Research Article: Open Source Tools and Methods | Novel Tools and Methods OpenVape: an Open-Source E-Cigarette Vapour Exposure Device for Rodents https://doi.org/10.1523/ENEURO.0279-20.2020 Cite as: eNeuro 2020; 10.1523/ENEURO.0279-20.2020 Received: 27 June 2020 Revised: 30 July 2020 Accepted: 18 August 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.eneuro.org/alerts to receive customized email alerts when the fully formatted version of this article is published. Copyright © 2020 Frie 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. 1 Manuscript Title Page Instructions 2 1. Manuscript Title (50 word maximum) 3 4 OpenVape: an Open-Source E-Cigarette Vapour Exposure Device for Rodents 5 2. Abbreviated Title (50 character maximum) 6 7 OpenVape: an Open-Source Vapour Exposure Device 8 3. List all Author Names and Affiliations in order as they would appear in the published article 9 10 Jude A. Frie – Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, 11 Ontario, Canada. 12 Jacob Underhill – Department of Biomedical Sciences, Ontario Veterinary College, University of 13 Guelph, Ontario, Canada. 14 Bin Zhao – Departments of Pharmacology and Toxicology, University of Toronto, Ontario, Canada 15 Giordano de Guglielmo – Department of Psychiatry, University of California, San Diego, San Diego, 16 California, USA. 17 Rachel F. Tyndale – Departments of Pharmacology and Toxicology, and Psychiatry, University of 18 Toronto, Ontario, Canada; Centre for Addiction and Mental Health, Toronto, Canada. 19 Jibran Y. Khokhar – Department of Biomedical Sciences, Ontario Veterinary College, University of 20 Guelph, Ontario, Canada. 21 4. Author Contributions: JAF, JU and JYK: Designed Research, Performed research, Contributed 22 unpublished reagents/ analytic tools, Analyzed data, Wrote the paper. BZ: Performed Research. 23 GdG: Designed Research. RFT: Performed Research, Wrote the Paper. 24 25 5. Correspondence should be addressed to (include email address) 26 27 Dr. Jibran Khokhar 28 Department of Biomedical Sciences 29 Ontario Veterinary College 30 University of Guelph 31 50 Stone Rd. E. 32 Guelph, ON 33 N1G1C5 34 [email protected] 35 36 1 37 38 6. Acknowledgements 39 We would like to thank Judy Chen and Ariel Oren for their assistance with CPP 40 experiments. 41 42 7. Conflict of Interest 43 44 A. No (State ‘Authors report no conflict of interest’) 45 46 B. Yes (Please explain) 47 48 Yes – RF Tyndale has consulted for Quinn Emanuel and Ethismos Research Inc on 49 unrelated topics. 50 8. Funding sources 51 This work was supported by a Discovery Grant from the Natural Sciences and Engineering 52 Research Council award (RGPIN-2019-05121) to JYK. This research was undertaken, in 53 part, thanks to funding from the Canada Research Chairs program (RFT, CRC in 54 Pharmacogenomics) and a Canadian Institutes of Health Research (Foundation grant FDN- 55 154294). 56 1 57 58 Visual Abstract 59 60 Abstract 61 The prevalence of "vaping" has recently seen significant increases in North America, especially 62 in adolescents. However, the behavioural correlates of vaping are largely unexplored. The uptake 63 of existing technologies meant for rodent vapour inhalation remains limited due to a lack of 64 affordability and versatility (ability to be used with a variety of vapourizers). The OpenVape 65 offers an open-source, low-cost solution that can be used in a variety of research contexts. Here 66 we present a specific use case, combining the OpenVape apparatus with JUUL e-cigarettes. This 67 apparatus consists of Arduino-operated vacuum pumps that deliver vapour directly from e- 68 cigarettes to exposure chambers. The OpenVape is easy to build and customize for any type of 69 vapourizer (e.g., nicotine pod or tank; cannabis flower or concentrates). To test the OpenVape, 70 we performed biochemical verification and behavioural studies. The behavioural test 2 71 (conditioned place preference) was conducted using adolescent and adult animals to assess 72 developmental differences in the rewarding effects of nicotine vapour, as previously observed 73 with injected nicotine. These findings demonstrate that even after brief exposures to nicotine 74 vapour, pharmacologically relevant nicotine and cotinine levels could be detected in plasma, and 75 significant conditioned place preference was observed, especially in adolescent rats which 76 showed preference at shorter puff delivery durations (lower nicotine doses) compared to adults. 77 Together, these findings suggest that OpenVape provides an affordable, open-source option for 78 pre-clinical behavioural research into the effects of vaping. 