Understanding sex differences and the translational value of models of persistent substance use despite negative consequences.

Persistent substance use despite negative consequences is a key facet of substance use disorder. The last decade has seen the preclinical field adopt the use of punishment to model adverse consequences associated with substance use. This has largely involved the pairing of drug use with either electric foot shock or quinine, a bitter tastant. Whilst at face value, these punishers may model aspects of the physical and psychological consequences of substance use, such models are yet to assist the development of approved medications for treatment. This review discusses progress made with animal models of punishment to understand the behavioral consequences of persistent substance use despite negative consequences. We highlight the importance of examining sex differences, especially when the behavioral response to punishment changes following drug exposure. Finally, we critique the translational value these models provide for the substance use disorder field.

Sex Differences in Alcohol Use: Is It All About Hormones?

Risky alcohol use and alcohol use disorders (AUD) are a rising problem in women, yet a major disparity in our understanding of what drives alcohol consumption in women remains. Historically biomedical research has focused on male subjects; however, recent increases in reporting of females, have highlighted major differences between the sexes. Here we review the current literature of the effect of gonadal steroid hormones (estrogens, androgens, and progestins), neurosteriods, and neurobiological factors on alcohol use in clinical and preclinical studies of both sexes. Further, we briefly discuss how fundamental sex differences in genetics, metabolism, neuroimmune, and stress responses may influence sex differences in alcohol intake. Comparing the sexes could aid in the discovery of novel therapeutics to treat AUD, and implementation of current treatment options in women.

A model of emotional stress-induced binge eating in female mice with no history of food restriction.

Overeating is a major contributing factor to obesity and related health complications. For women, in particular, negative emotions such as stress strongly influence eating behavior and bingeing episodes. Modeling this type of binge eating in rodents presents challenges: firstly, stress-induced anorexia is commonly observed in rodents therefore a mild stressor is required in order to observe an orexigenic effect. Second, many studies report using calorie restriction to observe the required behavior; yet this does not necessarily reflect the human condition. Thus, the aim of this study was to develop a model of emotional stress-induced bingeing independent of caloric restriction. Female and male C57BL/6J mice were divided into ad libitum (n = 20 per sex) and food-restricted (n = 20 per sex) groups which were both further split into a control group and a group exposed to frustration stress (n = 10 per group). All mice were provided intermittent access to a highly palatable food in 2 cycles. At the end of each cycle the stress group was subjected to a 15-minute frustration episode where highly palatable food was within the home cage but inaccessible. Both groups were then given free access for 15 minutes. Frustrated female mice from the ad libitum displayed binge-like behavior compared with controls (P = .0001). Notably, this behavior was absent in males. Ovariectomy had no impact on binge-like behavior. Collectively, these data validate a novel model of emotional stress-induced binge eating specific to female mice which does not require caloric restriction and is not driven by ovarian hormones.

Contribution of dopaminergic and noradrenergic systems in the antinociceptive effect of α-(phenylalanyl) acetophenone.

BACKGROUND: This study evaluated the antinociceptive action of α-(phenylalanyl) acetophenone (PSAP) in mice. METHODS: Evaluated whether the serotonergic, adrenergic and dopaminergic systems are involved in PSAP antinociceptive activity. PSAP was administered intragastrically (ig) 30min prior to formalin or glutamate test and compared with a standard drug, meloxicam (10mg/kg, ig). RESULTS: The treatment with PSAP (10-50mg/kg) caused inhibition in the neurogenic phase and reduced the paw oedema caused by intraplantar (ipl) injection of formalin. PSAP (1-50mg/kg) decreased the nociceptive response in the inflammatory phase of the formalin test and in licking behaviour triggered by glutamate at doses of 0.1-50mg/kg. The antinociceptive effect of PSAP (1mg/kg) was abolished when the animals were pre-treated with prazosin (α1-adrenergic antagonist receptor, 0.15mg/kg, intraperitoneally, ip), yohimbine (α2-adrenergic antagonist receptor, 1mg/kg, ip) and sulpiride (D2/D3 dopamine antagonist, 5mg/kg, ip). The antinociceptive effect of PSAP (1mg/kg) was not abolished by WAY100635 (5-HT1A-selective serotoninergic antagonist, 0.7mg/kg, ip), ketanserin (selective antagonist of serotonergic 5-HT2A/2C, 0.3mg/kg, ip), ondansetron (5-HT3 selective serotoninergic antagonist, 0.5mg/kg, ip) or SCH23390 (D1 dopamine receptor antagonist, 0.05mg/kg, ip) in the glutamate test. No changes in locomotor activity were observed in the animals treated with PSAP and/or antagonists in the open field test. CONCLUSION: These results showed the antinociceptive action of PSAP in formalin and glutamate tests and the involvement of the dopaminergic and adrenergic systems in its antinociceptive activity.