Animal models of depression: olfactory lesions affect amygdala, subventricular zone, and aggression

Xiangshao Granules reduce the aggressive behavior and hippocampal injury of premenstrual irritability in rats by regulating JIK/JNK/p38 signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

As a typical prescription for soothing the liver, Xiangshao granule has a good effect on the symptoms of irritability and anxiety. Clinical evidence suggests that it has significant efficacy in the treatment of Premenstrual dysphoria disorder (PMDD). However, the underlying mechanism remains unclear.

AIM OF THE STUDY

PMDD is a common disease in women of childbearing age, seriously affecting their family, society, and daily work life. The registered herbal medicine, Xiangshao granules, is used for relieving PMDD dysphoria and irritability symptoms with excellent efficacy in China. This study was focused on the deep intervention mechanism of Xiangshao granules in treating PMDD.

MATERIALS AND METHODS

The vaginal smear and open field test were used to screen rats in nonreception phase of estrus cycle with similar macroscopic behaviors and regular estrus cycle. The rat model of PMDD irritability was established through social isolation and residential invasion, with which, the irritability symptoms of PMDD patients with menstrual cycle dependence was also well simulated. Elevated plus Maze Test and Social interaction activities were used to measure the anxiety-like behavior of rats. TUNEL Staining and Hematoxylin-Eosin staining were used to measure apoptosis of hippocampal neurons. RT-PCR, Western blot and immunofluorescence were used to measure the expression of GR, JIK, p-JIK, p38, P-P38, JNK, caspase 3, and caspase 12.

RESULTS

In this study, Xiangshao granules showed consistent therapeutic effects similar with those in clinic, significantly reducing aggressive and anxiety-like behaviors with improved social skills in PMDD rats. In mechanism, Xiangshao granules lowered the apoptosis of hippocampal neurons and weakened the morphological damage of the hippocampal brain evidenced by the decreased mRNA and protein expression of glucocorticoid receptor, caspase-3, and caspase-12. In addition, administration of Xiangshao granules led to the decreased expression of JIK in the PMDD irritability rat model which agreed well with the previous studies. The JNK/p38 mitogen-activated protein kinases (MAPKs) signaling pathway is abnormally activated in the hippocampal brain region of PMDD rats, while treated with Xiangshao granules could increase JIK expression and inhibit the abnormal activation of the JNK/p38 MAPK signaling pathway, effectively reducing the stress damage in the hippocampus.

CONCLUSIONS

Xiangshao Granules Reduce the Aggressive Behavior and Hippocampal Injury of Premenstrual Irritability in Rats by Regulating JIK/JNK/p38 Signal Pathway.

GABABR1 in DRN mediated GABA to regulate 5-HT expression in multiple brain regions in male rats with high and low aggressive behavior

The identity of the mechanism that controls aggressive behavior in rodents is unclear. Serotonin (5-HT) and GABA are associated with aggressive behavior in rodents. However, the regulatory relationship between these chemicals in the different brain regions of rats has not been fully defined. This study aimed to clarify the role of GABABR1 in DRN-mediated GABA to regulate 5-HT expression in multiple brain regions in male rats with high and low aggressive behavior. Rat models of highly and less aggressive behavior were established through social isolation plus resident intruder. On this basis, GABA content in the DRN and 5-HT contents in the PFC, hypothalamus, hippocampus and DRN were detected using ELISA. Co-expression of 5-HT and GB1 in the DRN was detected by immunofluorescence and immunoelectron microscopy at the tissue and subcellular levels, respectively. GB1-specific agonist baclofen and GB1-specific inhibitor CGP35348 were injected into the DRN by stereotaxic injection. Changes in 5-HT levels in the PFC, hypothalamus and hippocampus were detected afterward. After modeling, rats with highly aggressive behavior exhibited higher aggressive behavior scores, shorter latencies of aggression, and higher total distances in the open field test than rats with less aggressive behavior. The contents of 5-HT in the PFC, hypothalamus and hippocampus of rats with high and low aggressive behavior (no difference between the two groups) were significantly decreased, but the change in GABA content in the DRN was the opposite. GB1 granules could be found on synaptic membranes containing 5-HT granules, which indicated that 5-HT neurons in the DRN co-expressed with GB1, which also occurred in double immunofluorescence results. At the same time, we found that the expression of GB1 in the DRN of rats with high and low aggressive behavior was significantly increased, and the expression of GB1 in the DRN of rats with low aggressive behavior was significantly higher than that in rats with high aggressive behavior. Nevertheless, the expression of 5-HT in DRN was opposite in these two groups. After microinjection of baclofen into the DRN, the 5-HT contents in the PFC, hypothalamus and hippocampus of rats in each group decreased significantly. In contrast, the 5-HT contents in the PFC, hypothalamus and hippocampus of rats in each group increased significantly after injection with CGP35348. The significant increase in GABA in the DRN combined with the significant increase in GB1 in the DRN further mediated the synaptic inhibition effect, which reduced the 5-HT level of 5-HT neurons in the DRN, resulting in a significant decrease in 5-HT levels in the PFC, hypothalamus and hippocampus. Therefore, GB1-mediated GABA regulation of 5-HT levels in the PFC, hypothalamus and hippocampus is one of the mechanisms of highly and less aggressive behavior originating in the DRN. The increased GB1 level in the DRN of LA-behavior rats exhibited a greater degree of change than in the HA-group rats, which indicated that differently decreased 5-HT levels in the DRN may be the internal mechanisms of high and low aggression behaviors.

