Table 1

The effect of physostigmine depends on the subunit stoichiometry

Subunits injected	Response to 1 mM ACh			ACh EC₅₀			Response to physostigmine
	Mean ± S.E.	No. of Cells	P value ^{^a}	Mean ± S.E.	No. of Cells	P value ^{^a}	Mean ± S.E.	No. of Cells	P value ^{^b}
	nA			μM
α&β 8:1	–13042 ± 1303	51	–	132 ± 10	33	–	1.42 ± 0.04	38	–, <0.001
α–β&α	–7238 ± 1179	68	0.004	78 ± 5	47	<0.001	1.51 ± 0.08	25	0.3, <0.001
β–α&α	–14421 ± 1081	94	0.6	121 ± 10	59	0.6	1.38 ± 0.03	51	0.7, <0.001
α&β 1:8	–1029 ± 193	47	–	4.5 ± 0.6	20	–	0.69 ± 0.03	15	–, <0.001
α–β&β	–341 ± 98	32	0.01	2.9 ± 0.5	14	0.3	0.78 ± 0.07	10	0.6, 0.01
β–α&β	–1007 ± 116	91	1.0	3.7 ± 0.5	57	0.5	0.72 ± 0.05	28	0.9, <0.001
α–β	–761 ± 136	45		90 ± 11	30		1.02 ± 0.05	19	–,0.7
β–α	–4837 ± 738	88		105 ± 12	55		1.00 ± 0.07	23	–, 1.0

Subunits are shown by the combination injected; for example, α&β 8:1 indicates that free subunits were injected at a ratio of 8:1::α4:β2, whereas α–β&α indicates that the α4–β2 dimer was injected with a free α4 subunit (1:1 ratio). Means ± S.E. and the number of cells are presented for the response to 1 mM ACh, for the concentration of ACh producing a half–maximal response (EC₅₀) and for the ratio of the response to a low concentration of ACh in the presence of physostigmine to the response of the same cell to ACh in the absence of physostigmine. Data for dimers injected in the absence of a free subunit are given in the last two rows, for comparison. Note that responses can be seen when dimers alone are injected, but the pharmacology of the responses differs from that seen when a free subunit is also injected demonstrating the presence of the free subunit in the pentamers (see also Jin and Steinbach, 2011). Dashes indicate that that particular subunit combination was the comparison value for the P computation.
↵^a P values give the significance of the difference in value to that of the first entry in the set (one–way analysis of variance with Dunnett correction).
↵^b The first P value is the significance of the difference to the first entry in the set, whereas the second value is the difference of the potentiation to a value of 1 (i.e., no effect; one–sample t test). Dashes indicate that that particular subunit combination was the comparison value for the P computation.