Chronic pain is a debilitating disease with current treatments lacking efficacy and safety, therefore discovery of new treatments is crucial. Initial studies suggest that psychedelics may be feasible for targeting pain, however clinical and preclinical controlled studies are necessary to further investigate that possibility. In this study we assessed the effects of two classical psychedelics psilocybin and 2,5-Dimethoxy-4-iodoamphetamine (DOI) in two models of chronic pain after systemic administration in male and female mice. Psilocybin and DOI dose-dependently reversed mechanical and cold hypersensitivity in the chemotherapy-induced peripheral neuropathy (CIPN) mouse model with different time-course of action. Similarly, psilocybin and DOI dose-dependently reversed thermal hypersensitivity in the chronic inflammatory mouse model of Complete Freud's Adjuvant (CFA). The effects of Psilocybin and DOI in both models were mediated by activation of 5-HT2A receptors (5-HT2AR). Overall, the present study suggests that classical psychedelics psilocybin and DOI are effective in reducing pain-like behaviors via 5-HT2AR activation in two mouse models of chronic pain.

Nicotine use remains one of the leading causes of preventable deaths in the United States and, while the prevalence of combustible cigarette use has declined over the past few years, the popularity of electronic nicotine delivery systems continues to rise. Vaping is not without risks, and its long-term effects, particularly in vulnerable populations, remain largely unknown. This study introduces a novel, oronasal-restricted, nicotine vapor self-administration mouse model to investigate the impact of nicotine concentration, genotype, sex, and age on self-administration and behavioral response to nicotine. Our studies show that male and female young adult mice respond to nicotine, demonstrating notable sex-related differences in intake, locomotor sensitization, and somatic withdrawal signs. In addition, we characterized intake in adolescent mice, showing sex differences as well. Finally, we showed genotype-related differences when using β2 knock-out mice, emphasizing the role of the β2 nAChR in nicotine reward and nicotine intake. This new model offers a more targeted approach to studying the potential risks of nicotine vaping in a more relevant and face-valid model compared to traditional whole-body nicotine vapor exposure in rodents.

Background: Nicotine is largely responsible for the initiation and maintenance of tobacco dependence and contributes to a global health problem. Aims: This study characterizes nicotine oral consumption and preference in male and female mice of several Diversity Outbred (DO) founder strains: C57BL/6J, A/J, 129S1/SvImJ, PWK/PhJ, NOD/ShiLtJ, and CAST/EiJ. It assesses the impact of nicotine concentration on intake and preference, the potential interaction of strain with sex, and estimates the degree of heritable variation in nicotine consumption. Methods: Two-bottle choice oral self-administration paradigm was used to assess nicotine intake, nicotine preference, and total fluid intake in male and female mice of each strain in a concentration-response manner. A conditioned place preference (CPP) test was performed to evaluate the rewarding and aversive effects of nicotine in certain strains after systemic administration of the drug. Results: The highest nicotine-consuming strain was found to be 129S1/SvlmJ, and the lowest nicotine-consuming strain was A/J. Strain differences in nicotine intake were not due to differences in bitter and sweet tastes as shown in the saccharine and quinine two-bottle choice tests. A/J strain showed no significant CPP for nicotine while the 129S1/SvImJ strain showed a significant CPP for nicotine and a higher preference when compared to the C57BL/6J strain. Heritability estimates of nicotine intake were sex dependent and concentration dependent. Conclusions: Data support that nicotine consumption patterns are heritable with an influence of genotype in a voluntary oral self-administration paradigm. Results pave the way for future studies with the highly recombinant DO mice that might lead to the identification of novel genetic loci and genes influencing nicotine consumption.

The use of menthol in tobacco products has been linked to an increased likelihood of developing nicotine dependence. The widespread use of menthol can be attributed to its unique sensory characteristics; however, emerging evidence suggests that menthol also alters sensitivity to nicotine through modulation of nicotinic acetylcholine receptors (nAChRs). Nicotinic subunits, such as β2 and α5, are of interest due to their implications in nicotine reward, reinforcement, intake regulation, and aversion. This study, therefore, examined the in vivo relevance of β2 and α5 nicotinic subunits on the pharmacological and behavioral effects of menthol. Data suggests that the α5 nicotinic subunit modulates menthol intake in mice. Overall, deletion or a reduction in function of the α5 subunit lessened aversion to menthol. α5 KO mice and mice possessing the humanized α5 SNP, a variant that confers a nicotine dependence phenotype in humans, demonstrated increased menthol intake compared to their WT counterparts and in a sex-related fashion for α5 SNP mice. We further reported that the modulatory effects of the α5 subunit do not extend to other aversive tastants like quinine, suggesting that deficits in α5* nAChR signaling may not abolish general sensitivity to the aversive effects of other noxious chemicals. Further probing into the role of α5 in other pharmacological properties of menthol revealed that the α5 subunit does not modulate the antinociceptive properties of menthol in mice and suggests that the in vivo differences observed are likely not due to the direct effects of menthol on α5-containing nAChRs in vitro.