The olfactory bulbectomy disease model: A Re-evaluation

The olfactory bulbectomized rodent has long been one of the preferred animal models of depression and certain other neuropsychiatric diseases. In fact, it is considered unparalleled, by some, in the search for antidepressant medication and the literature generated about the model is prodigious. We have revisited the "syndrome" of behavioral sequela following bulbectomy choosing ecologically valid tests likely to be underpinned with evolutionarily preserved neural circuits. Our test battery included measurements of activity, intermale aggression, pleasure seeking, stress/fear and non-spatial memory. The emphasis was on the timetable of syndrome emergence, since this has been understudied and bears on the widely held belief that non-olfactory effects dominate. Our results largely agree with previous reports describing the behavioral syndrome in that we document bulbectomized mice as hyperactive, non-aggressive and fearless. However, we did not find deficits in memory as have frequently been reported in previous studies. Notably, our results revealed that some syndrome behaviors-including the hallmark of hyperactivity-appear immediately or soon after surgery. This rapid appearance casts doubt on the widely held view that compensatory reorganization of limbic and prefrontal cortical areas following bulbectomy underlies the syndrome. Rather, hyperactivity, non-aggressiveness, reduced fear and diminished sucrose preference in the olfactory bulbectomized mouse find ready explanations in the loss of smell that is the immediate and irreversible outcome of bulbectomy. Finally, after a critical consideration of the literature and our results, we conclude that the olfactory bulbectomy model lacks the validity and simplicity previously credited to it. Indeed, we deem this lesion unsuitable as a model of most neuropsychiatric diseases since its effects are at least as complex and misunderstood as the disorders it is purported to model.

MT2 melatonin receptors expressed in the olfactory bulb modulate depressive-like behavior and olfaction in the 6-OHDA model of Parkinson's disease

Melatonin MT1 and MT2 receptors are expressed in the glomerular layer of the olfactory bulb (OB); however, the role of these receptors has not been evaluated until now. Considering the association of the OB with olfactory and depressive disorders in Parkinson's disease (PD), we sought to investigate the involvement of melatonin receptors in these non-motor disturbances in an intranigral 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD. We demonstrate the presence of functional melatonin receptors in dopaminergic neurons of the glomerular layer. Local administration of melatonin (MLT, 1 μg/μl), luzindole (LUZ, 5 μg/μl) or the MT2-selective receptor drug 4-P-PDOT (5 μg/μl) reversed the depressive-like behavior elicited by 6-OHDA. Sequential administration of 4-P-PDOT and MLT (5 μg/μl, 1 μg/μl) promoted additive antidepressant-like effects. In the evaluation of olfactory discrimination, LUZ induced an olfactory impairment when associated with the nigral lesion-induced impairment. Thus, our results suggest that melatonin MT2 receptors expressed in the glomerular layer are involved in depressive-like behaviors and in olfactory function associated with PD.

Protein Kinase A Catalytic and Regulatory Subunits Interact Differently in Various Areas of Mouse Brain

Protein kinase A (PKA) are tetramers of two catalytic and two regulatory subunits, docked at precise intracellular sites to provide localized phosphorylating activity, triggered by cAMP binding to regulatory subunits and subsequent dissociation of catalytic subunits. It is unclear whether in the brain PKA dissociated subunits may also be found. PKA catalytic subunit was examined in various mouse brain areas using immunofluorescence, equilibrium binding and western blot, to reveal its location in comparison to regulatory subunits type RI and RII. In the cerebral cortex, catalytic subunits colocalized with clusters of RI, yet not all RI clusters were bound to catalytic subunits. In stria terminalis, catalytic subunits were in proximity to RI but separated from them. Catalytic subunits clusters were also present in the corpus striatum, where RII clusters were detected, whereas RI clusters were absent. Upon cAMP addition, the distribution of regulatory subunits did not change, while catalytic subunits were completely released from regulatory subunits. Unpredictably, catalytic subunits were not solubilized; instead, they re-targeted to other binding sites within the tissue, suggesting local macromolecular reorganization. Hence, the interactions between catalytic and regulatory subunits of protein kinase A consistently vary in different brain areas, supporting the idea of multiple interaction patterns.

