Research paperNeuropeptide Y neurons in the nucleus accumbens modulate anxiety-like behavior
Introduction
Neuropeptide Y (NPY) is a highly conserved 36-amino acid peptide that is expressed widely in the central nervous system. Several lines of evidence demonstrate that NPY exerts an anxiolytic-like effect (Heilig, 2004; Kask et al., 2002). For example, intracerebroventricular (ICV) administration of NPY in rats induces strong preference for the open arms in the elevated plus maze test (EPM), which is one of the most widely used behavioral paradigms for assessing anxiety-like behavior (Broqua et al., 1995). Center distance is significantly reduced in NPY knockout (KO) mice relative to wild-type (WT) mice in the open field test (OFT), which is another common test for anxiety-like behavior in rodents (Bannon et al., 2000). ICV administration of NPY increases food intake and produces anxiolytic-like behavior in rats, but microinjection of NPY into the amygdala has only an anxiolytic effect (Heilig et al., 1993), suggesting that distinct mechanisms underlie NPY-mediated regulation of food intake and anxiety-like behavior. The role of NPY neurons in the hypothalamic arcuate nucleus in the regulation of food intake has been extensively studied (Gehlert, 1999; Inui, 1999; Kalra et al., 1999). On the other hand, it is difficult to elucidate where NPY neurons related to anxiety located in by the pharmacological experiments, even if NPY neurons locate in the anxiety-related brain regions, such as amygdala and dorsal periaqueductal gray (Kask et al., 2002).
The nucleus accumbens (NAc), which has a central role in reward systems (Sesack and Grace, 2010), is an area of the brain rich in NPY-expressing cells (Chronwall et al., 1985; de Quidt and Emson, 1986; Morris, 1989). We previously demonstrated that NPY-containing neurons are distributed in both the core and shell of the NAc (Aoki et al., 2016). In addition, we analyzed the behavior of transgenic mice expressing an unedited RNA isoform of the 5-HT2C receptor, and found that these mice showed a reduction in NPY gene expression in the NAc and exhibited behavioral despair (Aoki et al., 2016). Likewise, ICV administration of cholecystockinin-4 causes a decrease in NPY-immunoreactive fibers and cell bodies in the NAc and induces anxiety-like behaviors (Desai et al., 2014). These observations suggest that NAc NPY neurons may be linked to mood disorders.
In the present study, to directly investigate functional role of NAc NPY neurons, we constructed adeno-associated virus (AAV) encoding Cre-dependent diphtheria toxin receptor (DTR) and performed region-specific ablation of NAc NPY neurons using NPY-Cre mice and diphtheria toxin (DT)-mediated cell ablation/dysfunction technique. Moreover, using designer receptors exclusively activated by designer drugs (DREADD) technology, we examine the impact of the activation of NAc NPY neurons on anxiety-like behavior.
Section snippets
Animals
To produce NPY-Cre mice, B6.FVB(Cg)-Tg(NPY-cre)RH26Gsat/Mmucd (037423-UCD, NPY-Cre) sperm was purchased from Mutant Mouse Resource & Research Centers (CA, USA). We entrusted the generation of NPY-Cre mice using the sperm to the RIKEN BioResource Research Center (Ibaraki, Japan). The mice were kept under a 12-h light/dark cycle (lights on at 08:00). Standard food pellets and water were provided ad libitum. Behavioral testing was performed between 10:00 and 13:00. All animal procedures, including
DT-mediated specific ablation of NAc NPY neurons
We constructed and injected an AAV encoding a Cre-dependent hDTR fused to an EGFP reporter into the NAc (Fig. 1A). Injection of the AAV into the NAc in the NPY-Cre mice induced specific expression of DTR-EGFP in NAc NPY neurons (Fig. 1B). Immunohistochemical analysis revealed that NPY-immunoreactive cells and fibers were densely localized in the NAc of DT-treated mCherry mice (Fig. 1C, left), while only a few NPY-immunoreactive cells were found in DT-treated NPY-DTR mice (Fig. 1C, right). The
Discussion
The NAc participates in various neurobehavioral functions, including wakefulness (Luo et al., 2018), motivation (Tsutsui-Kimura et al., 2017) and anxiety/depression (Feng et al., 2017). Although histological studies show that there are many NPY cell bodies and fibers in the NAc (Chronwall et al., 1985; de Quidt and Emson, 1986; Morris, 1989), their function remained unclear. Here, we show that mice with ablation of NPY neurons in the NAc exhibit an increase in anxiety-like behavior. We also
Declaration of Competing Interest
The authors declare that they have no conflict of interest.