Cigarette smoking remains a leading cause of preventable disease and death worldwide. Due to the devastating negative health effects of smoking, many users attempt to quit, but few are successful in the long-term. Thus, there is a critical need for novel therapeutic approaches. In these investigations, we sought to examine whether cannabidiol (CBD) has the potential to be repurposed as a nicotine cessation therapeutic. In the first study, male and female mice were trained to respond for intravenous nicotine infusions at either a low or moderate nicotine dose and then were pretreated with CBD prior to their drug-taking session. We found that CBD produced a significant decrease in the number of nicotine rewards earned, and this effect was evidenced across CBD doses and with both the low and moderate levels of nicotine intake. These effects on drug intake were not due to general motor-related effects, since mice self-administering food pellets did not alter their behavior with CBD administration. The potential effects of CBD in mitigating nicotine withdrawal symptoms were then investigated. We found that CBD attenuated the somatic signs of nicotine withdrawal and prevented nicotine's hyperalgesia-inducing effects. Taken together, these results demonstrate that modulation of cannabinoid signaling may be a viable therapeutic option as a smoking cessation aid.

Abstract ID 128020Poster Board 138Background: Smoking is linked to 1 in every 3 cancer deaths in the United States. Although cigarette smoking has decreased in recent years, electronic cigarette vaping has increased in popularity, especially among adolescents and young adults. The long-term effects of vaping and the risks for cancer are unknown and are of great interest. The objective of our research is to characterize a new e-cigarette vapor self-administration model and explore the impact of sex, nicotine concentration and age in adolescent and young adult mice to eventually study new mechanisms underlying nicotine dependence.Methods: Adolescent and young adult mice on a C57BL/6J (C57) background were used to characterize this new nicotine vaping model, analyzing vapor intake, locomotor activity, and somatic signs of withdrawal. Vapor intake was recorded for adolescent and adult C57 mice, and adult β2 nicotinic acetylcholine receptor (nAChR) knockout (KO) mice.Results: Male and female young adult C57 mice differed in their vaping intake of nicotine but both showed a dose-dependent increase in somatic signs of nicotine withdrawal after vaping cessation. Adolescent C57 mice are more resistant to the aversive doses of nicotine when compared to young adult mice. Adult β2 KO mice showed decreased intake for nicotine compared to wild type (WT).Conclusions: This model is reliable as a vaping self-administration model. Female C57 mice may be more sensitive to the rewarding properties of nicotine and adolescents may be more resistant to the aversive properties of nicotine. Future studies will look at potential new pharmacotherapies for smoking cessation.Extramural funding: This research was supported by the National Institute on Drug Abuse P30DA033934 and a pilot grant from the Virginia Youth Tobacco Projects (VYTP) Program.

BACKGROUND:As nicotine dependence represents a longstanding major public health issue, new nicotine cessation pharmacotherapies are needed. Administration of N-oleoyl glycine (OlGly), an endogenous lipid signaling molecule, prevents nicotine-induced conditioned place preference (CPP) through a peroxisome proliferator-activated receptor-alpha (PPARα) dependent mechanism, and also ameliorated withdrawal signs in nicotine-dependent mice. Pharmacological evidence suggests that the methylated analog of OlGly, N-oleoyl alanine (OlAla), has an increased duration of action and may offer translational benefit. Accordingly, OlAla was assessed in nicotine CPP and dependence assays as well as its pharmacokinetics compared to OlGly. METHODS:ICR female and male mice were tested in nicotine-induced CPP with and without the PPARα antagonist GW6471. OlAla was also assessed in nicotine-dependent mice following removal of nicotine minipumps: somatic withdrawal signs, thermal hyper-nociception and altered affective behavior (i.e., light/dark box). Finally, plasma and brain were collected after administration of OlGly or OlAla and analyzed by high-performance liquid chromatography tandem mass spectrometry. RESULTS:OlAla prevented nicotine-induced CPP, but this effect was not blocked by GW6471. OlAla attenuated somatic and affective nicotine withdrawal signs, but not thermal hyper-nociception in nicotine-dependent mice undergoing withdrawal. OlAla and OlGly showed similar time-courses in plasma and brain. CONCLUSIONS:The observation that both molecules showed similar pharmacokinetics argues against the notion that OlAla offers increased metabolic stability. Moreover, while these structurally similar lipids show efficacy in mouse models of reward and dependence, they reduce nicotine reward through distinct mechanisms.