The Neurobiology of Mixed States

Interest in the coexistence of manic and depressive symptoms fostered hypotheses on neurobiological underpinnings of mixed states. Neurobiological properties of mixed states, however, have not been comprehensively described. The authors searched databases for articles on neurobiological markers related to mixed states. Results showed that mixed states are characterized by elevated central and peripheral monoamine levels, greater alterations in hypothalamic-pituitary-adrenal axis, increased inflammation, and greater circadian rhythms dysfunction than nonmixed forms. Furthermore, the magnitude of pathophysiologic alterations in mixed states exceeds those associated with nonmixed mania or depression and suggest that hyperactivation and hyperarousal are core features of mixed states.

A new sensitive and subunit-selective molecular tool for investigating protein kinase A in the brain

Despite cellular complexity, a limited number of small molecules act as intracellular second messengers. Protein kinase A (PKA) is the main transducer of the information carried by cyclic adenosine monophosphate (cAMP). Recently, cellular imaging has achieved major technical advancements, although the search for more specific and sensitive low-molecular-weight probes to explore subcellular events involving second messengers is still in progress. The convergent synthesis of a novel, fluorescent small molecule comprising the cAMP structure and a rhodamine-based fluorescent residue, connected through a flexible linker, is described here. The interaction motif of this compound with PKA was investigated in silico using a blind docking approach, comparing its theoretical binding energy with the one calculated for cAMP. Moreover, the predicted pharmacokinetic properties were also computed and discussed. The new probe was tested on three areas of the mouse central nervous system (parietal cerebral cortex, hippocampus, and cerebellar cortex) with different fixation methods demonstrating remarkable selectivity towards the PKA RIα subunit. The probe showed overall better performances when compared to other commercially available fluorescent cAMP analogues, acting at lower concentrations, and providing stable labeling.

Protein Kinase A Distribution in Meningioma

Deregulation of intracellular signal transduction pathways is a hallmark of cancer cells, clearly differentiating them from healthy cells. Differential intracellular distribution of the cAMP-dependent protein kinases (PKA) was previously detected in cell cultures and in vivo in glioblastoma and medulloblastoma. Our goal is to extend this observation to meningioma, to explore possible differences among tumors of different origins and prospective outcomes. The distribution of regulatory and catalytic subunits of PKA has been examined in tissue specimens obtained during surgery from meningioma patients. PKA RI subunit appeared more evenly distributed throughout the cytoplasm, but it was clearly detectable only in some tumors. RII was present in discrete spots, presumably at high local concentration; these aggregates could also be visualized under equilibrium binding conditions with fluorescent 8-substituted cAMP analogues, at variance with normal brain tissue and other brain tumors. The PKA catalytic subunit showed exactly overlapping pattern to RII and in fixed sections could be visualized by fluorescent cAMP analogues. Gene expression analysis showed that the PKA catalytic subunit revealed a significant correlation pattern with genes involved in meningioma. Hence, meningioma patients show a distinctive distribution pattern of PKA regulatory and catalytic subunits, different from glioblastoma, medulloblastoma, and healthy brain tissue. These observations raise the possibility of exploiting the PKA intracellular pathway as a diagnostic tool and possible therapeutic interventions.

Animal models of major depressive disorder and the implications for drug discovery and development

INTRODUCTION

Depression is a highly debilitating psychiatric disorder that affects the global population and causes severe disabilities and suicide. Depression pathogenesis remains poorly understood, and the disorder is often treatment-resistant and recurrent, necessitating the development of novel therapies, models and concepts in this field. Areas covered: Animal models are indispensable for translational biological psychiatry, and markedly advance the study of depression. Novel approaches continuously emerge that may help untangle the disorder heterogeneity and unclear categories of disease classification systems. Some of these approaches include widening the spectrum of model species used for translational research, using a broader range of test paradigms, exploring new pathogenic pathways and biomarkers, and focusing more closely on processes beyond neural cells (e.g. glial, inflammatory and metabolic deficits). Expert opinion: Dividing the core symptoms into easily translatable, evolutionarily conserved phenotypes is an effective way to reevaluate current depression modeling. Conceptually novel approaches based on the endophenotype paradigm, cross-species trait genetics and 'domain interplay concept', as well as using a wider spectrum of model organisms and target systems will enhance experimental modeling of depression and antidepressant drug discovery.

