The lateral hypothalamus and anterior hypothalamic nucleus differentially contribute to rats' defensive responses in the elevated plus-maze and shock-probe burying tests

Control of defensive behavior by the nucleus of Darkschewitsch GABAergic neurons

The nucleus of Darkschewitsch (ND), mainly composed of GABAergic neurons, is widely recognized as a component of the eye-movement controlling system. However, the functional contribution of ND GABAergic neurons (NDGABA) in animal behavior is largely unknown. Here, we show that NDGABA neurons were selectively activated by different types of fear stimuli, such as predator odor and foot shock. Optogenetic and chemogenetic manipulations revealed that NDGABA neurons mediate freezing behavior. Moreover, using circuit-based optogenetic and neuroanatomical tracing methods, we identified an excitatory pathway from the lateral periaqueductal gray (lPAG) to the ND that induces freezing by exciting ND inhibitory outputs to the motor-related gigantocellular reticular nucleus, ventral part (GiV). Together, these findings indicate the NDGABA population as a novel hub for controlling defensive response by relaying fearful information from the lPAG to GiV, a mechanism critical for understanding how the freezing behavior is encoded in the mammalian brain.

The cognitive (lateral) hypothalamus

Despite the physiological complexity of the hypothalamus, its role is typically restricted to initiation or cessation of innate behaviors. For example, theories of lateral hypothalamus argue that it is a switch to turn feeding 'on' and 'off' as dictated by higher-order structures that render when feeding is appropriate. However, recent data demonstrate that the lateral hypothalamus is critical for learning about food-related cues. Furthermore, the lateral hypothalamus opposes learning about information that is neutral or distal to food. This reveals the lateral hypothalamus as a unique arbitrator of learning capable of shifting behavior toward or away from important events. This has relevance for disorders characterized by changes in this balance, including addiction and schizophrenia. Generally, this suggests that hypothalamic function is more complex than increasing or decreasing innate behaviors.

Role of CRF1 and CRF2 receptors in the lateral hypothalamus in cardiovascular and anxiogenic responses evoked by restraint stress in rats: Evaluation of acute and chronic exposure

We investigated the role of corticotropin-releasing factor (CRF) neurotransmission within the lateral hypothalamus (LH) in cardiovascular and anxiogenic-like responses evoked by acute and repeated restraint stress in rats. For this, animals were subjected to intra-LH microinjection of a selective CRF₁ (CP376395) or CRF₂ (antisauvagine-30) receptor antagonist before either an acute or the 10th session of restraint stress. Restraint-evoked arterial pressure and heart rate increases, tail skin temperature decrease and anxiogenic-like effect in the elevated plus maze (EPM) were evaluated. We also assessed the effect of 10 daily sessions of restraint on expression of CRF₁ and CRF₂ receptors within the LH. We identified that antagonism of either CRF₁ or CRF₂ receptor within the LH decreased the tachycardia during both the acute and 10th session of restraint, but the effect of the CRF₁ receptor antagonist was more pronounced during the 10th session. Acute restraint stress also caused anxiogenic-like effect, and this response was inhibited in animals treated with either CP376395 or antisauvagine-30. Anxiety-like behaviors were not changed following the 10th session of restraint, and pharmacological treatments did not affect the behavior in the EPM in chronically stressed animals. Repeated restraint also did not change the level of the CRF receptors within the LH. Taken together, the findings indicate that CRF₁ and CRF₂ receptors within the LH are involved in tachycardic and anxiogenic-like responses to aversive stimuli. Control of tachycardia by the CRF₁ receptor is sensitized by previous stressful experience, and this effect seems to be independent of changes in expression of the receptor.

