Impact of tobacco smoke constituents on nicotine-seeking behavior in adolescent and adult male rats.

Introduction: Given the rapid increase in teen vaping over recent years it is critical to understand mechanisms underlying addiction and relapse to tobacco use at this age. To evaluate the role of non-nicotine constituents in cigarette smoke, our lab has previously established a model of intravenous self-administration of aqueous cigarette smoke extract (CSE). We now compare the sensitivity of male adolescent and adult rats who have self-administered CSE or nicotine to reinstatement with the pharmacological stressor, yohimbine, with and without cues. Methods: Adolescents and adults, aged postnatal day (P) 34 and 84, were tested for the effect of yohimbine (0-2.5 mg/kg) on plasma corticosterone levels to establish a dose that was an effective stressor at both ages. Separate groups of animals were trained to lever press for food before beginning 1-hour drug self-administration sessions for nicotine or CSE (15 µg/kg/infusion nicotine content). Once stable responding was reached, drug was removed, and behavior extinguished. Drug-seeking behavior was reinstated with yohimbine, cues, or a combination of yohimbine and cues. Results: Although adolescents and adults showed different dose-responses for yohimbine-induced corticosterone release, a dose of 2.5 mg/kg increased stress hormone levels at both ages. Whereas both ages displayed similar responding for CSE and nicotine, adolescents self-administered more CSE and nicotine as compared to adults. Cues and cues + stress reinstated responding to a greater extent in animals that had self-administered CSE, regardless of age. Discussion: These findings suggest that non-nicotine tobacco smoke constituents influence later but not earlier stages of addiction in both adolescent and adult male rats.

Cigarette Smoke Extract: A Preclinical Model of Tobacco Dependence.

Animal models are used to study many human diseases, one of which is tobacco addiction. Most preclinical models use nicotine alone, although there are >7000 constituents present in tobacco smoke. The clinical literature suggests that cigarettes have a strong addictive potential, which is not paralleled in preclinical studies using nicotine alone. In order to address the gap between clinical and preclinical literature on tobacco dependence, cigarette smoke extracts containing tobacco constituents have been developed. This unit describes a procedure for producing an aqueous cigarette smoke extract (CSE) which animals readily self-administer. In addition, we describe how to make the apparatus for producing CSE and how to analyze the solution for nicotine content. © 2016 by John Wiley & Sons, Inc.

Self-administration of nicotine and cigarette smoke extract in adolescent and adult rats.

Although smoking initiation typically occurs during adolescence, most preclinical studies of tobacco use involve adult animals. Furthermore, their focus is largely on nicotine alone, even though cigarette smoke contains thousands of constituents. The present study therefore aimed to determine whether aqueous constituents in cigarette smoke affect acquisition of nicotine self-administration during adolescence in rats. Adolescent and adult male rats, aged postnatal day (P) 25 and 85, respectively, were food trained on a fixed ratio 1 (FR1) schedule, then allowed to self-administer one of 5 doses of nicotine (0, 3.75, 7.5, 15, or 30 µg/kg) or aqueous cigarette smoke extract (CSE) with equivalent nicotine content. Three progressively more difficult schedules of reinforcement, FR1, FR2, and FR5, were used. Both adolescent and adult rats acquired self-administration of nicotine and CSE. Nicotine and CSE similarly increased non-reinforced responding in adolescents, leading to enhanced overall drug intake as compared to adults. When data were corrected for age-dependent alterations in non-reinforced responding, adolescents responded more for low doses of nicotine and CSE than adults at the FR1 reinforcement schedule. No differences in adolescent responding for the two drugs were seen at this schedule, whereas adults had fewer responses for CSE than for nicotine. However, when the reinforcement schedule was increased to FR5, animals dose-dependently self-administered both nicotine and CSE, but no drug or age differences were observed. These data suggest that non-nicotine tobacco smoke constituents do not influence the reinforcing effect of nicotine in adolescents.

Cell-free expression of functional receptor tyrosine kinases.

Receptor tyrosine kinases (RTKs) play critical roles in physiological and pathological processes, and are important anticancer drug targets. In vitro mechanistic and drug discovery studies of full-length RTKs require protein that is both fully functional and free from contaminating proteins. Here we describe a rapid cell-free and detergent-free co-translation method for producing full-length and functional ERBB2 and EGFR receptor tyrosine kinases supported by water-soluble apolipoprotein A-I based nanolipoprotein particles.