Nicotine smoking contributes to many preventable disabilities, diseases and deaths. Targeting nicotine reward and withdrawal is a basis for the majority of smoking cessation pharmacotherapies. Due to the emergence of interest in 5-HT2A receptor modulators for numerous psychiatric disorders, we investigated the effect of nelotanserin, a 5-HT2A receptor inverse agonist, on nicotine reward and withdrawal in ICR mice. In nicotine-dependent mice, nelotanserin dose-dependently reduced somatic signs of nicotine withdrawal and thermal hyperalgesia as measured in the hot plate test. However, nelotanserin had no effect on anxiety-like behavior and failed to reduce nicotine reward as measured in the conditioned place preference test. Our results suggest that inverse agonism of the 5-HT2A receptor may be a feasible novel mechanism for smoking cessation by reducing both physical withdrawal and thermal hyperalgesia associated with nicotine abstinence but may require complementary pharmacotherapies targeting affective and reward-associated decrements to improve cessation outcomes.

Abstract ID 93521Poster Board 320Opioid use disorder (OUD) is a major health issue in the United States, with more than 100,000 opioid overdose deaths yearly. Treatments for OUD currently exist, but their efficacy is limited due to misuse potential, undesirable side effects, and low levels of compliance. Cross-sectional studies suggest that lifetime psilocybin use, a classical psychedelic drug, is associated with lower odds of OUD. Therefore, the current study sought to characterize the effects of psilocybin on different aspects of oxycodone, a widely used prescription opioid drug, withdrawal in mouse models. We evaluated the effect of psilocybin on oxycodone spontaneous withdrawal in mice. This study used 7-9 week-old C57BL/6J male and female mice who were surgically implanted with osmotic minipumps containing oxycodone (60 mg/kg/day) or saline for 7 days. Each treatment group was further injected with either saline or psilocybin (1 mg/kg ip) 2 hours following removal of minipumps. The next day, mice were evaluated for somatic signs of withdrawal and 7 days later for mechanical hypersensitivity. A separate cohort was also tested to determine the effect of psilocybin on oxycodone antinociceptive properties in the tail-withdrawal test. An additional cohort of serotonin (5-HT) 2A receptor knockout (KO) mice were tested in the same paradigm to determine the necessity of the 5-HT2A receptor, a receptor thought to be responsible for the “hallucinogenic” effects of psychedelics. Oxycodone male but not female mice that received psilocybin showed significantly less somatic signs of withdrawal. However, in both sexes, psilocybin reduced oxycodone withdrawal-induced mechanical hypersensitivity while not altering the antinociceptive effects of oxycodone. In addition, the reduction of somatic withdrawal signs by psilocybin was lost in the 5-HT2A KO male mice, however the reduction in withdrawal induced mechanical hypersensitivity remained in the KO mice of both sexes, implicating both 5-HT2A dependent and non-dependent reductions in withdrawal by psilocybin, respectively. Psilocybin shows promising potential for the treatment of opioid withdrawal. Future studies will determine the effect of psilocybin on the reinforcing properties of oxycodone in animals.Suoported by NIH P30 DA033934

