- and depression-related behaviors. The present study sought to assess whether there is an association between the magnitude of behavioral responses to stress and patterns of NPY in selected brain areas, and subsequently, whether pharmacological manipulations of NPY levels affect behavior in an animal model of PTSD. Animals were exposed to predator-scent stress for 15 min. Behaviors were assessed with the elevated plus maze and acoustic startle response tests 7 days later. Preset cutoff criteria classified exposed animals according to their individual behavioral responses. NPY protein levels were assessed in specific brain regions 8 days after the exposure. The behavioral effects of NPY agonist, NPY-Y1-receptor antagonist, or placebo administered centrally 1 h post-exposure were evaluated in the same manner. Immunohistochemical technique was used to detect the expression of the NPY, NPY-Y1 receptor, brain-derived neurotrophic factor, and GR 1 day after the behavioral tests. Animals whose behavior was extremely disrupted (EBR) selectively displayed significant downregulation of NPY in the hippocampus, periaqueductal gray, and amygdala, compared with animals whose behavior was minimally (MBR) or partially (PBR) disrupted, and with unexposed controls. One-hour post-exposure treatment with NPY significantly reduced prevalence rates of EBR and reduced trauma-cue freezing responses, compared with vehicle controls. The distinctive pattern of NPY downregulation that correlated with EBR as well as the resounding behavioral effects of pharmacological manipulation of NPY indicates an intimate association between NPY and behavioral responses to stress, and potentially between molecular and psychopathological processes, which underlie the observed changes in behavior. The protective qualities attributed to NPY are supported by the extreme reduction of its expression in animals severely affected by the stressor and imply a role in promoting resilience and/or recovery.

Analytical methods for brain targeted delivery system in vivo: perspectives on imaging modalities and microdialysis

Since the introduction of microdialysis in 1974, the semi-invasive analytical method has grown exponentially. Microdialysis is one of the most potential analysis technologies of pharmacological drug delivery to the brain. In recent decades, analysis of chemicals targeting the brain has led to many improvements. It seems likely that fluorescence imaging was limited to ex vivo and in vitro applications with the exception of several intravital microscopy and photographic imaging approaches. X-ray computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) have been commonly utilized for visualization of distribution and therapeutic effects of drugs. The efficient analytical methods for studies of brain-targeting delivery system is a major challenge in detecting the disposition as well as the variances of the factors that regulate the substances delivery into the brain. In this review, we highlight some of the ongoing trends in imaging modalities and the most recent developments in the field of microdialysis of live animals and present insights into exploiting brain disease for therapeutic and diagnostics purpose.

Animal models of depression and anxiety: What do they tell us about human condition?

While modern neurobiology methods are necessary they are not sufficient to elucidate etiology and pathophysiology of affective disorders and develop new treatments. Achievement of these goals is contingent on applying cutting edge methods on appropriate disease models. In this review, the authors present four rodent models with good face-, construct-, and predictive-validity: the Flinders Sensitive rat line (FSL); the genetically "anxious" High Anxiety-like Behavior (HAB) line; the serotonin transporter knockout 5-HTT(-/-) rat and mouse lines; and the post-traumatic stress disorder (PTSD) model induced by exposure to predator scent, that they have employed to investigate the nature of depression and anxiety.

Quetiapine and norquetiapine in plasma and cerebrospinal fluid of schizophrenic patients treated with quetiapine: correlations to clinical outcome and HVA, 5-HIAA, and MHPG in CSF

This study investigated concentrations of quetiapine and norquetiapine in plasma and cerebrospinal fluid (CSF) in 22 schizophrenic patients after 4-week treatment with quetiapine (600 mg/d), which was preceded by a 3-week washout period. Blood and CSF samples were obtained on days 1 and 28, and CSF levels of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) concentrations were measured at baseline and after 4 weeks of quetiapine, allowing calculations of differences in HVA (ΔHVA), 5-HIAA (Δ5-HIAA), and MHPG (ΔMHPG) concentrations. Patients were assessed clinically, using the Positive and Negative Syndrome Scale (PANSS) and Clinical Global Impression Scale at baseline and then at weekly intervals. Plasma levels of quetiapine and norquetiapine were 1110 ± 608 and 444 ± 226 ng/mL, and the corresponding CSF levels were 29 ± 18 and 5 ± 2 ng/mL, respectively. After the treatment, the levels of HVA, 5-HIAA, and MHPG were increased by 33%, 35%, and 33%, respectively (P < 0.001). A negative correlation was found between the decrease in PANSS positive subscale scores and CSF ΔHVA (r(rho) = -0.690, P < 0.01), and the decrease in PANSS negative subscale scores both with CSF Δ5-HIAA (r(rho) = -0.619, P = 0.02) and ΔMHPG (r(rho) = -0.484, P = 0.038). Because, unfortunately, schizophrenic patients experience relapses even with the best available treatments, monitoring of CSF drug and metabolite levels might prove to be useful in tailoring individually adjusted treatments.