Medium- and high-intensity rTMS reduces psychomotor agitation with distinct neurobiologic mechanisms

Definitive data are lacking on the mechanism of action and biomarkers of repetitive transcranial magnetic stimulation (rTMS) for the treatment of depression. Low-intensity rTMS (LI-rTMS) has demonstrated utility in preclinical models of rTMS treatments but the effects of LI-rTMS in murine models of depression are unknown. We examined the behavioral and neurobiologic changes in olfactory bulbectomy (OB) mice with medium-intensity rTMS (MI-rTMS) treatment and fluoxetine hydrochloride. We then compared 10-Hz rTMS sessions for 3 min at intensities (measured at the cortical surface) of 4 mT (LI-rTMS), 50 mT (medium-intensity rTMS [MI-rTMS]), or 1 T (high-intensity rTMS [HI-rTMS]) 5 days per week over 4 weeks in an OB model of agitated depression. Behavioral effects were assessed with forced swim test; neurobiologic effects were assessed with brain levels of 5-hydroxytryptamine, brain-derived neurotrophic factor (BDNF), and neurogenesis. Peripheral metabolomic changes induced by OB and rTMS were monitored through enzyme-linked immunosorbent assay and ultrapressure liquid chromatography-driven targeted metabolomics evaluated with ingenuity pathway analysis (IPA). MI-rTMS and HI-rTMS attenuated psychomotor agitation but only MI-rTMS increased BDNF and neurogenesis levels. HI-rTMS normalized the plasma concentration of α-amino-n-butyric acid and 3-methylhistidine. IPA revealed significant changes in glutamine processing and glutamate signaling in the OB model and following MI-rTMS and HI-rTMS treatment. The present findings suggest that MI-rTMS and HI-rTMS induce differential neurobiologic changes in a mouse model of agitated depression. Further, α-amino-n-butyric acid and 3-methylhistidine may have utility as biomarkers to objectively monitor the response to rTMS treatment of depression.

Drug-induced Parkinson's disease modulates protein kinase A and Olfactory Marker Protein in the mouse olfactory bulb

Background

Olfaction is often affected in parkinsonian patients, but dopaminergic cells in the olfactory bulb are not affected by some Parkinson-inducing drugs. We investigated whether the drug MPTP produces the olfactory deficits typical of Parkinson and affects the olfactory bulb in mice.

Findings

Lesioned and control mice were tested for olfactory search, for motor and exploratory behavior. Brains and olfactory mucosa were investigated via immunohistochemistry for thyrosine hydroxylase, Olfactory Marker Protein and cyclic AMP-dependent protein kinase as an intracellular pathway involved in dopaminergic neurotransmission. MPTP induced motor impairment, but no deficit in olfactory search. Thyrosine hydroxylase did not differ in olfactory bulb, while a strong decrease was detected in substantia nigra and tegmentum of MPTP mice. Olfactory Marker Protein decreased in the olfactory bulb of MPTP mice, while a cyclic AMP-dependent protein kinase increased in the inner granular layer of MPTP mice.

Conclusions

MPTP mice do not present behavioural deficits in olfactory search, yet immunoreactivity reveals modifications in the olfactory bulb, and suggests changes in intracellular signal processing, possibly linked to neuron survival after MPTP.

Rapamycin blocks the antidepressant effect of ketamine in task-dependent manner

OBJECTIVE

The aim of our study was to test whether ketamine produces an antidepressant effect in animal model of olfactory bulbectomy and assess the role of mammalian target of rapamycin (mTOR) pathway in ketamine's antidepressant effect.

METHODS

Bulbectomized (OBX) rats and sham controls were assigned to four subgroups according to the treatment they received (ketamine, saline, ketamine + rapamycin, and saline + rapamycin). The animals were subjected to open field (OF), elevated plus maze (EPM), passive avoidance (PA), Morris water maze (MWM), and Carousel maze (CM) tests. Blood samples were collected before and after drug administration for analysis of phosphorylated mTOR level. After behavioral testing, brains were removed for evaluation of brain-derived neurotrophic factor (BDNF) in prefrontal cortex (PFC) and hippocampus.

RESULTS

Ketamine normalized hyperactivity of OBX animals in EPM and increased the time spent in open arms. Rapamycin pretreatment resulted in elimination of ketamine effect in EPM test. In CM test, ketamine + rapamycin administration led to cognitive impairment not observed in saline-, ketamine-, or saline + rapamycin-treated OBX rats. Prefrontal BDNF content was significantly decreased, and level of mTOR was significantly elevated in OBX groups.

