The collective effect of non-nicotine constituents on the reinforcing and neuropharmacological effects of comprehensive cigarette smoke and electronic nicotine delivery system (ENDS) aerosol extracts in rats.
Tobacco product extracts containing nicotine and non-nicotine constituents are useful for understanding the collective role of these constituents in tobacco use disorder (TUD). However, few studies have used extracts with both water-soluble and non-water-soluble constituents with accompanying chemical analysis, or compared behavioral and neuropharmacological effects across product types. To address these limitations, we compared the relative abuse liability of cigarette smoke (CS) and electronic nicotine delivery system (ENDS) aerosol (EA) extracts to nicotine alone using intravenous self-administration in rats, and examined effects on nucleus accumbens (NAc) dopamine (DA) release and binding/function at nicotinic acetylcholine receptors (nAChRs) and other addiction-related receptors in vitro. CS extract contained higher levels of several behaviorally active non-nicotine constituents than EA extract. Both extracts produced a downward/leftward shift in the descending limb of the unit dose-response curve relative to nicotine alone, while only CS extract produced greater compensatory increases in responding compared to nicotine alone. Demand intensity (Q0) was lower for CS but not EA extract, relative to nicotine alone, whereas demand elasticity for both extracts was similar to nicotine alone. Stress-induced reinstatement was comparable between CS extract and nicotine alone but attenuated for EA extract. CS extract, but not EA extract, showed greater potency for 4{beta}2 nAChR activation and substantial binding across numerous non-nAChRs (DA, serotonergic, opioid) relative to nicotine alone at a high screening concentration. CS extract, but not nicotine alone, also inhibited cyclooxygenase (COX)-1 and -2 at smoking-relevant concentrations. There was no difference in NAc DA release between formulations. These findings indicate non-nicotine constituents contribute to certain reinforcing and neuropharmacological effects of CS, and to a lesser extent EA. Our finding of COX inhibition by CS extract warrants further investigation as a potential mechanism contributing to the effects of CS and TUD.