The antidepressant effects of running and escitalopram are associated with levels of hippocampal NPY and Y1 receptor but not cell proliferation in a rat model of depression

One hypothesis of depression is that it is caused by reduced neuronal plasticity including hippocampal neurogenesis. In this study, we compared the effects of three long-term antidepressant treatments: escitalopram, voluntary running, and their combination on hippocampal cell proliferation, NPY and the NPY-Y1 receptor mRNAs, targets assumed to be important for hippocampal plasticity and mood disorders. An animal model of depression, the Flinders Sensitive Line (FSL) rat, was used and female rats were chosen because the majority of the depressed population is females. We investigated if these treatments were correlated to immobility, swimming, and climbing behaviors, which are associated with an overall, serotonergic-like and noradrenergic-like antidepressant response, in the Porsolt swim test (PST). Interestingly, while escitalopram, running and their combination increased the number of hippocampal BrdU immunoreactive cells, the antidepressant-like effect was only detected in the running group and the group with access both to running wheel and escitalopram. Hippocampal NPY mRNA and the NPY-Y1 receptor mRNA were elevated by running and the combined treatment. Moreover, correlations were detected between NPY mRNA levels and climbing and cell proliferation and NPY-Y1 receptor mRNA levels and swimming. Our results suggest that increased cell proliferation is not necessarily associated with an antidepressant effect. However, treatments that were associated with an antidepressant-like effect did regulate hippocampal levels of mRNAs encoding NPY and/or the NPY-Y1 receptor and support the notion that NPY can stimulate cell proliferation and induce an antidepressant-like response.

Effects of prolonged ethanol vapor exposure on forced swim behavior, and neuropeptide Y and corticotropin-releasing factor levels in rat brains

Depressive symptoms in alcohol-dependent individuals are well-recognized and clinically relevant phenomena. The etiology has not been elucidated although it is clear that the depressive symptoms may be alcohol independent or alcohol induced. To contribute to the understanding of the neurobiology of chronic ethanol use, we investigated the effects of chronic intermittent ethanol vapor exposure on behaviors in the forced swim test (FST) and neuropeptide Y (NPY) and corticotropin-releasing factor (CRF) levels in specific brain regions. Adult male Wistar rats were subjected to intermittent ethanol vapor (14 h on/10 h off) or air exposure for 2 weeks and were then tested at three time points corresponding to acute withdrawal (8-12 h into withdrawal) and protracted withdrawal (30 and 60 days of withdrawal) in the FST. The behaviors that were measured in the five-min FST consisted of latency to immobility, swim time, immobility time, and climbing time. The FST results showed that the vapor-exposed animals displayed depressive-like behaviors; for instance, decreased latency to immobility in acute withdrawal and decreased latency to immobility, decreased swim time and increased immobility time in protracted withdrawal, with differences between air- and vapor-exposed animals becoming more pronounced over the 60-day withdrawal period. NPY levels in the frontal cortex of the vapor-exposed animals were decreased compared with the control animals, and CRF levels in the amygdala were correlated with increased immobility time. Thus, extended ethanol vapor exposure produced long-lasting changes in FST behavior and NPY levels in the brain.

Acute stress differentially affects corticotropin-releasing hormone mRNA expression in the central amygdala of the "depressed" flinders sensitive line and the control flinders resistant line rats

Preclinical and clinical evidence suggests that neuropeptides play a role in the pathophysiology of mood disorders. In the present study, we investigated the involvement of the peptides corticotropin-releasing hormone (CRH), neuropeptide Y (NPY) and nociceptin/orphanin FQ (N/OFQ) and of their receptors in the regulation of emotional behaviours. In situ hybridization experiments were performed in order to evaluate the mRNA expression levels of these neuropeptidergic systems in limbic and limbic-related brain regions of the Flinders Sensitive Line (FSL) rats, a putative genetic animal model of depression. The FSL and their controls, the Flinders Resistant Line (FRL) rats, were subjected to one hour acute restraint and the effects of the stress exposure, including possible strain specific changes on these neuropeptidergic systems, were studied. In basal conditions, no significant differences between FSL and FRL rats in the CRH mRNA expression were found, however an upregulation of the CRH mRNA hybridization signal was detected in the central amygdala of the stressed FRL, compared to the non stressed FRL rats, but not in the FSL, suggesting a hypoactive mechanism of response to stressful stimuli in the "depressed" FSL rats. Baseline levels of NPY and N/OFQ mRNA were lower in the FSL rats compared to the FRL in the dentate gyrus of hippocampus and in the medial amygdala, respectively. However, the exposure to stress induced a significant upregulation of the N/OFQ mRNA levels in the paraventricular thalamic nucleus, while in the same nucleus the N/OFQ receptor mRNA expression was higher in the FSL rats. In conclusion, selective alterations of the NPY and N/OFQ mRNA in limbic and limbic-related regions of the FSL rats, a putative animal model of depression, provide further support for the involvement of these neuropeptides in depressive disorders. Moreover, the lack of CRH activation following stress in the "depressed" FSL rats suggests a form of allostatic load, that could alter their interpretation of environmental stimuli and influence their behavioural response to stressful situations.