CONCLUSIONS

OBX animals significantly differed from sham controls in most of the tests used. Treatment had more profound effect on OBX phenotype than controls. Pretreatment with rapamycin eliminated the anxiolytic and antidepressant effects of ketamine in task-dependent manner. The results indicate that ketamine + rapamycin application resulted in impaired stress responses manifested by cognitive deficits in active place avoidance (CM) test. Intensity of stressor (mild vs. severe) used in the behavioral tests had opposite effect on controls and on OBX animals.

Serotonin and noradrenaline reuptake inhibitors improve micturition control in mice

Poor micturition control may cause profound distress, because proper voiding is mandatory for an active social life. Micturition results from the subtle interplay of central and peripheral components. It involves the coordination of autonomic and neuromuscular activity at the brainstem level, under the executive control of the prefrontal cortex. We tested the hypothesis that administration of molecules acting as reuptake inhibitors of serotonin, noradrenaline or both may exert a strong effect on the control of urine release, in a mouse model of overactive bladder. Mice were injected with cyclophosphamide (40 mg/kg), to increase micturition acts. Mice were then given one of four molecules: the serotonin reuptake inhibitor imipramine, its metabolite desipramine that acts on noradrenaline reuptake, the serotonin and noradrenaline reuptake inhibitor duloxetine or its active metabolite 4-hydroxy-duloxetine. Cyclophosphamide increased urine release without inducing overt toxicity or inflammation, except for increase in urothelium thickness. All the antidepressants were able to decrease the cyclophosphamide effects, as apparent from longer latency to the first micturition act, decreased number of urine spots and volume of released urine. These results suggest that serotonin and noradrenaline reuptake inhibitors exert a strong and effective modulatory effect on the control of urine release and prompt to additional studies on their central effects on brain areas involved in the social and behavioral control of micturition.

Anterior olfactory organ removal produces anxiety-like behavior and increases spontaneous neuronal firing rate in basal amygdala

Some chemical cues may produce signs of anxiety and fear mediated by amygdala nuclei, but unknown is the role of two anterior olfactory epithelial organs, the septal and vomeronasal organs (SO-VNOs). The effects of SO-VNO removal were explored in different groups of Wistar rats using two complementary approaches: (i) the assessment of neuronal firing rate in basal and medial amygdala nuclei and (ii) behavioral testing. Fourteen days after SO-VNO removal, spontaneous activity in basal and medial amygdala nuclei in one group was determined using single-unit extracellular recordings. A separate group of rats was tested in the elevated plus maze, social interaction test, and open field test. Compared with sham-operated and intact control rats, SO-VNO removal produced a higher neuronal firing rate in the basal amygdala but not medial amygdala. In the behavioral tests, SO-VNO removal increased signs of anxiety in the elevated plus maze, did not alter locomotion, and increased self-directed behavior, reflecting anxiety-like behavior. Histological analysis showed neuronal destruction in the accessory olfactory bulb but not anterior olfactory nucleus in the SO-VNO group. The present results suggest the participation of SO-VNO/accessory olfactory bulb/basal amygdala relationships in the regulation of anxiety through a process of disinhibition.

Effects of a copper-deficient diet on the biochemistry, neural morphology and behavior of aged mice

Copper dyshomeostasis has been suggested as an aetiological risk factor for some neurodegenerative diseases, such as Alzheimer’s disease. However, the precise mechanism at the base of this involvement is still obscure. In this work, we show the effects of a copper-deficient diet in aged CD1 mice and the influence of such a diet on: a) the concentration of various metal ions (aluminium, copper, iron, calcium, zinc) in the main organs and in different brain areas; b) the alteration of metallothioneins I-II and tyrosine hydroxylase immunopositivity in the brain; c) behavioural tests (open field, pole, predatory aggression, and habituation/dishabituation smell tests). Our data suggested that the copper-deficiency was able to produce a sort of “domino effect” which altered the concentration of the other tested metal ions in the main organs as well as in the brain, without, however, significantly affecting the animal behaviour.

Protein kinase a in cancer

In the past, many chromosomal and genetic alterations have been examined as possible causes of cancer. However, some tumors do not display a clear molecular and/or genetic signature. Therefore, other cellular processes may be involved in carcinogenesis. Genetic alterations of proteins involved in signal transduction have been extensively studied, for example oncogenes, while modifications in intracellular compartmentalization of these molecules, or changes in the expression of unmodified genes have received less attention. Yet, epigenetic modulation of second messenger systems can deeply modify cellular functioning and in the end may cause instability of many processes, including cell mitosis. It is important to understand the functional meaning of modifications in second messenger intracellular pathways and unravel the role of downstream proteins in the initiation and growth of tumors. Within this framework, the cAMP system has been examined. cAMP is a second messenger involved in regulation of a variety of cellular functions. It acts mainly through its binding to cAMP-activated protein kinases (PKA), that were suggested to participate in the onset and progression of various tumors. PKA may represent a biomarker for tumor detection, identification and staging, and may be a potential target for pharmacological treatment of tumors.