79 Significance Statement 80 With the recent increases in popularity of vaping, behavioural and neurobiological studies in 81 preclinical models will be pivotal in exploring the impacts of this use. While there are 82 commercially available vapour exposure equipment, they can be prohibitively expensive and 83 often require proprietary software. The OpenVape (OV) is able to deliver regulated doses of 84 vapour into a standard animal cage with minimal operator intervention. The OV is also open- 85 source, easy to build, inexpensive, and can be used in a variety of research contexts due to its 86 small physical footprint. In this study, we validate its efficacy using JUUL e-cigarettes, showing 87 that animals achieve meaningful nicotine levels, and that both adolescent and adult animals 88 display conditioned place preference to the nicotine vapour. 89 Introduction 90 In recent years, adolescent e-cigarette use has increased dramatically, with past 30-day nicotine 91 vaping among US high school students growing from 11.7% to 27.5% between 2017 and 2019 92 (Wang et al., 2019). Currently, the most popular e-cigarette is the JUUL, maintaining 76% of the 3 93 US e-cigarette market (Craver, 2019). JUUL’s adolescent appeal has been attributed to their 94 sleek/discreet design (Kavuluru et al., 2019). influential marketing (Mantey et al., 2016; Huang 95 et al., 2019), appealing flavours (Leavens et al., 2019), and high nicotine content (Kong et al., 96 2019). Additionally, JUUL’s have been shown to deliver significantly more nicotine to the 97 bloodstream compared to traditional cigarettes (Rao et al., 2020). 98 Adolescence is thought to be a period of increased sensitivity to the rewarding effects of nicotine 99 (Thorpe et al., 2020). Indeed, nearly 90% of cigarette smokers initiate smoking before the age of 100 18 (Substance Abuse and Mental Health Services Administration, 2013). Adolescent smokers 101 also increase cigarette intake faster than adults (DiFranza et al., 2000), and report more positive 102 and less aversive experiences to initial cigarette exposures (Benowitz, 1999) Animal studies 103 support this data, with adolescent animals consistently showing both greater preference, and 104 preference across a larger range of doses during nicotine conditioned place preference (CPP) 105 compared to adults, a measure of the reward-like (hedonic value) properties of a drug (Vastola et 106 al., 2002; Belluzzi et al., 2004; Shram et al., 2006; Brielmaier et al., 2007; Kota et al., 2007, 107 2008; Torres et al., 2008; Shram and Lê, 2010; Ahsan et al., 2014). While beneficial in 108 understanding the rewarding effects of nicotine, these studies may not capture what makes 109 nicotine vapour rewarding in adolescents. The current study improves upon the translatability of 110 findings by directly exposing rats to the most popular e-cigarette available – JUUL. No studies to 111 date have assessed the developmental differences in nicotine vapour preference, partly owing to 112 limited options for exposing rodents to nicotine vapour. 113 Current commercially available nicotine vapour exposure apparatuses (e.g. DSI Buxco, SCIREQ 114 inExpose, LJARI eVape) are prohibitively expensive and require proprietary hardware and 115 software to operate, thereby limiting their accessibility and versatility. This has led others to 4 116 create customized alternatives (Manwell et al., 2014; Liu et al., 2016; Nguyen et al., 2016; Hage 117 et al., 2017; Lefever et al., 2017; Hilpert et al., 2019). However, these alternatives are still very 118 expensive, complicated to construct, and are not always open-source. Thus, in order to address 119 these issues, we created OpenVape (OV) – an affordable, open-source vapour delivery system. 120 OV can be made for ~$230, is easily constructed/operated, and is highly versatile (can be used 121 with a variety of vaping devices and products). It is also open-source, encouraging the 122 community to continue to add functionality as required. Here we provide the instructions to build 123 the simplest version of OV and provide a relevant behavioural validation showing the 124 developmental differences in nicotine’s reward-like properties during a CPP task. We also show 125 that OV is capable of producing pharmacologically relevant blood nicotine and cotinine levels 126 following short periods of vapour exposure. 127 Materials and Methods 128 Animals 129 For the pharmacokinetic study, 15 adult male Sprague (Charles River, Quebec) were used. These 130 rats were housed in pairs and given ad libitum access to standard chow and water. For the age- 131 dependent CPP study, a total of 48 male Sprague-Dawley rats were used, consisting of 24 adults 132 and 24 adolescents. These rats were housed in groups of 4 (to maintain consistency between 133 adult and adolescent rats) and given access to standard chow and water. All animal procedures 134 were performed in accordance with the [Author University] animal care committee's regulations. 135 Device Design 5 136 The OV device requires one standard wall receptacle for power.