Infusion of neuropeptide Y into CA3 region of hippocampus produces antidepressant-like effect via Y1 receptor

A couple of papers indicate that patients with depression show a decrease in serum neuropeptide Y (NPY). To study the role of NPY in depression, we examined the effects of infusion of NPY into the hippocampus of learned helplessness (LH) rats (an animal model of depression). Infusion of NPY into the cerebral ventricle of LH rats showed antidepressant-like effects. Infusion of NPY into the CA3 region, but not the dentate gyrus (DG), produced antidepressant-like effects in the LH paradigm. Infusion of NPY did not affect locomotor activity or aversive learning ability. Coadministration of BIBO3304 (a Y1 receptor antagonist) with NPY to the CA3 region blocked the antidepressant-like effects of NPY, whereas coadministration of NPY with BIIE0246 (a Y2 receptor antagonist) to the CA3 region failed to block antidepressant-like effects. Furthermore, infusions of [Leu(31) Pro(34)]PYY (a Y1 and Y5 receptor agonist) alone and BIIE0246 alone into the CA3 region produced the antidepressant-like effects in LH rats. These results suggest that infusion of NPY into the CA3 region of hippocampus of LH rats produces antidepressant-like activity through Y1 receptors and attenuating effects through Y2 receptors.

Search for biological correlates of depression and mechanisms of action of antidepressant treatment modalities. Do neuropeptides play a role?

Dysregulation of the monoaminergic systems is likely a sufficient but not a necessary cause of depression. A wealth of data indicates that neuropeptides, e.g., NPY, CRH, somatostatin, tachykinins and CGRP play a role in affective disorders and alcohol use/abuse. This paper focuses on NPY in etiology and pathophysiology of depression. Decreased peptide and mRNA NPY were found in hippocampus of both the genetic, e.g., the FSL strain, and environmental rat models of depression, e.g., chronic mild stress and early life maternal separation paradigms. Rat models of alcoholism also show altered NPY. Furthermore, NPY is also reduced in CSF of depressed patients. Antidepressive treatments tested so far (lithium, topiramate, SSRIs, ECT and ECS, wheel running) increase NPY selectively in rat hippocampus and in human CSF. Moreover, NPY given icv to rat has antidepressive effects which are antagonized by NPY-Y1 blockers. The data support our hypothesis that the NPY system dysregulation constitutes one of the biological underpinnings of depression and that one common mechanism of action of antidepressive treatment modalities may be effects on NPY and its receptors. In a novel paradigm, early life maternal separation was superimposed on "depressed" FSL and control rats and behavioral and brain neurochemistry changes observed in adulthood. The consequences were more deleterious in genetically vulnerable FSL. Early antidepressive treatment modulated the adult sequelae. Consequently, if these data are confirmed, the ethical and medical question that will be asked is whether it is permissible and advisable to consider prophylactically treating persons at risk.

Electroconvulsive stimuli selectively affect behavior and neuropeptide Y (NPY) and NPY Y(1) receptor gene expressions in hippocampus and hypothalamus of Flinders Sensitive Line rat model of depression

Previously we reported that basal neuropeptide Y (NPY)-like immunoreactivity-(LI) in hippocampus of the "depressed" Flinders Sensitive Line (FSL) rats was lower compared to the control Flinders Resistant Line (FRL) and that electroconvulsive stimuli (ECS) raise NPY-LI in discrete brain regions. Here we studied NPY mRNA expression, NPY Y(1) receptor (Y(1)) mRNA expression and binding sites, and behavior under basal conditions (Sham) and after repeated ECS. Baseline NPY and Y(1) mRNAs in the CA1-2 regions and dentate gyrus were lower while the Y(1) binding was higher in the FSL. ECS had larger effects on both NPY and behavior in the FSL rats. ECS increased NPY mRNA in the CA1-2, dentate gyrus and hypothalamus in FSL, but only in the dentate gyrus in FRL. ECS also increased Y(1) mRNA in the CA1-2, dentate gyrus and the parietal cortex in both strains, while in the hypothalamus the increase was observed only in the FSL rats. Consistently with Y(1) mRNA increase, Y(1) binding was downregulated in the corresponding regions. ECS decreased FSL immobility in the Porsolt swim test. These findings suggest that NPY is involved in depressive disorder and that antidepressant effects of ECS may in part be mediated through NPY.