Lateral hypothalamic galanin neurons are activated by stress and blunt anxiety-like behavior in mice

Despite the prevalence of anxiety disorders, the molecular identity of neural circuits underlying anxiety remains unclear. The lateral hypothalamus (LH) is one brain region implicated in the regulation of anxiety, and our recent data found that chemogenetic activation of LH galanin neurons attenuated the stress response to a novel environment as measured by the marble burying test. Thus, we hypothesize that LH galanin neurons may contribute to anxiety-related behavior. We used chemogenetics and fiber photometry to test the ability of LH galanin neurons to influence anxiety and stress-related behavior. Chemogenetic activation of LH galanin neurons significantly decreased anxiety-like behavior in the elevated plus maze, open field test, and light dark test. However, LH galanin activation did not alter restraint stress induced HPA activation or freezing behavior in the fear conditioning paradigm. In vivo calcium monitoring by fiber photometry indicated that LH galanin neurons were activated by anxiogenic and/or stressful stimuli including tail suspension, novel mouse interaction, and predator odor. Further, in a fear conditioning task, calcium transients strongly increased during foot shock, but were not affected by the unconditioned stimulus tone. These data indicate that LH galanin neurons both respond to and modulate anxiety, with no influence on stress induced HPA activation or fear behaviors. Further investigation of LH galanin circuitry and functional mediators of behavioral output may offer a more refined pharmacological target as an alternative to first-line broad pharmacotherapies such as benzodiazepines.

Lateral septum as a nexus for mood, motivation, and movement

The lateral septum (LS) has been implicated in a wide variety of functions, including emotional, motivational, and spatial behavior, and the LS may regulate interactions between the hippocampus and other regions that mediate goal directed behavior. In this review, we suggest that the lateral septum incorporates movement into the evaluation of environmental context with respect to motivation, anxiety, and reward to output an 'integrated movement value signal'. Specifically, hippocampally-derived contextual information may be combined with reinforcement or motivational information in the LS to inform task-relevant decisions. We will discuss how movement is represented in the LS and the literature on the LS's involvement in mood and motivation. We will then connect these results to LS movement-related literature and hypotheses about the role of the lateral septum. We suggest that the LS may communicate a movement-scaled reward signal via changes in place-, movement-, and reward-related firing, and that the LS should be considered a fundamental node of affect and locomotor pathways in the brain.

Whole-brain mapping of projection from mouse lateral septal nucleus

The lateral septal nucleus (LS) plays a critical role in emotionality, social behavior and feeding processes, through neural connections with the hippocampus and hypothalamus. We investigated the neural circuits of LS by using herpes simplex virus 1 strain H129 (H129) and pseudorabies virus stain Bartha (PRV). Virus H129 indicates that LS directly projects to some cerebral nuclei (nucleus accumbens, bed nuclei of the stria terminalis and amygdala), part of the hypothalamus (median preoptic, paraventricular, dorsomedial nucleus and lateral area), thalamus (medial habenula, the paraventricular, parataenial and reuniens nuclei, and the medial line nuclei) and the pontine central gray. Then the LS has secondary projections to the CA3 and CA1 field of the hippocampal formation, lateral and medial preoptic area, and the mammillary body. PRV tracing shows that LS are mainly receiving primary inputs from the amygdala, hippocampus, hypothalamic, thalamus, midbrain and hindbrain, and secondary inputs from dorsal and central linear nucleus raphe, the lateral part of the superior central nucleus raphe, the ventral anterior-lateral complex, the intermediodorsal nucleus, the central medial nucleus, the rhomboid nucleus, and the submedial nucleus of the thalamus. The neural circuit data revealed here could help to understand and further research on the function of LS.

Summary: We identified the sequence of projections from the lateral septal nucleus by virus tracing and expanded the data on neural circuits, which could help to understand brain function.

Neuroligin-2 Determines Inhibitory Synaptic Transmission in the Lateral Septum to Optimize Stress-Induced Neuronal Activation and Avoidance Behavior

BACKGROUND

Investigations in the neocortex have revealed that the balance of excitatory and inhibitory synaptic transmission (E/I ratio) is important for proper information processing. The disturbance of this balance underlies many neuropsychiatric illnesses, including autism spectrum disorder and schizophrenia. However, little is known about the contribution of E/I balance to the functioning of subcortical brain regions, such as the lateral septum (LS), a structure that plays important roles in regulating anxiety-related behavior.

