TABLE 1

IC₅₀ and maximum inhibition of nicotine-stimulated [³H]DA release for toxins used in this study

All subunits used to form receptors in oocytes were from rat clones. α6/α3β2β3 subtype is composed of an α6/α3 chimera, which contains the extracellular region of α6 and the remaining portion of the α3 subunit. α-MII is the only toxin that does not distinguish between α3^* and α6^* nAChRs. For each toxin, the IC₅₀ for [³H]DA release closely resembles that for inhibition of heterlogously expressed α6^* nAChRs. The substituted residues in the α-MII analogs are underlined.

Toxin	Sequence	IC₅₀ Oocytes			K_i α-MII Sites	IC₅₀ [³H]DA Release (95% CI)
		α3β2	α6/a3β2β3
		nM
α-MII	GCCSNPVCHLEHSNLC	2.18^a (1.2-3.8)	0.39^a (0.28-0.55)	0.22^a (0.20-0.25)	1.04 (0.47-2.3)	25 ± 1.8
α-MII[L15A]	GCCSNPVCHLEHSNAC	34.1^a (19-60)	0.92^a(0.65-1.3)	0.30^a (0.21-0.45)	0.84 (0.26-2.8)	22 ± 2.4
α-MII[H9A]	GCCSNPVCALEHSNLC	59^a (44-79)	0.79^a (0.56-1.1)	1.1^a (0.84-1.6)	1.25 (0.32-4.9)	21 ± 1.8
α-MII[E11A]	GCCSNPVCHLAHSNLC	8.7^a (6.8-11.1)	0.16^a (0.13-0.19)	0.27^a (0.19-0.37)	0.025 (0.010-0.061)	32 ± 3.5
α-PIA	RDPCCSNPVCTVHNPQIC	74.2^b (49-110)	0.95^b (0.71-1.3)	Not tested	1.48 (0.25-8.7)	26 ± 3.3

CI, confidence interval.
↵ a Taken from McIntosh et al. (2004).
↵ b Taken from Dowell et al. (2003).