Inhibition of ad Libitum Feeding in Rats by Salt Injections and Water Deprivation

Inhibition of ad libitum feeding in rats was induced by hypertonic NaCl injections. Though osmotic loads of sufficient size were capable of abolishing feeding completely for a time, the effect was not as large as had been predicted from a hypothesis of strictly linear subtractive inhibition. Feeding at a low level of hunger seems to be somewhat less affected by osmotic inhibition than feeding on a deprivation schedule. Inhibition of feeding was also produced by deprivation of water, and both the inhibition of food intake during deprivation, and the disinhibition by subsequent drinking indicated that the amount of inhibition of food intake is a non-linear (accelerating) function of water deficit. A model of the process indicating that the thirst signal undergoes a non-linear transformation before being subtracted from the signal corresponding to food demand is proposed.