METHODS

We manipulated E/I balance in the mouse LS by localized conditional deletion of neuroligin-2, a postsynaptic cell adhesion protein located at gamma-aminobutyric acidergic synapses and important for inhibitory synaptic transmission. We then performed analyses of synaptic transmission in the LS, stress-induced expression of immediate early gene c-fos, and anxiety-related and depression-related behavior.

RESULTS

The absence of neuroligin-2 in the LS in the mature mouse brain resulted in postsynaptic impairment of inhibitory synaptic transmission. Importantly, the reduced inhibition and resulting E/I imbalance decreased the responsiveness of LS neurons to stress. Furthermore, this E/I imbalance in the LS was associated with impaired stress-induced activation of downstream hypothalamic nuclei and reduced avoidance behavior of the animals in the elevated plus maze.

CONCLUSIONS

Our results described the synaptic function of neuroligin-2 in the LS, uncovered a positive association between c-Fos-expressing neurons in the LS and downstream hypothalamic areas and avoidance behavior, and demonstrated that intact inhibitory synaptic transmission and proper E/I balance are required for the optimal functioning of this subcortical circuit.

The intake of water containing a mix of pollutants at environmentally relevant concentrations leads to defensive response deficit in male C57Bl/6J mice

Previous studies have individually confirmed the toxic effects from different pollutants on mammals. However, effects resulting from the exposure of these animals to multi-pollutant mixes have not been studied so far. Thus, the aim of the current study is to assess the effect from the chronic exposure (105days) of C57Bl/6J mice to a mix of pollutants on their response to potential predators. In order to do so, the following groups were formed: "control", "Mix 1× [compounds from 15 pollutants identified in surface waters at environmentally relevant concentration (ERC)]", "Mix 10×" and "Mix 25×" (concentrations 10 and 25 times higher than the ERC). From the 100th experimental day on, the animals were subjected to tests in order to investigate whether they showed locomotor, visual, olfactory and auditory changes, since these abilities are essential to their anti-predatory behavior. Next, the animals' behavior towards potential predators (Felis catus and Pantherophis guttatus) was assessed. The herein collected data did not show defensive response from any of the experimental groups to the predatory stimulus provided by P. guttatus. However, the control animals, only, presented anti-predatory behavior when F. catus was introduced in the apparatus, fact that suggests defensive response deficit resulting from the treatments. Thus, the current study is pioneer in showing that the chronic intake of water containing a mix of pollutants (even at low concentrations) leads to behavioral disorders able to affect the survival and population dynamics of mammalian species at ecological level.

Cerebral oxidative metabolism mapping in four genetic mouse models of anxiety and mood disorders

The psychopathology of depression is highly complex and the outcome of studies on animal models is divergent. In order to find brain regions that could be metabolically distinctively active across a variety of mouse depression models and to compare the interconnectivity of brain regions of wild-type and such genetically modified mice, histochemical mapping of oxidative metabolism was performed by the measurement of cytochrome oxidase activity. We included mice with the heterozygous knockout of the vesicular glutamate transporter (VGLUT₁^-/+), full knockout of the cannabinoid 1 receptor (CB1^-/-), an anti-sense knockdown of the glucocorticoid receptor (GRi) and overexpression of the human 5-hydroxytryptamine transporter (h5-HTT). Altogether 76 mouse brains were studied to measure oxidative metabolism in one hundred brain regions, and the obtained dataset was submitted to a variety of machine learning algorithms and multidimensional scaling. Overall, the top brain regions having the largest contribution to classification into depression model were the lateroanterior hypothalamic nucleus, the anterior part of the basomedial amygdaloid nucleus, claustrum, the suprachiasmatic nucleus, the ventromedial hypothalamic nucleus, and the anterior hypothalamic area. In terms of the patterns of inter-regional relationship between wild-type and genetically modified mice there was little overall difference, while the most deviating brain regions were cortical amygdala and ventrolateral and ventral posteromedial thalamic nuclei. The GRi mice that most clearly differed from their controls exhibited deviation of connectivity for a number of brain regions, such as ventrolateral thalamic nucleus, the intermediate part of the lateral septal nucleus, the anteriodorsal part of the medial amygdaloid nucleus, the medial division of the central amygdaloid nucleus, ventral pallidum, nucleus of the vertical limb of the diagonal band, anteroventral parts of the thalamic nucleus and parts of the bed nucleus of the stria terminalis. Conclusively, the GRi mouse model was characterized by changes in the functional connectivity of the extended amygdala and stress response circuits.