Acknowledgments
This work was supported by the Japan Society for the Promotion of Science Grants-in-Aid [grant no. 17H03553 to M.T. and grant no. 19K09032 to S.Y.].
Author contributions
S.Y., M.S., N.K., S.B., and Y.O. performed histological and behavioral experiments. A.T. generated the AAV. Y.W. supported behavioral experiments and provided the advice. S.Y. and M.T. wrote the paper. M.T. supervised the whole study.
References (29)
- et al.
Dopamine transporter (DAT) knockdown in the nucleus accumbens improves anxiety- and depression-related behaviors in adult mice
Behav. Brain Res.
(2019) - et al.
Behavioral characterization of neuropeptide Y knockout mice
Brain Res.
(2000) - et al.
The anatomy of neuropeptide-Y-containing neurons in rat brain
Neuroscience
(1985) - et al.
Distribution of neuropeptide Y-like immunoreactivity in the rat central nervous system--II. Immunohistochemical analysis
Neuroscience
(1986) - et al.
Neuropeptide Y attenuates anxiety- and depression-like effects of cholecystokinin-4 in mice
Neuroscience
(2014) Role of hypothalamic neuropeptide Y in feeding and obesity
Neuropeptides
(1999)Antisense inhibition of neuropeptide Y (NPY)-Y1 receptor expression blocks the anxiolytic-like action of NPY in amygdala and paradoxically increases feeding
Regul. Pept.
(1995)The NPY system in stress, anxiety and depression
Neuropeptides
(2004)Feeding and body-weight regulation by hypothalamic neuropeptides--mediation of the actions of leptin
Trends Neurosci.
(1999)- et al.
The neurocircuitry and receptor subtypes mediating anxiolytic-like effects of neuropeptide Y
Neurosci. Biobehav. Rev.
(2002)
Striatal interneurones: chemical, physiological and morphological characterization
Trends Neurosci.
Expression of G protein-coupled receptor 30 in the spinal somatosensory system
Brain Res.
Involvement of rat dopaminergic system of nucleus accumbens in nicotine-induced anxiogenic-like behaviors
Brain Res.
Involvement of serotonin 2C receptor RNA editing in accumbal neuropeptide Y expression and behavioural despair
Eur. J. Neurosci.
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Cross talk about the role of Neuropeptide Y in CNS disorders and diseases
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2022, NeuropharmacologyCitation Excerpt :Previous research in rodents has described the prosocial effects of NPY as stemming from its anxiolytic properties (Desai et al., 2014; Sajdyk et al., 1999; Reichmann and Holzer, 2016). NAc NPY may act in a similar manner, as activation of NAc NPY-expressing interneurons results in an anxiolytic phenotype (Yamada et al., 2020). Beyond anxiety, it is also possible that the increase in social interaction seen following intra-NAc NPY infusion results from an increase in the rewarding properties of the encounter.
Neuropeptide Y, calcitonin gene-related peptide, and neurokinin A in brain regions of HAB rats correlate with anxiety-like behaviours
2022, European NeuropsychopharmacologyCitation Excerpt :The finding of increased NPY was in contrast to the decreased NPY expression found in animal models of depression and in post-traumatic stress disorder (Cohen et al., 2012; Husum et al., 2008, 2002). In addition, NPY neuron ablation in mouse NAc caused increased anxiety-like behaviours, whereas DREADD-mediated activation of the same neurons reversed the effect (Yamada et al., 2020). Along the same line, mice lacking NPY display an anxiogenic-like phenotype (Bannon et al., 2000).
Chronic oral nicotine administration and withdrawal regulate the expression of neuropeptide Y and its receptors in the mesocorticolimbic system
2021, NeuropeptidesCitation Excerpt :Aoki et al. (2016) reported that transgenic mice, which exhibited decreased NPY gene expression in the NAc, displayed behavioral despair in the forced swimming test, and accumbal NPY overexpression relieved the behavioral despair. Additionally, in a recent study by Yamada et al. (2020) ablation of NAc NPY neurons increased anxiety-like behavior in the open field and EPM tests whereas a decrease was observed by chemogenetic activation of the same neurons. In the present study, Y1 and Y2 mRNA expression levels were upregulated 48 h after the withdrawal.
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2021, Journal of Nutritional BiochemistryCitation Excerpt :Similarly, the expression of NPY is also altered by antibiotic-induced dysbiosis [47]. Interestingly, NPY and galanin also have been linked with addiction and anxiety behaviors, commonly observed in obese individuals [48–52]. Together these results highlights the association between gut microbiota, hypothalamic neuropeptides and behavior, and their importance to the development of obesity.