Effects of acute and subchronic d-amphetamine on ventral striatal concentrations of neurotensin and neuropeptide Y in rats treated with antipsychotic drugs

We have reported that acute d-amphetamine increases extracellular concentrations (efflux) of neurotensin-like immunoreactivity (NT-LI) and neuropeptide Y-LI (NPY-LI) in the ventral striatum (VSTR) of freely moving rats, effects that are abolished by chronic administration of haloperidol and risperidone admixed to food pellets. In this study we further investigated the d-amphetamine effects on NT-LI and NPY-LI efflux in VSTR and their content in selected brain regions. Rats received haloperidol, risperidone or vehicle for 30days and saline or d-amphetamine either on days 22-29 and/or day 30. Seven day d-amphetamine administration decreased basal NT-LI and NPY-LI efflux in vehicle-treated rats; pretreatment with haloperidol counteracted these effects, while pretreatment with risperidone had effect only on NT-LI. Acute d-amphetamine after the seven day d-amphetamine increased NT-LI only. Pretreatment with haloperidol or risperidone abolished the effects of acute d-amphetamine on NT-LI and NPY-LI. Acute and seven day d-amphetamine increased NT-LI and NPY-LI contents in striatum; seven day d-amphetamine also increased NT-LI in frontal and occipital cortex and both NT-LI and NPY-LI in hippocampus. Our results suggest that NT and NPY are involved in both the pathophysiology and the therapeutics of schizophrenia.

Effects of maternal separation on neuropeptide Y and calcitonin gene-related peptide in "depressed" Flinders Sensitive Line rats: a study of gene-environment interactions

Interactions between genetic vulnerability to stress/depression and early life experience may play a crucial role in the pathogenesis of mood disorders. Here we explore this hypothesis by superimposing early life trauma in the form of maternal deprivation for 180 min per day from postnatal day 2 to 14 onto a genetic model of depression/susceptibility to depression, Flinders Sensitive Line (FSL) and their controls, Flinders Resistant Line (FRL) rats. We investigate effects on neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) like immunoreactivity (LI) in 10 brain regions as these neuropeptides are affected by antidepressants and are altered in cerebrospinal fluid of depressed patients. NPY-LI was reduced while CGRP-LI was elevated in hippocampus and frontal cortex of "genetically depressed" FSL rats. The two peptides displayed a significant negative correlation in these regions that was strongest in the FSL strain. Maternal deprivation exacerbated the strain difference in hippocampal CGRP-LI, while it was without effect on NPY-LI. FSL rats had higher tissue concentration of both neuropeptides in periaqueductal grey and higher NPY-LI in caudate/putamen. Maternal deprivation selectively raised CGRP-LI in amygdala of the FRL control stain. Thus, in two brain regions implicated in the neurobiology of depression, hippocampus and frontal cortex, changes in CGRP-LI and NPY-LI were in opposite direction, and CGRP-LI appears to be more responsive to adverse experience. Our findings thus support the hypothesis that genetic disposition and developmental stress may contribute to the susceptibility to depression by exerting selective neuropeptide- and brain region-specific effects on adult neurobiology.

Running has differential effects on NPY, opiates, and cell proliferation in an animal model of depression and controls

Physical activity has documented beneficial effect in treatment of depression. Recently, we found an antidepressant-like effect of running in an animal model of depression, the Flinders Sensitive Line (FSL) and demonstrated that it was associated with increased hippocampal cell proliferation. In this study, we analyzed levels of mRNAs encoding the neuropeptide Y (NPY) and the opioid peptides dynorphin and enkephalin in hippocampus and correlated these to cell proliferation in the FSL and in the 'nondepressed' Flinders Resistant Line (FRL) strain, with/without access to running wheels. Running increased NPY mRNA in dentate gyrus and the CA4 region in FSL, but not in FRL rats. NPY mRNA increase was correlated to increased cell proliferation in the subgranular zone of dentate gyrus. Baseline dynorphin and enkephalin mRNA levels in the dentate gyrus were lower in the FSL compared to the FRL strain. Running had no effect on dynorphin and enkephalin mRNAs in the FSL strain but it decreased dynorphin mRNA, and there was a trend to increased enkephalin mRNA in the FRL rats. Thus, it would appear that the CNS effects of running are different in 'depressed' and control animals; modification of NPY, a peptide associated with depression and anxiety, in depressed animals, vs effects on opioids, associated with the reward systems, in healthy controls. Our data support the hypothesis that NPY neurotransmission in hippocampus is malfunctioning in depression and that antidepressive treatment, in this case wheel running, will normalize it. In addition, we also show that the increased NPY after running is correlated to increased cell proliferation, which is associated with an antidepressive-like effect.

Exacerbated loss of cell survival, neuropeptide Y-immunoreactive (IR) cells, and serotonin-IR fiber lengths in the dorsal hippocampus of the aged flinders sensitive line “depressed” rat: Implications for the pathophysiology of depression?