The exposure to water with cigarette residue changes the anti-predator response in female Swiss albino mice

Recent studies have shown that cigarette consumption affects much more than human health. Smoked cigarette butt (SCB) disposal into the environment can bring little-known negative biological consequences to mammals, since it contains many organic and inorganic toxic chemical constituents. Thus, we aim at assessing whether the ingestion of water with leached SCB for 60 days by female Swiss mice changes their defensive behavioral response to potential predators (cats and snakes). We worked with the following groups of animals: control (pollutant-free water), water with environmental concentration of SCB (1.9 μg/L of nicotine), and concentration 1000 times higher (EC1000×). Our data show that the treatments did not cause locomotor, visual, auditory, and olfactory deficit in the animals. However, we observed that the animals exposed to the pollutants did not present behavioral differences in the test session with or without the snake. On the other hand, animals in all groups showed defensive behavior when the test was conducted with the cat in the apparatus. However, female mice presented weaker response than the control. Thus, our data point towards the potential neurotoxic damage caused to mice who have ingested water with SCB residues, even at low concentrations.

Anxiety Cells in a Hippocampal-Hypothalamic Circuit

The hippocampus is traditionally thought to transmit contextual information to limbic structures where it acquires valence. Using freely moving calcium imaging and optogenetics, we show that while the dorsal CA1 subregion of the hippocampus is enriched in place cells, ventral CA1 (vCA1) is enriched in anxiety cells that are activated by anxiogenic environments and required for avoidance behavior. Imaging cells defined by their projection target revealed that anxiety cells were enriched in the vCA1 population projecting to the lateral hypothalamic area (LHA) but not to the basal amygdala (BA). Consistent with this selectivity, optogenetic activation of vCA1 terminals in LHA but not BA increased anxiety and avoidance, while activation of terminals in BA but not LHA impaired contextual fear memory. Thus, the hippocampus encodes not only neutral but also valence-related contextual information, and the vCA1-LHA pathway is a direct route by which the hippocampus can rapidly influence innate anxiety behavior.

Adversity in early adolescence promotes an enduring anxious phenotype and increases serotonergic innervation of the infralimbic medial prefrontal cortex

Stress during early development produces lasting effects on psychopathological outcomes. We analysed the impact of prior intermittent, physical stress (IPS) during early adolescence (PD 22-33) on anxiety-like behaviour of female rats in adulthood. After behavioural testing, we used immunohistochemistry for the 5-HT transporter (SERT) to evaluate 5-HT innervation profiles in the medial prefrontal cortex (mPFC) and ventral hippocampus (VH). Administration of IPS (i.e., water immersion, elevated platform, foot shock) in early adolescence increased rats' anxiety-like behaviour in the elevated plus-maze but had no effects in the shock-probe burying test. In the social interaction test, IPS decreased social interaction, and this effect was driven by selective decreases in the frequency of playfighting with no evident changes in contact and investigative behaviours. Selective stress-induced increases in the density of SERT-ir positive fibres were found in the infralimbic (IL) subregion of the mPFC but not in the cingulate or prelimbic (PL) subregions. IPS in early adolescence did not affect 5-HT innervation profiles in any sub-fields of the VH. Our findings confirm and extend on earlier evidence that stress during early adolescence promotes the emergence of an anxious phenotype and provide novel evidence that these effects are associated with increased 5-HT innervation of the IL mPFC.

