Figure 4.
Mathematical model of GnRH neuron calcium and electrical behavior. a, Schematic showing the key channels and pumps located in the ER and plasma membrane that comprise the model (see Materials and Methods for full description). b, Baseline behavior of the model showing the relationship between burst firing (top) and [Ca2+]i (bottom). The inset shows the structure of a typical burst. Subsequent panels show the effects of TTX (Inap and Inaf set to zero) (c) and 2-APB ([IP3] set to zero, SERCA pump set to 30% and Ca2+-ATPase set to 25%) (d). The precise effects of 2-APB on calcium pumps are not known, and thus these figures of 30 and 25% were chosen so as to obtain approximately the observed behavior. However, the results are not sensitive to the values chosen. e, Calcium free (Ical set to 40%; Icat set to 30%). Experimental data indicate that calcium entry is not completely eliminated by the calcium-free solution, although the precise extent to which calcium influx is decreased is not known. Again, the figures of 40 and 30% are chosen so as to obtain approximately the correct behavior, and the model is insensitive to the exact numbers used. f, Effect of CPA (SERCA set to zero) on firing and [Ca2+]i.