Impairment of hippocampal neurogenesis has been proposed to provide a cellular basis for the development of major depression. Studies have shown that serotonin (5-HT) and neuropeptide Y (NPY) may be involved in stimulating cell proliferation in the dentate gyrus. The Flinders-sensitive line (FSL) rat represents a genetic model of depression with characterized 5-HT and NPY abnormalities in the hippocampus. Consequently, it could be hypothesized that hippocampal neurogenesis in the FSL rat would be impaired. The present study examined the relationship among 1) number of BrdU-immunoreactive (IR) cells, 2) NPY-IR cells in the dentate gyrus, and 3) length of 5-HT-IR fibers in the dorsal hippocampus, as well as volume and number of 5-HT-IR cells in the dorsal raphé nucleus, in adult and aged FSL rats and control Flinders-resistant line (FRL) rats. Surprisingly, adult FSL rats had significantly more BrdU-IR and NPY-IR cells compared with adult FRL rats. However, aging caused an exacerbated loss of these cell types in the FSL strain compared with FRL. The aged FSL rats also had shortened 5-HT-IR fibers in the dorsal hippocampus, indicative of an impaired 5-HT innervation of this area, compared with FRL. These results suggest that, for "depressed" FSL rats, compared with FRL rats, aging is associated with an excacerbated loss of newly formed cells in addition to NPY-IR cells and 5-HT-IR dendrites in the hippocampus. These observations may be of relevance to the depression-like behavior of the FSL rat and, by inference, to the pathophysiology of depression.

Recent advances in the development of treatments for alcohol and cocaine dependence: focus on topiramate and other modulators of GABA or glutamate function

Neuroscientific developments have promulgated interest in developing efficacious medications for the treatment of substance dependence. Previous pharmacological strategies that involve the use of relatively specific medications to alter corticomesolimbic dopaminergic neuronal activity--the critical pathway for expression of the reinforcing effects of abused drugs--have yielded modest efficacy in the treatment of alcohol dependence, and no medication has been established as a treatment for cocaine dependence. Since corticomesolimbic dopaminergic neurons interact with other neurotransmitters that modulate the effects of dopamine in the nucleus accumbens, would it not be possible to control these dopaminergic effects more reliably with a medication that acts contemporaneously on more than one neuromodulator of dopaminergic function? Further, since the long-term use of either alcohol or cocaine results in neuronal adaptations as a result of sensitisation, would the chances of effective therapy not be bolstered by administering a medication that was also able to mitigate these chronic effects? Thus, a new conceptual approach is needed. My proposal is that a medication--in this case topiramate--that principally potentiates inhibitory GABA(A) receptor-mediated input and antagonises excitatory glutamatergic afferents to the corticomesolimbic dopaminergic system should have therapeutic potential in treating either alcohol or cocaine dependence or perhaps both. This is because the principal neurochemical effects of topiramate would not only serve to decrease the acute reinforcing effects of alcohol or cocaine, but might also facilitate cessation of their use following a period of long-term use by decreasing neuronal sensitisation. This overview highlights the scientific concepts and clinical evidence for the development of topiramate in the treatment of alcohol dependence and introduces preliminary evidence to indicate that it might also have utility in treating cocaine dependence. Finally, to place the material on topiramate in context, information has been included on the utility and development of other medications that modulate GABA- or glutamate-mediated neuronal systems for the treatment of alcohol or cocaine dependence.

Long-term citalopram administration reduces responsiveness of HPA axis in patients with major depression: relationship with S-citalopram concentrations in plasma and cerebrospinal fluid (CSF) and clinical response

RATIONALE

A dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is a well-documented neurobiological finding in major depression. Moreover, clinically effective therapy with antidepressant drugs may normalize the HPA axis activity.

OBJECTIVE

The aim of this study was to test whether citalopram (R/S-CIT) affects the function of the HPA axis in patients with major depression (DSM IV).

METHODS

Twenty depressed patients (11 women and 9 men) were challenged with a combined dexamethasone (DEX) suppression and corticotropin-releasing hormone (CRH) stimulation test (DEX/CRH test) following a placebo week and after 2, 4, and 16 weeks of 40 mg/day R/S-CIT treatment.

RESULTS

The results show a time-dependent reduction of adrenocorticotrophic hormone (ACTH) and cortisol response during the DEX/CRH test both in treatment responders and nonresponders within 16 weeks. There was a significant relationship between post-DEX baseline cortisol levels (measured before administration of CRH) and severity of depression at pretreatment baseline. Multiple linear regression analyses were performed to identify the impact of psychopathology and hormonal stress responsiveness and R/S-CIT concentrations in plasma and cerebrospinal fluid (CSF). The magnitude of decrease in cortisol responsivity from pretreatment baseline to week 4 on drug [delta-area under the curve (AUC) cortisol] was a significant predictor (p<0.0001) of the degree of symptom improvement following 16 weeks on drug (i.e., decrease in HAM-D21 total score). The model demonstrated that the interaction of CSF S-CIT concentrations and clinical improvement was the most powerful predictor of AUC cortisol responsiveness.

CONCLUSION

The present study shows that decreased AUC cortisol was highly associated with S-CIT concentrations in plasma and CSF. Therefore, our data suggest that the CSF or plasma S-CIT concentrations rather than the R/S-CIT dose should be considered as an indicator of the selective serotonergic reuptake inhibitors (SSRIs) effect on HPA axis responsiveness as measured by AUC cortisol response.

Subchronic treatment with imipramine ameliorates the decreased number in neuropeptide Y-positive cells in the hippocampus of learned helplessness rats

Learned helplessness, but not immobilization stress, decreased the numbers of neuropeptide Y (NPY)-positive cells (interneuron), but not calcitonin gene-related peptide (CGRP)-positive cells (mossy cell), in the hilus of the hippocampus. Subchronic treatment of learned helplessness rats, but not naive rats, with imipramine ameliorated the decrease in the number of NPY-positive cells. Therefore, NPY-positive cells in the hippocampus may contribute to depression.