Dietary restriction mitigates cocaine-induced alterations of olfactory bulb cellular plasticity and gene expression, and behavior

Because the olfactory system plays a major role in food consumption, and because 'food addiction' and associated morbidities have reached epidemic proportions, we tested the hypothesis that dietary energy restriction can modify adverse effects of cocaine on behavior and olfactory cellular and molecular plasticity. Mice maintained on an alternate day fasting (ADF) diet exhibited increased baseline locomotion and increased cocaine-sensitized locomotion during cocaine conditioning, despite no change in cocaine conditioned place preference, compared with mice fed ad libitum. Levels of dopamine and its metabolites in the olfactory bulb (OB) were suppressed in mice on the ADF diet compared with mice on the control diet, independent of acute or chronic cocaine treatment. The expression of several enzymes involved in dopamine metabolism including tyrosine hydroxylase, monoamine oxidases A and B, and catechol-O-methyltransferase were significantly reduced in OBs of mice on the ADF diet. Both acute and chronic administration of cocaine suppressed the production of new OB cells, and this effect of cocaine was attenuated in mice on the ADF diet. Cocaine administration to mice on the control diet resulted in up-regulation of OB genes involved in mitochondrial energy metabolism, synaptic plasticity, cellular stress responses, and calcium- and cAMP-mediated signaling, whereas multiple olfactory receptor genes were down-regulated by cocaine treatment. ADF abolished many of the effects of cocaine on OB gene expression. Our findings reveal that dietary energy intake modifies the neural substrates underlying some of the behavioral and physiological responses to repeated cocaine treatment, and also suggest novel roles for the olfactory system in addiction. The data further suggest that modification of dietary energy intake could provide a novel potential approach to addiction treatments.

The olfactory system is affected by steroid aerosol treatment in mice

Asthma needs continuous treatment often for years. In humans, some drugs are administered via aerosol, therefore they come in contact with both respiratory and olfactory mucosa. We explored the possibility that antiasthma corticosteroid treatment could influence the olfactory function by passage through the nose. A group of mice was exposed twice daily for 42 days to fluticasone propionate aerosol and was compared with a control group. Olfactory behavior, respiratory mechanics, histology, and immunoreactivity in the olfactory system were assessed. Fluticasone-treated mice were slower in retrieving a piece of hidden food, but both groups were similarly fast when the food was visible. When a clearly detectable odor was present in the environment, all mice behaved in a similar way. Respiratory mechanics indices were similar in all mice except for the viscose resistance, which was reduced in fluticasone-treated mice. Olfactory mucosa of fluticasone-treated mice was thicker than that of controls. Slight but consistent differences in staining were present for Olfactory Marker Protein but not for other proteins. A mild impairment of olfactory function is present in mice chronically treated with fluticasone aerosol, apparently accompanied by slight modifications of the olfactory receptor cells, and suggests monitoring of olfactory function modifications in long-term steroid users.

Chronic fluoxetine treatment attenuates stressor-induced changes in temperature, heart rate, and neuronal activation in the olfactory bulbectomized rat

The olfactory bulbectomized (OB) rat is a well-characterized animal model that exhibits a number of behavioral and neurochemical changes that have relevance to clinical depression. Hyperactivity in the open field is the most widely used parameter assessed in this model and is reversed following chronic, but not acute, antidepressant treatment. This study investigated OB-induced alterations in heart rate, body temperature, and neuronal activation following open-field exposure and the impact of chronic treatment with fluoxetine on these parameters. Upon placement in the open field, OB rats exhibited a characteristic hyperactivity response. Heart rate and body temperature were increased in sham-operated rats following open-field exposure, a predictable response to stress, which was significantly reduced in OB rats. Moreover bulbectomy reduced open field-induced cFOS expression in the basal nucleus of the stria terminalis while concurrently increasing expression in the hippocampus, amygdala, paraventricular nucleus of the thalamus, and dorsal raphe nucleus. Chronic fluoxetine treatment (10 mg/kg subcutaneous once daily for 5 weeks) attenuated all of these OB-associated changes. In conclusion, OB rats exhibit alterations in behavior, body temperature, heart rate, and neuronal activation in response to open-field exposure, which are reversed following chronic fluoxetine administration. These results identify stress-sensitive regions within the brain which are altered following bulbectomy and which may underlie the abnormal behavioral and physiological changes observed in this rodent model of depression.

