Research Articles: Behavioral/Cognitive Corticosterone Attenuates Reward-seeking Behavior and Increases Anxiety via D2 Receptor Signaling in Ventral Tegmental Area Dopamine Neurons https://doi.org/10.1523/JNEUROSCI.2533-20.2020 Cite as: J. Neurosci 2020; 10.1523/JNEUROSCI.2533-20.2020 Received: 26 September 2020 Revised: 8 December 2020 Accepted: 14 December 2020 This Early Release article has been peer-reviewed and accepted, but has not been through the composition and copyediting processes. The final version may differ slightly in style or formatting and will contain links to any extended data. Alerts: Sign up at www.jneurosci.org/alerts to receive customized email alerts when the fully formatted version of this article is published. Copyright © 2020 Peng et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed. Corticosterone Attenuates Reward-seeking Behavior and Increases Anxiety via D2 Receptor Signaling in Ventral Tegmental Area Dopamine Neurons Abbreviated title: CORT Attenuates Reward-seeking via D2R in VTA Beibei Peng1,3, Qikuan Xu1,3, Jing Liu1,3, Sophie Guo4, Stephanie L. Borgland4, Shuai Liu1,2,3,5 1. Key Laboratory of Brain Functional Genomics (MOE&STCSM), Affiliated Mental Health Center (ECNU), School of Psychology and Cognitive Science, East China Normal University, Shanghai, 200062, China 2. Shanghai Changning Mental Health Center, Shanghai, 200042, China 3. NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, Shanghai, 200062, China 4. Department of Physiology & Pharmacology, Hotchkiss Brain Institute, Cumming School of medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada 5. To whom correspondence should be addressed: Shuai Liu (Email: [email protected]) Number of pages: 39 pages Number of figures: 11 figures Number of words for abstract: 234 words Number of words for introduction: 413 words Number of words for discussion: 1495 words 1 Conflict of interest statement The authors declare no competing interests. Acknowledgments The work was sponsored by National Natural Science Foundation of China (31800856), Shanghai Pujiang Program (18PJ1402600), the Key Specialist Projects of Shanghai Municipal Commission of Health and Family Planning (ZK2015B01) and the Programs Foundation of Shanghai Municipal Commission of Health and Family Planning (201540114). S.L. acknowledges the support of the NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai. S.L.B is supported by a Tier I Canada Research Chair and an operating grant from Canadian Institutes of Health Research FDN-147473. This work was also supported by the HBI’s fund for depression research (SLB). 2 1 Abstract 2 Corticosteroids have been widely used in anti-inflammatory medication. Chronic 3 corticosteroid (CORT) treatment can cause mesocorticolimbic system dysfunctions 4 which is known to play a key role for the development of psychiatric disorders. The 5 ventral tegmental area (VTA) is a critical site in the mesocorticolimbic pathway and is 6 responsible for motivation and reward-seeking behaviors. However, the mechanism 7 by which chronic CORT alters VTA dopamine neuronal activity is largely unknown. 8 We treated peri-adolescent male mice with either vehicle, 1d, or 7d CORT in the 9 drinking water, examined behavioral impacts with light/dark box, elevated plus maze, 10 operant chamber and open field tests, measured the effects of CORT on VTA 11 dopamine neuronal activity using patch clamp electrophysiology and dopamine 12 concentration using fast-scan cyclic voltammetry, and tested the effects of dopamine 13 D2 receptor (D2R) blockade by intra-VTA infusion of a D2R antagonist. CORT 14 treatment induced anxiety-like behavior as well as decreased food-seeking behaviors. 15 We show that chronic CORT treatment decreased excitability and excitatory synaptic 16 transmission onto VTA dopamine neurons. Furthermore, chronic CORT increased 17 somatodendritic dopamine concentration. The D2R antagonist sulpiride restored 18 decreased excitatory transmission and excitability of VTA dopamine neurons. 19 Furthermore, sulpiride decreased anxiety-like behaviour and rescued food-seeking 20 behaviour in mice with chronic CORT exposure. Taken together, 7d CORT treatment 21 induces anxiety-like behavior and impairs food-seeking in a mildly aversive 22 environment. D2R signaling in the VTA might be a potential target to ameliorate 3 23 chronic CORT induced anxiety and reward-seeking deficits. 24 25 Significance Statement 26 With widespread anti-inflammatory effects throughout body, corticosteroids 27 (CORT) have been used in a variety of therapeutic conditions. However, long term 28 corticosteroid treatment causes cognitive impairments and neuropsychiatric disorders. 