Topiramate normalizes hippocampal NPY-LI in flinders sensitive line 'depressed' rats and upregulates NPY, galanin, and CRH-LI in the hypothalamus: implications for mood-stabilizing and weight loss-inducing effects

Topiramate is currently used in the treatment of epilepsy, but this anticonvulsant drug has also been reported to exert mood-stabilizing effects and induce weight loss in patients. Neuropeptide Y (NPY) is abundantly and widely distributed in the mammalian central nervous system and centrally administered NPY markedly reduces pharmacologically induced seizures and induces antidepressant-like activity as well as feeding behavior. Two other peptides, galanin and corticotropin-releasing hormone (CRH), have also been proposed to play a modulatory role in mood, appetite, and seizure regulation. Consequently, we investigated the effects of single and repeated topiramate (10 days, once daily: 40 mg/kg i.p.) or vehicle treatment in 'depressed' flinders sensitive line (FSL) and control Flinders resistant line (FRL) rats on brain regional peptide concentrations of NPY, galanin, and CRH. The handling associated with repeated injections reduced hippocampal levels of NPY- and galanin-like immunoreactivities (LI) while NPY- and CRH-LI levels were increased in the hypothalamus, regardless of strain or treatment. In the hippocampus, concentrations of NPY-LI, galanin-LI, and CRH-LI were lower in FSL than FRL animals. Repeated topiramate treatment selectively normalized NPY-LI in this region in the FSL animals. In the hypothalamus, galanin-LI was reduced in FSL compared to FRL animals. Topiramate elevated the hypothalamic concentrations of NPY-LI, CRH-LI, and galanin-LI in both strains. Furthermore, topiramate elevated serum leptin but not corticosterone levels. The present findings show that topiramate has distinct effects on abnormal hippocampal levels of NPY, with possible implications for its anticonvulsant and mood-stabilizing effects. Furthermore, stimulating hypothalamic NPY-LI, CRH-LI and galanin-LI as well as serum leptin levels may be associated with the weight loss-inducing effects of topiramate.

Putative common pathways in therapeutic brain stimulation for affective disorders

Brain stimulation methods in the treatment of affective disorder are electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS). Clinically, ECT is considered the strongest remedy in the treatment of severe depression, especially depression with psychotic features, and in the elderly. TMS, despite positive reports, is somewhat more controversial. VNS has, so far, only been used in treatment-resistant depression with limited results. DBS may be of potential use in rare cases of treatment-resistant cases of affective disorder. This article highlights the similarities and differences between the four stimulation methods. The main difference is the seizures necessary in ECT. A stronger involvement of the hippocampus following experimental seizures compared with effects in that region induced by TMS and VNS might explain the consistent findings of the superiority of ECT in the most severe cases of affective disorder.

Neuropeptide Y (NPY) and depression: from animal studies to the human condition

Neuropeptide Y (NPY) is widely distributed throughout the central nervous system (CNS) and is one of the most conserved peptides in evolution, suggesting an important role in the regulation of basic physiological functions. In addition, both pre-clinical and clinical evidence have suggested that NPY, together with its receptors, may have a direct implication in several psychiatric disorders, including depression and related illnesses. NPY-like immunoreactivity and NPY receptors are expressed throughout the brain, with varying concentrations being found throughout the limbic system. Such brain structures have been repeatedly implicated in the modulation of emotional processing, as well as in the pathogenesis of depressive disorders. This review will concentrate on the distribution of NPY, its receptors, and the putative role played by this peptide in depressive illness based on both pre-clinical and clinical evidence.

Early maternal separation alters neuropeptide Y concentrations in selected brain regions in adult rats

Human and animal studies support the involvement of neuropeptide Y (NPY) in the pathophysiology of depression. Thus, hippocampal NPY-LI is decreased in genetic models of depression, the Flinders Sensitive Line and Fawn Hooded rats. Maternal "deprivation" has been identified as one risk factor in the development of psychopathology, including depression in adulthood. In view of these findings we hypothesized that brain NPY may also be decreased in an animal model of early life maternal deprivation. To test this hypothesis, male and female Sprague-Dawley rats were maternally separated (MS) 6 h/day or briefly handled from postnatal day 2 (PN2) to PN6 and from PN9 to PN13. At 12 weeks of age the rats were sacrificed, the brains dissected and NPY-LI measured by radioimmunoassay. MS rats had lower NPY-LI in the hippocampus. NPY-LI was also lower in female compared to male rats in hippocampus. Lastly, NPY-LI was increased in the hypothalamus of both male and female MS rats. These findings support the hypothesis that altered NPY in the limbic region is a common denominator of several models of depression and might be a trait marker of vulnerability to affective disorders.

