Rats chasing the dragon: A new heroin inhalation method.

Area of Science:

• Pharmacology
• Neuroscience
• Animal Models

Background:

• Human opioid use predominantly involves inhalation, yet rodent models primarily use injection or oral dosing.
• Existing electronic drug delivery systems (EDDS) for rodent heroin inhalation do not accurately replicate common human methods like direct vaporization.

Purpose of the Study:

• To establish a rodent model that accurately mimics the human inhalation method of heroin vaporization ('chasing the dragon').
• To assess the pharmacological effects and self-administration behaviors associated with inhaled heroin in rats.

Main Methods:

• Heroin hydrochloride powder was vaporized using a ceramic e-cigarette atomizer for inhalation exposure in middle-aged rats.
• Efficacy was evaluated using a warm water tail withdrawal assay for nociception, rectal temperature measurements, and operant self-administration paradigms.

Main Results:

• Inhaled vaporized heroin produced dose-dependent antinociceptive effects and increased rectal temperature in male rats.
• Antinociceptive effects in female rats were reversed by naloxone, confirming opioid receptor involvement.
• Female rats self-administered heroin vapor, increasing responding with higher reinforcement schedules and during extinction, indicating reinforcing properties.

Conclusions:

• Directly volatilized heroin inhalation successfully models heroin's typical effects in rats, comparable to EDDS.
• This novel method accurately replicates the 'chasing the dragon' inhalation technique, offering a valuable tool for long-term studies in aged rats.