Table 1.

Rate constants for GluR1 and GluR4 channels

GluR1GluR4GluR1GluR4
α1-a3100 sec−18000 s−1δ01-g,1-h3.3 × 10−3 s−13.5 × 10−3
β1-a,1-b,1-j8000 s−120,000 s−1γ01-g,1-h,1-i1 s−16 s−1
k11-c,1-d2 × 107m−1/s−11 × 107m−1/s−1δ11-d,1-j1800 s−1800 s−1
k−11-c,1-d,1-e,1-f9000 s−110,000 s−1γ11-d,1-k7.6 s−145 s−1
k21-g910m−1/s−11000m−1/s−1δ21-d,1-e,1-l,1-m200 s−14000 s−1
k−21-g,1-k0.41 s−11 s−1γ21-l,1-m35 s−1220 s−1
  • The rate constants above refer to the kinetic model in Figure6a. Rate constants were estimated using ChannelLab by comparing currents or occupancies from Monte Carlo simulations with experimental data (reported here or published previously). The conductance values for the three open states were set to 9, 15, and 21 pS for GluR1 (Derkach et al., 1999; Banke et al., 2000; Irizarry, 2001) and 8, 16, and 24 pS for GluR4 (Swanson et al., 1997). The conductance of all other states was set to zero. All final simulations were performed with the rate constants above using 5000–20,000 channels. The experimental measurements or considerations that were the main constraints on the values of each rate constant are indicated by the superscript letters as follows.

  • F1-a Deactivation time constants, open time, and burst length distributions (Swanson et al., 1997; Derkach et al., 1999; Banke et al., 2000).

  • F1-b popenmeasurements (Smith and Howe, 2000; Robert et al., 2001).

  • F1-c Kinetics of entry into desensitization at low glutamate concentrations and the time-course of activation.

  • F1-d Concentration–response data for desensitization.

  • F1-e Concentration–response data for plateau currents.

  • F1-f Concentration–response data for peak currents.

  • F1-g Maximal recoveries from Hodgkin–Huxley fits.

  • F1-h Microscopic reversibility.

  • F1-i Rate of slow component of recovery.

  • F1-j Desensitization time constants.

  • F1-k Recovery time constants.

  • F1-l Relative amplitude of plateau and peak currents.

  • F1-m Recovery time-course at intermediate and high glutamate concentrations.