Current treatments for chronic pain have low therapeutic efficacy, produce severe adverse effects or high abuse liability. There is a vital need to develop more efficacious and safer treatments for chronic pain. Currently, the analgesic effects of psychedelics are being explored in chronic pain conditions in clinical studies. Further preclinical and clinical research will improve our knowledge on the mechanisms and efficacy of these drugs and provide hope for neuropathic pain patients. In this study, we aim to investigate the effect of two classical psychedelics (DOI and psilocybin) in mouse models of paclitaxel-induced peripheral neuropathy (CIPN) and CFA chronic Inflammatory pain. Adult (M/F) C57BL/6J mice received paclitaxel every other day for a total of four injections (32 mg/kg, i.p.). On day 28 after paclitaxel, different cohorts of mice were injected with a single dose of DOI (0.3, 0.6, and 2 mg/kg, i.p.) or psilocybin (0.1, 0.3 and 1 mg/kg i.p.). Mechanical (von Frey) and cold (acetone) sensitivity tests were evaluated at different time points, up to 14 days. Psilocybin dose-dependently reversed mechanical and cold hypersensitivity for up to 14 days while DOI was effective only for 6 hours after the administration. A similar effect was seen in the CFA chronic inflammatory model. In addition, volinanserin, a selective 5-HT2A receptor antagonist, blocked the effect of psilocybin and DOI in these pain models. Our results suggest that activation of 5-HT2A receptors by various psychedelic drugs leads to an antinociceptive effect with different time-course efficacy in chronic pain models. This research was supported by the National Institute of Neurological Disorders and Stroke grant RNS127287 and the National Institute of Mental Health grant R01MH084894.

Opioid use disorder (OUD) is a serious health problem that may lead to physical dependence, in addition to affective disorders. Preclinical models are essential for studying the neurobiology of and developing pharmacotherapies to treat these problems. Historically, chronic morphine injections have most often been used to produce opioid-dependent animals, and withdrawal signs indicative of dependence were precipitated by administering an opioid antagonist. In the present studies, we have developed and validated a model of dependence on oxycodone (a widely prescribed opioid) during spontaneous withdrawal in male and female C57BL/6J mice. Dependence was induced by chronically administering oxycodone through osmotic minipumps at different doses for 7 days. Somatic withdrawal signs were measured after 3, 6, 24, and 48 h following minipump removal. Additionally, sensitivity to mechanical, thermal, and cold stimuli, along with anxiety-like behavior, were also measured. Our results indicated that spontaneous withdrawal following discontinuation of oxycodone produced an increase in total withdrawal signs after 60 and 120 mg/kg/day regimens of oxycodone administration. These signs were reversed by the administration of clinically approved medications for OUD. In general, both female and male mice showed similar profiles of somatic signs of spontaneous withdrawal. Spontaneous withdrawal also resulted in mechanical and cold hypersensitivity lasting for 24 and 14 days, respectively, and produced anxiety-like behaviors after 2 and 3 weeks following oxycodone removal. These results help validate a new model of oxycodone dependence, including the temporally distinct emergence of somatic, hyperalgesic, and anxiety-like behaviors, potentially useful for mechanistic and translational studies of opioid dependence.

Nicotine and tobacco-related deaths remains a leading cause of preventable death and disease in the United States. Several studies indicate that modulation of the endocannabinoid system, primarily of the endocannabinoid 2-Arachidonoylglycerol (2-AG), alters nicotinic dependence behaviors in rodents. This study, using transgenic knock-out (KO) mice, evaluated the role of the two 2-AG biosynthesis enzymes, (Diacylglycerol lipase-α) DAGL-α and DAGL-β in spontaneous nicotine withdrawal. DAGL-α deletion prevents somatic and affective signs of nicotine withdrawal, while DAGL-β deletion plays a role in hyperalgesia due to nicotine withdrawal. These results suggest a differential role of these enzymes in the various signs of nicotine withdrawal. Our behavioral findings relate to the distribution of these enzymes with DAGL-β being highly expressed in macrophages and DAGL-α in neurons. This study offers new potential targets for smoking cessation therapies.

Cannabis is among the most widely consumed psychoactive drugs around the world and cannabis use disorder (CUD) has no current approved pharmacological treatment. Nicotine and cannabis are commonly co-used which suggests there to be overlapping neurobiological actions supported primarily by the co-distribution of both receptor systems in the brain. There appears to be strong rationale to explore the role that nicotinic receptors play in cannabinoid dependence. Preclinical studies suggest that the ɑ7 nAChR subtype may play a role in modulating the reinforcing and discriminative stimulus effects of cannabinoids, while the ɑ4β2 * nAChR subtype may be involved in modulating the motor and sedative effects of cannabinoids. Preclinical and human genetic studies point towards a potential role of the ɑ5, ɑ3, and β4 nAChR subunits in CUD, while human GWAS studies strongly implicate the ɑ2 subunit as playing a role in CUD susceptibility. Clinical studies suggest that current smoking cessation agents, such as varenicline and bupropion, may also be beneficial in treating CUD, although more controlled studies are necessary. Additional behavioral, molecular, and mechanistic studies investigating the role of nAChR in the modulation of the pharmacological effects of cannabinoids are needed.