5-HT7, NEUROGENESIS AND ANTIDEPRESSANTS: A PROMISING THERAPEUTIC AXIS FOR TREATING DEPRESSION

1. There is mounting evidence that a wide range of antidepressants share the common feature of increasing hippocampal neurogenesis. The specificity of this association has suggested that an ability to increase neurogenesis might be a useful paradigm to screen for compounds with antidepressant activity. 2. The hope of developing better antidepressants has stimulated research into the molecular control of neurogenesis and here we summarize some of the recent findings. We also review recent work that highlights 5-HT7 receptor as a promising molecular target in the treatment of depression. 3. In summary, it appears that 5-HT7 antagonism is capable of producing diverse antidepressant-like behavioural effects, alters hippocampal neuronal morphology and synergistically regulates hippocampal neurogenesis.

The critical role of familiar urine odor in diminishing territorial aggression toward a castrated intruder in mice

Sensory chemo-signals conveying information on sex and familiarity are important to the manifestation of aggressive behaviors in male mice. In this study, we examined the role of familiarity conveyed by urine odor in the induction of aggressive behavior using a resident-intruder paradigm. First, an intact ICR male mouse (resident) was grouped with a castrated DBA mouse (cage-mate) and a female ICR mouse to allow the resident mouse to establish its territory. The resident male showed vigorous aggression, not only toward intact male DBA intruders, but also toward unfamiliar castrated DBA mice (UFC). In contrast, the aggression was markedly reduced toward its castrated DBA cage-mate. Next, to reveal how residents discriminate their cage-mates from unfamiliar intruders, we examined whether urine odor affected this familiarity-related aggression. When part of the body surface of a UFC was swabbed with the urine of a resident's cage-mate, the resident attacked the UFC much less often. These results suggest that the information about familiarity conveyed by urine odor plays an important role in controlling the territorial aggression of a resident male mouse toward castrated intruders.

Region-specific transcriptional changes following the three antidepressant treatments electro convulsive therapy, sleep deprivation and fluoxetine

The significant proportion of depressed patients that are resistant to monoaminergic drug therapy and the slow onset of therapeutic effects of the selective serotonin reuptake inhibitors (SSRIs)/serotonin/noradrenaline reuptake inhibitors (SNRIs) are two major reasons for the sustained search for new antidepressants. In an attempt to identify common underlying mechanisms for fast- and slow-acting antidepressant modalities, we have examined the transcriptional changes in seven different brain regions of the rat brain induced by three clinically effective antidepressant treatments: electro convulsive therapy (ECT), sleep deprivation (SD), and fluoxetine (FLX), the most commonly used slow-onset antidepressant. Each of these antidepressant treatments was applied with the same regimen known to have clinical efficacy: 2 days of ECT (four sessions per day), 24 h of SD, and 14 days of daily treatment of FLX, respectively. Transcriptional changes were evaluated on RNA extracted from seven different brain regions using the Affymetrix rat genome microarray 230 2.0. The gene chip data were validated using in situ hybridization or autoradiography for selected genes. The major findings of the study are: 1. The transcriptional changes induced by SD, ECT and SSRI display a regionally specific distribution distinct to each treatment. 2. The fast-onset, short-lived antidepressant treatments ECT and SD evoked transcriptional changes primarily in the catecholaminergic system, whereas the slow-onset antidepressant FLX treatment evoked transcriptional changes in the serotonergic system. 3. ECT and SD affect in a similar manner the same brain regions, primarily the locus coeruleus, whereas the effects of FLX were primarily in the dorsal raphe and hypothalamus, suggesting that both different regions and pathways account for fast onset but short lasting effects as compared to slow-onset but long-lasting effects. However, the similarity between effects of ECT and SD is somewhat confounded by the fact that the two treatments appear to regulate a number of transcripts in an opposite manner. 4. Multiple transcripts (e.g. brain-derived neurotrophic factor (BDNF), serum/glucocorticoid-regulated kinase (Sgk1)), whose level was reported to be affected by antidepressants or behavioral manipulations, were also found to be regulated by the treatments used in the present study. Several novel findings of transcriptional regulation upon one, two or all three treatments were made, for the latter we highlight homer, erg2, HSP27, the proto oncogene ret, sulfotransferase family 1A (Sult1a1), glycerol 3-phosphate dehydrogenase (GPD3), the orphan receptor G protein-coupled receptor 88 (GPR88) and a large number of expressed sequence tags (ESTs). 5. Transcripts encoding proteins involved in synaptic plasticity in the hippocampus were strongly affected by ECT and SD, but not by FLX. The novel transcripts, concomitantly regulated by several antidepressant treatments, may represent novel targets for fast onset, long-duration antidepressants.