29 The impact of chronic CORT on the mesolimbic system has not been elucidated. Here, 30 we demonstrate that 7-day CORT treatment increases anxiety-like behavior and 31 attenuates food-seeking behavior in a mildly aversive environment. By elevating local 32 dopamine concentration in the ventral tegmental area (VTA), a region important for 33 driving motivated behaviour, CORT treatment suppresses excitability and synaptic 34 transmission onto VTA dopamine neurons. Intriguingly, blockade of D2 receptor 35 signaling in the VTA restores neuronal excitability and food-seeking and alleviates 36 anxiety-like behaviors. Our findings provide a potential therapeutic target for 37 corticosteroid induced reward deficits. 4 38 Introduction: 39 Corticosteroids (CORT) have been used for a variety of conditions, such as 40 pneumonia, asthma, severe allergies and arthritis, due to its widespread anti- 41 inflammatory effects (Rhen and Cidlowski, 2005). However, long-term exposure to 42 CORT medications may cause side effects, including cognitive impairments and 43 neuropsychiatric disorders (Sonino and Fava, 2001; Coluccia et al., 2008; Pivonello et 44 al., 2015; Yasir and Sonthalia, 2019). While the physiological effects of acute CORT 45 in the brain are well documented (Mitra and Sapolsky, 2008; Kim et al., 2014; Myers 46 et al., 2014; Joels, 2018), the impact of longer-term CORT treatment, consistent with 47 systemic anti-inflammatory treatment, on the mesolimbic system has not been 48 elucidated. 49 Ventral tegmental area (VTA) dopamine neurons play an important role in 50 learning the incentive value of stimuli or actions to guide motivated behaviour and 51 thus play key roles in addiction and mood disorders. These neurons are highly 52 sensitive to corticotropin releasing factor and stress (reviewed in (Polter and Kauer, 53 2014; Hollon et al., 2015)), yet less is known about how they respond to 54 glucocorticoids. CORT activates glucocorticoid (GR) or mineralocorticoid receptors 55 (MR) and these receptors are subsequently translocated to the nucleus and act as 56 transcription factors (McEwen et al., 1986). However, rapid non-genomic cellular 57 mechanisms have been observed upon activation of GRs (Tasker and Herman, 2011). 58 Several lines of evidence indicate that the midbrain dopamine system could be 59 implicated in impairments associated with chronic CORT treatment. Both MRs and 5 60 GRs are expressed in a subset of VTA dopamine neurons (Harfstrand et al., 1986; 61 Ronken et al., 1994; Hensleigh and Pritchard, 2013). Activation of GRs by either in 62 vivo injection or acute incubation of VTA slices with dexamethasone potentiates 63 synaptic strength onto dopamine neurons (Daftary et al., 2009). Furthermore, stress- 64 induced plasticity in the VTA is blocked by administration of a GR antagonist (Saal et 65 al., 2003). Acute CORT application potentiated NMDA currents in VTA slices (Cho 66 and Little, 1999) and NMDA neurotoxicity of VTA neurons in organotypic VTA and 67 nucleus accumbens co-cultures (Berry et al., 2016). Because major depressive 68 disorder and reduced motivation are frequently reported in patients with CORT 69 treatment-induced Cushing syndrome (Wagenmakers et al., 2012; Pivonello et al., 70 2015), chronic CORT treatment may dysregulate dopamine signaling to influence 71 behaviour. However, little is known how chronic CORT treatment influences synaptic 72 transmission in the VTA. In the present study, we tested the hypothesis that chronic 73 CORT exposure impacts VTA neurophysiology and reward-seeking behaviors using 74 an oral CORT treatment mouse model (Gourley et al., 2008; Kinlein et al., 2017). 75 76 Materials and Methods 77 Animals and CORT Treatment 78 All protocols were in accordance with the ethical guidelines established by the 79 Canadian Council for Animal Care and were approved by the University of Calgary 80 Animal Care Committee and by the East China Normal University Animal Care 81 Committee. P21 male C57BL6 mice obtained from Charles River Laboratories or The 6 82 Jackson Laboratory (Quebec, Canada and Shanghai, China) were housed in a 12-hour 83 light/12-hour dark cycle in a temperature- and humidity-controlled environment with 84 food and water freely available. All efforts were made to minimize animal suffering 85 and reduce the number of animals used. Oral CORT treatment was conducted by 86 replacing drinking water with either 100 μg/ml CORT dissolved in ethanol (1% 87 ethanol final concentration) or vehicle (1% ethanol solution) (Kinlein et al., 2017; 88 Moda-Sava et al., 2019). Body weight, food consumption and water intake were 89 measured.