Neuropeptide Y in male and female brains of Flinders Sensitive Line, a rat model of depression. Effects of electroconvulsive stimuli

Human and animal studies suggest that neuropeptide Y (NPY), a peptide co-localized and co-released with classical neurotransmitters, is involved in the pathogenesis of affective disorders. In addition, lithium, electroconvulsive treatments (ECT in humans and ECS in rodents) and antidepressants affect NPY in a specific temporal- and brain-region fashion. These results have been obtained on healthy male rats; females and/or "depressed" animals have essentially not been studied. Consequently, we studied brain NPY-like immunoreactivity (-LI) under basal conditions and following a series of ECS in both male and female Flinders Sensitive Line (FSL), an animal model of depression, and their controls, the Flinders Resistant Line (FRL) rats. Furthermore, we examined whether the oestrus cycle affects NPY-LI in these strains. Following sacrifice by focused microwave irradiation, the peptides were extracted from dissected brain regions and measured by radioimmunoassay. Hippocampal NPY-LI in both sexes was significantly lower in the "depressed" FSL compared to the control FRL. ECS increased NPY-LI in both male and female rats in both FSL and FRL strains in hippocampus, frontal cortex and occipital cortex. In the hypothalamus, the increase was found only in the FSL rats. In both FSL and control rats, the basal NPY-LI was lower in the hippocampus of female compared to male rats. NPY-LI did not vary during the different phases of the oestrus cycle. These results suggest that the gender differences are not due to NPY-LI variations during the oestrus. The results are consistent with our hypothesis that NPY plays a role in the pathophysiology of depressive disorders and provide further evidence that one of the modes of ECS action is to elevate NPY in the limbic system. Assumption that gender differences in NPY could explain increased rates of depression in women is speculative, but is in line with the findings in the present study.

Neuropeptide Y in brains of the Flinders Sensitive Line rat, a model of depression. Effects of electroconvulsive stimuli and d-amphetamine on peptide concentrations and locomotion

Neuropeptide Y (NPY), has been implicated in the pathophysiology of depression and the mechanisms of action of electroconvulsive treatment (ECT). In this series of experiments, we explored whether there are differences between Flinders Sensitive Line (FSL) rats, an animal model of depression, and controls, Flinders Resistant Line (FRL) in (1) baseline brain NPY-LI concentrations, (2) effects of ECS on locomotion and brain neuropeptides, (3) amphetamine effects on behavior, and (4) effects of ECS pretreatment on subsequent effects of amphetamine on behavior. Both strains were divided into two groups, receiving eight ECS or ShamECS. Twenty-four hours after the last session, animals were habituated in activity boxes for 45 min before given d-amphetamine (1.5 mg.kg(-1), subcutaneously) or vehicle. Locomotor activity was then recorded for an additional 45 min. Twenty-four hours later, rats were sacrificed by microwave irradiation, the brains dissected into frontal cortex, occipital cortex, hippocampus, hypothalamus and striatum, and the neuropeptides extracted and measured by radioimmunoassay. No differences between FSL and FRL rats in baseline locomotor activity were found. FSL compared to FRL animals showed a significantly larger locomotion increase following saline and a significantly smaller increase following amphetamine. ECS pretreatment significantly decreased the saline effects on locomotion in the FSL and the amphetamine effects in the FRL rats. 'Baseline' NPY-like immunoreactivity (LI) concentrations were lower in the hippocampus of the 'depressed' rats. ECS increased NPY-LI in frontal cortex, occipital cortex and hippocampus of both strains. The hippocampal NPY-LI increase was significantly larger in the FSL compared to FRL animals.

Involvement of hippocampal neuropeptide Y in mediating the chronic actions of lithium, electroconvulsive stimulation and citalopram

Neuropeptide Y (NPY) has been considered to be involved in the pathogenesis of affective disorders, and chronic treatment with lithium or electroconvulsive stimuli (ECS) has been shown to increase mRNA and peptide levels of NPY in rat brain tissue. Consequently, parameters reflective of NPYergic neurotransmission were studied in the hippocampus of rats following chronic treatment with lithium, ECS or the selective serotonin re-uptake inhibitor (SSRI), citalopram. Lithium (28 days, diet) and ECS (10 days, once daily) treatments caused a marked increase in levels of preproNPY mRNA in the CA1 area and dentate gyrus (DG). This increase was accompanied by an increase in extracellular levels of NPY in the dorsal hippocampus of freely moving rats as determined by microdialysis, suggesting that lithium and ECS treatments lead to an increased biosynthesis and release of NPY in this area. (125)I-peptide YY (PYY) binding was reduced by 40 and 60% respectively in the DG following the same treatments, showing that the increased release is accompanied by a down-regulation of corresponding binding sites. In contrast, citalopram (10 mg/kg i.p., twice daily for 28 days) caused a 100% increase in (125)I-PYY binding in CA, CA3 and DG while levels of preproNPY mRNA and extracellular NPY in the hippocampus were unaffected. The results indicate that various agents and stimuli exerting antidepressant effects in humans, such as chronic lithium, ECS and citalopram all increase NPYergic neurotransmission in the hippocampus by distinct modes of action. Moreover, NPY (6 microg) given intracerebroventricularly (i.c.v.) induced an antidepressant-like effect in the forced swim test. It is hypothesised that the increase in NPYergic neurotransmission may be associated with the mechanism of action of various antidepressant treatments in the alleviation of depression.

