Computer simulation of thirst and water balance

The body water, alimentary exchange, renal control, and drinking sub-systems involved in water regulation in the rat were simulated using a digital computer. For each subsystem, coefficients and time constants were fitted to published data, and the calculations closely followed a physiological understanding of the mechanisms in question. Experimental data were then obtained for the drinking and renal response to injections and continuous infusions of hypertonic saline in rats, and the overall performance of the model was tested by comparing its response to these experimental results. Agreement was good for these and other results, indicating that the model adquately takes account of the major variables in the regulation of body water. Manipulations of the model and comparisons with rats indicate the necessity for short term oral and gastric feedback, and for a thirst threshold