PT  - JOURNAL ARTICLE
AU  - Arnold Gutierrez
AU  - Jacques D. Nguyen
AU  - Kevin M. Creehan
AU  - Michael A. Taffe
TI  - Female rats self-administer heroin by vapor inhalation
AID  - 10.1101/2020.03.30.016725
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.03.30.016725
4099  - http://biorxiv.org/content/early/2020/10/14/2020.03.30.016725.short
4100  - http://biorxiv.org/content/early/2020/10/14/2020.03.30.016725.full
AB  - Over the last two decades the United States has experienced a significant increase in the medical and non-medical use of opioid drugs, resulting in record numbers of opioid-related overdoses and deaths. There was an initial increase in non-medical use of prescription opioids around 2002, followed later by increased heroin use and then most recently fentanyl. Inhalation is a common route of administration for opioids, with a documented history spanning back to Mediterranean antiquity and up through modern use with e-cigarette devices. Unfortunately, preclinical studies using inhalation as the route of administration remain relatively few. This study was conducted to determine the efficacy of e-cigarette vapor inhalation of heroin in rats. Non-contingent exposure to heroin or methadone vapor produced anti-nociceptive efficacy in male and female rats. Female rats were trained to self-administer heroin vapor; the most-preferring half of the distribution obtained more vapor reinforcers when the concentration of heroin was reduced in the vapor vehicle and when pre-treated with the opioid receptor antagonist naloxone. The anti-nociceptive effect of heroin self-administered by vapor was identical in magnitude to that produced by intravenous self-administration. Finally, anxiety-like behavior increased 24-48 hours after last heroin vapor access, consistent with withdrawal signs observed after intravenous self-administration. In sum, these studies show that rewarding and anti-nociceptive effects of heroin are produced in rats by vapor inhalation using e-cigarette technology. Importantly, self-administration models by this route can be deployed to determine health effects of inhaled heroin or other opioids.Competing Interest StatementThe authors have declared no competing interest.