The lateral hypothalamus to lateral habenula projection, but not the ventral pallidum to lateral habenula projection, regulates voluntary ethanol consumption

The lateral habenula (LHb) is an epithalamic brain region implicated in aversive processing via negative modulation of midbrain dopamine (DA) and serotonin (5-HT) systems. Given the role of the LHb in inhibiting DA and 5-HT systems, it is thought to be involved in various psychiatric pathologies, including drug addiction. In support, it has been shown that LHb plays a critical role in cocaine- and ethanol-related behaviors, most likely by mediating drug-induced aversive conditioning. In our previous work, we showed that LHb lesions increased voluntary ethanol consumption and operant ethanol self-administration and blocked yohimbine-induced reinstatement of ethanol self-administration. LHb lesions also attenuated ethanol-induced conditioned taste aversion suggesting that a mechanism for the increased intake of ethanol may be reduced aversion learning. However, whether afferents to the LHb are required for mediating effects of the LHb on these behaviors remained to be investigated. Our present results show that lesioning the fiber bundle carrying afferent inputs to the LHb, the stria medullaris (SM), increases voluntary ethanol consumption, suggesting that afferent structures projecting to the LHb are important for mediating ethanol-directed behaviors. We then chose two afferent structures as the focus of our investigation. We specifically studied the role of the inputs from the lateral hypothalamus (LH) and ventral pallidum (VP) to the LHb in ethanol-directed behaviors. Our results show that the LH-LHb projection is necessary for regulating voluntary ethanol consumption. These results are an important first step towards understanding the functional role of afferents to LHb with regard to ethanol consumption.

Repeated threat (without direct harm) alters metabolic capacity in select regions that drive defensive behavior

To understand the behavioral consequences of intermittent anticipatory stress resulting from threats without accompanying physiological challenges, we developed a semi-naturalistic rodent housing and foraging environment that can include threats that are unpredictable in timing. Behavior is automatically recorded while rats forage for food or water. Over three weeks, the threats have been shown to elicit risk assessment behaviors, increase defensive burying and increase adrenal gland weight. To identify brain regions activated by this manipulation, we measured cytochrome c oxidase (COX), which is tightly coupled to neural activity. Adolescent male Sprague-Dawley rats were randomly assigned to control (CT) or unpredictable threat/stress (ST) housing conditions consisting of two tub cages, one with food and another with water, separated by a tunnel. Over three weeks (P31-P52), the ST group received randomly timed (probability of 0.25), simultaneous presentations of ferret odor, an abrupt light, and sound at the center of the tunnel. The ST group had consistently fewer tunnel crossings than the CT group, but similar body weights. Group differences in COX activity were detected in regions implicated in the control of defensive burying. There was an increase in COX activity in the hypothalamic premammillary dorsal nucleus (PMD) and lateral septum (LS), whereas a decrease was observed in the periaqueductal gray (PAG) and CA3 region of the hippocampus. There were no significant differences in the anterior cingulate cortex, prefrontal cortex, striatum or motor cortex. The sites with changes in metabolic capacity are candidates for the sites of plasticity that may underlie the behavioral adaptations to intermittent threats.

Aggression and anxiety in adolescent AAS-treated hamsters: A role for 5HT3 receptors

Previously, we have shown that anabolic androgenic steroid (AAS) exposure throughout adolescence stimulates offensive aggression while also reducing anxious behaviors during the exposure period. Interestingly, AAS exposure through development correlates with alterations to the serotonin system in regions known to contain 5HT3 receptors that influence the control of both aggression and anxiety. Despite these effects, little is known about whether these separate developmental AAS-induced behavioral alterations occur as a function of a common neuroanatomical locus. To begin to address this question, we localized 5HT3 receptors in regions that have been implicated in aggression and anxiety. To examine the impact these receptors may have on AAS alterations to behavior, we microinjected the 5HT3 agonist mCPBG directly into a region know for its influence over aggressive behavior, the lateral division of the anterior hypothalamus, and recorded alterations to anxious behaviors using the elevated plus maze. AAS exposure primarily reduced the presence of 5HT3 receptors in aggression/anxiety regions. Accordingly, mCPBG blocked the anxiolytic effects of adolescent AAS exposure. These data suggest that the 5HT3 receptor plays a critical role in the circuit modulating developmental AAS-induced changes to both aggressive and anxious behaviors, and further implicates the lateral division of the anterior hypothalamus as an important center for the negative behavioral effects of developmental AAS-exposure.

