Table 2

Relative affinity (K_i) estimates for anabaseine, anabasine and nicotine on different vertebrate nicotinic receptors, expressed in terms of the active monocationic species

Receptor Type	K_i ± S.E. (μM)
Receptor Type	Anabaseine	Nicotine	Anabasine
Skeletal muscle^2-a (Fish)	0.21 ± 0.12	1.4 ± 0.12	7.2 ± 0.88
Alpha7^2-b (Rat)	0.058 ± 0.007	0.40 ± 0.035	0.058 ± 0.027
Alpha4-Beta2^2-c (Rat)	0.032 ± 0.004	0.0041 ± 0.001	0.26 ± 0.059

All three binding assays were done at pH 7.4, where the monocationic concentrations were: anabaseine, 29% of total; nicotine, 76% of total; anabasine, 95% of total.
↵2-a Torpedo electric organ values are IC₅₀s, since inhibition of the rate of irreversible binding of¹²⁵I-BTX was measured.
↵2-b K_is were determined from monocationic IC₅₀s (fig. 10) using a ¹²⁵I-BTXK_i of 0.4 nM, calculated from a Scatchard plot (data not shown).
↵2-c K_is were determined from monocationic IC₅₀s (fig. 12) using a ³H-MCC K_i of 11 nM obtained from the data shown in figure 11.