Alterations in neuropeptide Y and Y1 receptor mRNA expression in brains from an animal model of depression: region specific adaptation after fluoxetine treatment

To investigate the possible link between neuropeptide Y (NPY) and depression, we analyzed NPY and its receptors in different limbic-related regions in the Flinder sensitive line (FSL), a genetic animal model of depression. In situ hybridization histochemistry was used to measure mRNA expression levels of NPY and NPY receptors, Y1 and Y2, in the FSL as compared to the control Flinder resistant Line rats (FRL). In the FSL rats, NPY mRNA expression levels were significantly decreased in the nucleus accumbens and CA regions, but increased in the arcuate nucleus and anterior cingulate cortex. Y1 receptor mRNA expression was decreased in different cortical regions (retrosplenial, anterior cingulate, and occipital) and in the hippocampal dentate gyrus. Y2 mRNA expression levels did not differ between FSL and FRL animals. The effect of the antidepressant drug fluoxetine (a serotonin reuptake inhibitor) in the two rat strains was also studied. There was an increase of the NPY mRNA hybridization signal in the arcuate nucleus of both strains following the antidepressant treatment (10 micromol/kg; daily for 14 days). However, in other brain regions, fluoxetine administration caused a differential effect on the induction of NPY-related genes in the two rat strains: in the CA region and dentate gyrus NPY mRNA expression was increased in the FSL, but decreased in the FRL. In contrast, Y1 mRNA levels tended to be decreased by fluoxetine in the nucleus accumbens of the FSL rats, but increased in the FRL. These findings suggest an involvement of the Y1, but not the Y2, receptor subtype in depressive disorder. Overall, the results appear to sustain the importance of the FSL rats as an animal model of depression in view of the impairment of NPY genes and the ability of fluoxetine treatment to normalize NPY-related gene expression selectively in this strain.

Neuropeptide Y, neurokinin A and neurotensin in brain regions of Fawn Hooded "depressed", Wistar, and Sprague Dawley rats. Effects of electroconvulsive stimuli

1. Concentrations of neuropeptide Y (NPY)-, neurokinin A (NKA)- and neurotensin (NT)-like immunoreactivity (-LI) were measured in brain tissues of Fawn Hooded (FH) (a model of depression), Wistar (W) (control for depression) and Sprague Dawley (SD) rats (control for strain) with the aim to explore possible associations between neuropeptides and models of depression. 2. In addition, peptides were determined after six electroconvulsive stimuli (ECS) or six sham ECS ("baseline") in order to investigate ECS mechanisms of action. 3. Baseline NPY-LI concentrations were markedly lower in the hippocampus of the "depressed" FH compared to the W and SD animals. 4. Baseline NKA-LI concentrations were higher in the occipital cortex and NT-LI concentrations in the occipital cortex, frontal cortex, and hypothalamus of the FH and W compared to the SD rats. 5. ECS increased NPY-LI in the hippocampus, frontal cortex and occipital cortex of all three strains. In the hippocampus, the increase was significantly larger in the FH compared to the W and SD rats. ECS also increased NKA-LI in the hippocampus. 6. In contrast, ECS decreased NT-LI in the occipital cortex of the FH and W animals. 7. The results indicate that NPY may play a role in depression and that changes in NPY and NKA probably constitute one of the mechanisms of ECT action. More speculatively, NT may also be involved in depression.

Concurrent analysis of neuropeptides and biogenic amines in brain tissue of rats treated with electroconvulsive stimuli

We developed a method for measuring neuropeptides and monoamines in the same rat brain tissue and applied this method to study the effects of electroconvulsive stimuli (ECS) on these compounds. Rats were treated with repeated ECS or sham ECS. After sacrifice by focused microwave irradiation, brains were dissected and immediately frozen. The tissues were extracted in acetic acid. After lyophilization the samples were reconstituted in phosphate buffer and divided in three fractions: (1) was further purified on a cation-exchange column before catecholamines were measured on a high-performance liquid chromatography (HPLC) system, (2) for measuring serotonin on the HPLC system, (3) for measuring peptide concentrations by specific radioimmunoassays. Confirming our previous findings, ECS significantly increased neuropeptide Y-like immunoreactivity (-LI) in hippocampus and frontal cortex and neurokinin A-LI in the hippocampus, while no changes in substance P- and neurotensin-LI were detected. New findings were a decrease in noradrenaline concentrations in the frontal and occipital cortex and hippocampus, an increase in dopamine concentrations in the frontal and occipital cortex and no serotonin change. In summary, we have developed methods to measure both peptides and monoamines in the same brain tissue specimens, and have shown that ECS leads to changes in both neuropeptides and classical neurotransmitters in distinct brain regions.