Infusions of muscimol into the lateral septum do not reduce rats' defensive behaviors toward a cat odor stimulus

The lateral septum (LS) is implicated in behavioral defense. We tested whether bilateral infusions of the GABAA receptor agonist muscimol into the LS suppress rats' defensive responses to cat odor. Rats received intra-LS infusions of either saline or muscimol (40 ng/rat) and were exposed to either a piece of a cat collar that had been previously worn by a cat or to a control (cat odor free) collar. Rats exposed to the cat odor collar displayed more head-out postures, while intra-LS application of muscimol reduced the number of head-out postures. However, this reduction was also present in rats exposed to a control (cat odor free) collar. This latter finding suggests that despite its involvement in other defensive behaviors (e.g., open arm avoidance in the elevated plus maze), the LS does not selectively regulate rats' receptor defensive responding to the olfactory cues present in our cat odor stimulus.

Central stress-integrative circuits: forebrain glutamatergic and GABAergic projections to the dorsomedial hypothalamus, medial preoptic area, and bed nucleus of the stria terminalis

Central regulation of hypothalamo-pituitary-adrenocortical (HPA) axis stress responses is mediated by a relatively circumscribed group of projections to the paraventricular hypothalamus (PVN). The dorsomedial hypothalamus (DMH), medial preoptic area (mPOA), and bed nucleus of the stria terminalis (BST) provide direct, predominantly inhibitory, innervation of the PVN. These PVN-projecting neurons are controlled by descending information from limbic forebrain structures, including the prefrontal cortex, amygdala, hippocampus, and septum. The neurochemical phenotype of limbic circuits targeting PVN relays has not been systematically analyzed. The current study combined retrograde tracing and immunohistochemistry/in situ hybridization to identify the specific sites of glutamatergic and GABAergic inputs to the DMH, mPOA, and BST. Following Fluoro-gold (FG) injections in the DMH, retrogradely labeled cells co-localized with vesicular glutamate transporter mRNA in the prefrontal cortex, ventral hippocampus, and paraventricular thalamus. Co-localization of FG and glutamic acid decarboxylase mRNA was present throughout the central and medial amygdaloid nuclei and septal area. In addition, the mPOA received predominantly GABAergic input from the septum, amygdala, and BST. The BST received glutamatergic projections from the hippocampus and basomedial amygdala, whereas, GABAergic inputs arose from central and medial amygdaloid nuclei. Thus, discrete sets of neurons in the hypothalamus and BST are positioned to summate limbic inputs into PVN regulation and may play a role in HPA dysfunction and stress-related illness.

Diverging neural pathways assemble a behavioural state from separable features in anxiety

Behavioural states in mammals, such as the anxious state, are characterized by several features that are coordinately regulated by diverse nervous system outputs, ranging from behavioural choice patterns to changes in physiology (in anxiety, exemplified respectively by risk-avoidance and respiratory rate alterations). Here we investigate if and how defined neural projections arising from a single coordinating brain region in mice could mediate diverse features of anxiety. Integrating behavioural assays, in vivo and in vitro electrophysiology, respiratory physiology and optogenetics, we identify a surprising new role for the bed nucleus of the stria terminalis (BNST) in the coordinated modulation of diverse anxiety features. First, two BNST subregions were unexpectedly found to exert opposite effects on the anxious state: oval BNST activity promoted several independent anxious state features, whereas anterodorsal BNST-associated activity exerted anxiolytic influence for the same features. Notably, we found that three distinct anterodorsal BNST efferent projections-to the lateral hypothalamus, parabrachial nucleus and ventral tegmental area-each implemented an independent feature of anxiolysis: reduced risk-avoidance, reduced respiratory rate, and increased positive valence, respectively. Furthermore, selective inhibition of corresponding circuit elements in freely moving mice showed opposing behavioural effects compared with excitation, and in vivo recordings during free behaviour showed native spiking patterns in anterodorsal BNST neurons that differentiated safe and anxiogenic environments. These results demonstrate that distinct BNST subregions exert opposite effects in modulating anxiety, establish separable anxiolytic roles for different anterodorsal BNST projections, and illustrate circuit mechanisms underlying selection of features for the assembly of the anxious state.

