Table 3.

Kinetic parameters and least-squares fitting of macroscopic data

A Kinetic parameters	Units	NR1/NR2A	NR1/NR2B	% difference
10–90% rise time	ms	7.4 ± 0.7	11.6 ± 1.2	− 36*
Deactivation	ms	32.1	128	−75
τ1 (% area)		(94%)	(82%)
Deactivation	ms	202	799	−75
τ2 (% area)		(6%)	(18%)
Desensitization	ms	59.9	142	−58
τ1 (% area)		(38%)	(85%)
Desensitization	ms	257	888	−71

τ2 (% area)		(62%)	(15%)
B Fitted rate constants	Units	NR1/NR2A	NR1/NR2B	% difference
kd1+	s−1	85.1	550	−85
kd1−	s−1	29.7	81.4	−64
kd2+	s−1	230	112	105
kd2−	s−1	1.01	0.91	11
kon	μm−1 s−1	31.6	2.83	1017
koff	s−1	1010	38.1	2551
Kd	μm	32.0	13.5	137

A, 10–90% rise time measurements were made for individual patches (n = 18 for NR1/NR2A, n = 8 for NR1/NR2B; *P < 0.05). The deactivation or desensitization time course of mean waveforms was fitted to a double exponentially decaying function. B, fitting of macroscopic currents (see Fig. 5) to Scheme 4 with k_f+, k_f–, k_s+, k_s– fixed to values determined from single-channel data (Fig. 4 and Table 2) was used to determine binding and desensitization constants. K_d =k_off/k_on. Percentage difference is relative to the rate for the NR2B subunit. %diff = 100 × (2A–2B)/2B.