A Nonlinear Time-Varying Mathematical Analog of the Gluco-Corticoid Control

The basic characteristics contributing to the nonlinear time-varying gluco-corticoid control mechanism in 300-gram male rats fasted 18 hours have been formulated. Intact animal time responses of the plasma levels of corticosterone to intraperitoneally injected doses of 50, 200, and 500 μg/kg simulated on an analog computer were compared with the experimental results. Nonlinear time-dependent characteristics of the hypothalamic-hypophyseal complex, previously unobtainable experimentally, were arrived at indirectly through the use of experimental data and simple control theory analysis. Involved compartmental analysis of the complex kinetics for the intraperitoneally injected dose was bypassed by using experimental data and concepts of control mechanisms. The model was found to be compatible with the linear model of Yates.