Table 1.

Effective Dose of a Cigarette and Effective Concentration of Venous Plasma Nicotine Needed to Occupy 50% of α₄β₂* nAChRs During Positron Emission Tomography Scanning for the 3 Primary Regions of Interest^a

	No Correction (Cigarette)			With Correction (Cigarette)			With Correction (Plasma Nicotine Level)
	ED50, Cigarette	R, %	BP*	ED50, Cigarette	R, %	BP*	EC50, ng/mL	R, %	BP*
Thalamus	0.22 ± 0.11	61 ± 8	1.8	0.15 ± 0.05	67 ± 5	2.0	1.03 ± 0.26	71 ± 6	2.4
Brainstem	0.19 ± 0.07	64 ± 6	1.8	0.13 ± 0.03	67 ± 4	2.0	0.81 ± 0.27	70 ± 6	2.3
Cerebellum	0.16 ± 0.09	52 ± 7	1.1	0.11 ± 0.05	56 ± 5	1.3	0.73 ± 0.31	58 ± 6	1.4
Avg ± SD	0.19 ± 0.05			0.13 ± 0.03			0 87 ± 0.16

Abbreviations: 2-FA, 2-[18F]fluoro-3-(2(S)-azetidinylmethoxy) pyridine; Avg, weighted average for all 3 brain regions listed; BP*, binding potential, defined as the ratio VD_SB/VD_NDR, where VD_SB and VD_NDR are the volumes of distribution for specific binding and nondisplaceable radioactivity, respectively, calculated as R/(1-R); EC₅₀, effective concentration of venous plasma nicotine needed for 50% displacement of bound 2-FA; ED₅₀, effective dose of a cigarette needed for 50% displacement of bound 2-FA; nAChR, nicotinic acetylcholine receptor; R, maximum fractional displacement of the total radioactivity.

^aValues are expressed as mean ± SE unless otherwise indicated. Correction was based on an imperfect steady state of 2-FA observed after 3.5 hours for subjects scanned in the control (no smoking) condition, as described in the “Results” section, paragraphs 2 and 4.