Anxiety in Parkinson's disease: a critical review of experimental and clinical studies

Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting about 1% of the population older than 60 years. Classically, PD is considered as a movement disorder, and its diagnosis is based on the presence of a set of cardinal motor signs that are the consequence of a pronounced death of dopaminergic neurons in the substantia nigra pars compacta. There is now considerable evidence showing that the neurodegenerative processes leading to sporadic PD begin many years before the appearance of the characteristic motor symptoms, and that additional neuronal fields and neurotransmitter systems are also involved in PD, including olfactory structures, amygdala, caudal raphe nuclei, locus coeruleus, and hippocampus. Accordingly, adrenergic and serotonergic neurons are also lost, which seems to contribute to the anxiety in PD. Non-motor features of PD usually do not respond to dopaminergic medication and probably form the major current challenge in the clinical management of PD. Additionally, most studies performed with animal models of PD have investigated their ability to induce motor alterations associated with advanced phases of PD, and some studies begin to assess non-motor behavioral features of the disease. The present review attempts to examine results obtained from clinical and experimental studies to provide a comprehensive picture of the neurobiology and current and potential treatments for anxiety in PD. The data reviewed here indicate that, despite their high prevalence and impact on the quality of life, anxiety disorders are often under-diagnosed and under-treated in PD patients. Moreover, there are currently few clinical and pre-clinical studies underway to investigate new pharmacological agents for relieving these symptoms, and we hope that this article may inspire clinicians and researchers devote to the studies on anxiety in PD to change this scenario. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Lesions of the dorsal lateral septum do not affect neophagia in the novelty induced suppression of feeding paradigm but reduce defensive behaviours in the elevated plus maze and shock probe burying tests

Past studies have shown that the lateral septum is involved in anxiety. Here, we tested whether the dorsal lateral septum contributes to neophagia by using the novelty induced suppression of feeding (NISF) paradigm. We found that while lesions of the dorsal lateral septum did not affect home or novel cage responding in the NISF test, they did decrease open arm avoidance in the elevated plus maze and burying in the shock probe burying test. Our results suggest that the dorsal lateral septum does not regulate neophagia in the NISF, but further experiments are needed to determine if the same is true for the intermediate and ventral lateral septum.

Exercise effects on motor and affective behavior and catecholamine neurochemistry in the MPTP-lesioned mouse

This study used 1-methyl-4-phenyl-1,2,3,6,-tetrahydropyridine (MPTP) in mice to determine if exercise improves behavior and dopamine (DA) and serotonin (5HT) content. Male C57BL/6 mice received MPTP (4 x 20mg/kg) or saline. They remained sedentary or exercised by treadmill or voluntary running wheel for 6 weeks (n=8/group). Saline-treated mice ran significantly faster on running wheels (22.8+/-1.0m/min) than on treadmill (8.5+/-0.5m/min), and MPTP lesion did not reduce voluntary exercise (19.3+/-1.5m/min, p>0.05). There was a significant effect of both lesion and exercise on overall Rotarod performance (ORP): MPTP lesion reduced ORP, while treadmill exercise increased ORP vs sedentary mice (p<0.05). MPTP increased anxiety in the marble-burying test: sedentary lesioned mice buried more marbles (74.0+/-5.2%) than sedentary controls (34.8+/-11.8%, p<0.05). Conversely, exercise reduced anxiety on the elevated plus maze. Among saline-treated mice, those exposed to voluntary wheel-running showed an increased percent of open arm entries (49.8+/-3.5%, p<0.05) relative to sedentary controls (36.2+/-4.0%, p<0.05). Neither MPTP nor exercise altered symptoms of depression measured by sucrose preference or tail suspension. MPTP significantly reduced DA in striatum (in sedentary lesioned mice to 42.1+/-3.0% of saline controls), and lowered 5HT in amygdala and striatum (in sedentary lesioned mice to 86.1+/-4.1% and 66.5+/-8.2% of saline controls, respectively); exercise had no effect. Thus, exercise improves behavior in a model of DA depletion, without changes in DA or 5HT.