Low inborn anxiety correlates with high intermale aggression: link to ACTH response and neuronal activation of the hypothalamic paraventricular nucleus

Aggression constitutes a central problem in several psychopathologies, including anxiety and depression disorders and antisocial behaviors. In particular, the activity of the hypothalamic-pituitary-adrenocortical (HPA) axis has been associated with aggression-related disorders. The present study assessed whether genetically determined levels of anxiety-related behavior influence the level of intermale aggression and whether this is associated with differences in neuroendocrine responsiveness and neuronal activation in the brain. Adult male Wistar rats bred for high (HAB) or low (LAB) anxiety-related behavior were used, as well as non-selected rats (NAB) with an intermediate anxiety level. LAB residents displayed more aggressive behavior than HAB and NAB residents during the resident-intruder (RI) test. Moreover, an inverse correlation was found between the level of anxiety and the level of aggression. The plasma corticotropin (ACTH) response to RI-test exposure was significantly higher in LABs than in HABs and NABs, indicating that a higher level of aggression was linked to an elevated hormonal stress response. Furthermore, LAB residents showed more neuronal activation in the parvocellular part of the hypothalamic paraventricular nucleus (PVN) than HAB residents 1 h after the RI-test. In addition, a tendency toward a higher number of c-Fos-positive cells in LABs compared with HABs was observed in the medial amygdala, hypothalamic attack area and central amygdala, areas relevant for the regulation of aggression. These data demonstrate that low trait anxiety is correlated with high intermale aggression. Furthermore, the increased neuronal activation of the PVN along with the higher ACTH responsiveness might underlie the display of high aggression.

Olfactory bulbectomy in mice leads to increased BDNF levels and decreased serotonin turnover in depression-related brain areas

The olfactory bulbectomy in rodents has been proposed as an animal model for depression. According to the neurotrophin and monoamine hypotheses of depression, the present study examined neurotrophin and monoamine (serotonin, norepinephrine, dopamine) levels in several depression-related brain regions of mice subjected to olfactory bulbectomy. As expected, bulbectomized animals revealed behavioral alterations such as locomotor hyperactivity and reduced gain of bodyweight, regarded as correlates of a depressive-like state. Compared to sham-operated animals, bulbectomized mice demonstrated significantly increased brain-derived neurotrophic factor (BDNF), but regular nerve growth factor (NGF), protein levels in hippocampus (+108%) and frontal cortex (+48%) 16 days after olfactory bulbectomy. In these brain regions as well as in the hypothalamus, bulbectomy also caused a reduction of the molar ratio of 5-hydroxyindoleacetic acid to serotonin (5-HT) indicating a decrease in 5-HT turnover. Similarly, a hypofunction of the dopamine (DA) turnover was evident only in the hypothalamus in response to olfactory bulbectomy, presenting a decrease in the ratio 3,4 dihydroxyphenylacetic acid/DA with increased levels of DA. In all other brain areas investigated the levels of DA, its metabolite DOPAC and norepinephrine remained unaltered. Thus, olfactory bulbectomy seems to be a valid animal model also in mice related to serotonergic dysfunctions resembling bulbectomized rats that are a well-known model of hyposerotoninergic agitated depression. With respect to the common BDNF hypothesis of depression--predicting decreased BDNF expression in depression-related brain areas--the novel and challenging conclusions concern the increased BDNF protein levels in target regions of the cholinergic basal forebrain system in bulbectomized mice.

Time course of alterations after olfactory bulbectomy in mice

Olfactory bulbectomy in rodents causes behavioral alterations, which result in a model of depression, validated for pharmacological screening of antidepressant drugs. To unravel the appearance and time course of the major behavioral effects which follow surgery, mice underwent olfactory bulb ablation or sham operation, and were analyzed after 1, 2, or 4 weeks. Bulbectomized (BX) mice were anosmic, and hyperactive when tested under stressful situations in the forced swimming test. Predatory aggression was upregulated in a time-dependent way: only after 4 weeks BX mice were faster than controls in attacking prey. At the same time, they were less aggressive against intruders; they did not differ from controls in open field exploration, but displayed a cognitive impairment in water maze. Behavioral tests thus indicated a marked hyperreactivity, a dissociation among different aggressive behaviors, and also a cognitive impairment induced by bulbectomy. Histological confirmation of the damage revealed that major modifications took place in the rostral pole of frontal lobes, with a significant increase in the width of the rostral migratory stream, 2 weeks after surgery, and in the subventricular zone, 4 weeks after surgery. These results suggest a base for the time-course of appearance of behavioral symptoms in BX mice.