Acute nicotine administration reduces the efficacy of punishment in curbing remifentanil consumption in a seeking-taking chain schedule of reinforcement.

RATIONALE: Nicotine dependence is highly comorbid with opioid use disorders (OUDs). The use of nicotine-containing products increases the propensity to misuse prescription opioids and addressing both nicotine and opioid use simultaneously is more efficacious for treatment of OUDs than treating opioid use alone.

OBJECTIVES

Given this extreme comorbidity, further elucidation of the effects of nicotine as a factor in promoting vulnerability to development of OUDs is needed. Here, we sought to further explore the effects of nicotine administration on operant self-administration of remifentanil (RMF), a fast-acting synthetic µ-opioid receptor agonist, using a heterogenous seeking-taking chain schedule of reinforcement in unpunished and punished conditions.

METHODS

Male and female rats received nicotine (0.4 mg/kg) or saline prior to operant self-administration sessions. These sessions consisted of pressing a 'seeking' lever to gain access to a 'taking' lever that could be pressed for delivery of 3.2 µg/kg RMF. After acquisition, continued drug seeking/taking was punished through contingent delivery of foot-shock.

RESULTS

Nicotine, relative to saline, increased RMF consumption. Furthermore, nicotine treatment resulted in significantly higher seeking responses and cycles completed, and this effect became more pronounced during punished sessions as nicotine-treated rats suppressed RMF seeking significantly less than controls. Nicotine treatment functionally reduced the efficacy of foot-shock punishment as a deterrent of opioid-seeking.

CONCLUSIONS

Nicotine administration enhanced both appetitive and consummatory responding for RMF and engendered a punishment-insensitive phenotype for RMF that was less impacted by contingent administration of foot-shock punishment. These findings provide further support for the hypothesis that nicotine augments vulnerability for addiction-like behaviors for opioids.