// singlecompartmen--an mimic nucleated patch to test properties of inserted soidum channel //------------------------------------------------------------------------ strdef neuron_name neuron_name = "scp" create soma soma { nseg = 10 diam = 10 L = 10 //-------------------Hou Han 081003 ------------------------------- // Notice that the time course of sodium channel depends on some external parameters, // like: // 1. celsius (global temperature, influences the most heavily on the time course as shown below) // since we check it with a singlecompartment model, properties of the cell should also be involved: // 2. cm (membrane capacity, the first term "cm * dV/dt" in HH equation, doesn't act on CHANNEL but on CELL) // Ideally, the term "dV/dt" should equal 0 in the V-clamp case (Hodgkin and Huxley,1952), // but however, NEURON treats all kinds of CLAMPs by a uniform method of solving the whole // HH equation without these simplifications, so the term "cm * dV/dt" could have a strong // effect on the time course of the membrane, as well as of the sodium channel. For example, // setting cm = 100 results in an obvious distortion of the soma.v(0.5) and soma.gna. // 3. Ra (intracellular resistance, little effect on the time course but a little on the amplitude) // Ra is crucial in those propagation cases, but here (single section, non-propagation case) it just controls // the "leakage" of channel current to the nearby cytoplasm. So its influence is limited. // // Paradoxically, in the NEURON environment which was designed for neurons rather than channels, it is // unavoidable that the properties of the "simglecompartment" which we put the channels in will influence // the properties of the channels which we really care about. So I suggest setting CM = 0 AND RA=INFINITE for the // exclusivity of the channels' properties which reflects the perfection of the mimic single-channel recording. // // ( Fortunately, however, the activation and the inactivation KINETICS are determined only // by the internal factors all defined in the .mod file. ) //----------------------------------------------------------------- //---------------------------Hou Han's --------------------------------- celsius=37 // TEMPERATURE is crucial whenever time course is concerned !! // near Line 129 of na.mod: " tadj = q10^((celsius - temp)/10) // mtau = 1/tadj/(a+b) " // Greg's tadj = 2.3^((37-23)/10)= 2.3^1.4 // default tadj = 2.3^((6.5-23)/10) =2.3^(-1.65) // difference in mtau = 2.3^3.05 = 12.7 times!! Ra=10000000000000000000000 // see the comments above cm=0 // see the comments above //------------------------------------------------------------------- //---------------------------Greg's------------------------ // celsius=37 // Ra=100 // cm=0.9 //--------------------------------------------------------- //----------- former settings of NEURON by default--------- // celsius=6.5 // Ra=35.4 // cm=1 //--------------------------------------------------------- } insert na16 insert na12 insert na