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. Author manuscript; available in PMC: 2022 Nov 1.
Published in final edited form as: Addict Biol. 2021 Feb 23;26(6):e13024. doi: 10.1111/adb.13024

Figure 2. Comparison of nicotine metabolite levels following passive vapor or intravenous nicotine self-administration (IVSA) in male rats.

Figure 2.

Blood samples were collected at baseline (pre-nicotine) or following 1 hr sessions of either nicotine vapor (5 mg/ml) or IVSA (0.03 mg/ml/infusion) from male rats. (A) Cotinine levels (n=8-16/group) were decreased with passive vapor exposure 30 min after the first session, as compared to IVSA subjects. However, these differences were not maintained at the later Day 1 time-point of 6 hr, or on Day 7 at the 30 min post-session time-point. *p<0.05 passive vapor vs. IVSA. (B) Male rats (n=8/group) exposed to nicotine vapor did not differ in their cotinine levels if placed in the chamber individually (single exposure) or with a cagemate (dual exposure) at all time-points assessed. (C) During the nicotine IVSA session (n=8), the rats self-administered a greater net amount of nicotine on Day 1 than on Day 7, which is consistent with the differences found in blood cotinine levels. *p<0.05 Day 1 vs. Day 7. (D) When IVSA nicotine intake was examined in 15-min intervals across the 1 hr session, it was found that the males exhibited a significant increase in responding only during the first 15 min interval, and thereafter, they maintained a consistent level of responding. *p<0.05 Day 1 vs. Day 7. Data are presented as mean ± SEM.