REPEATED SODIUM DEPLETION AFFECTS GUSTATORY NEURAL RESPONSES IN THE NUCLEUS OF THE SOLITARY TRACT OF RATS

Furosemide sodium depletions were induced repeatedly to determine the effects on gustatory neural responses in the nucleus of the solitary t ract (NST) of chronically prepared, but lightly anesthetized, rats. So dium-replete and sodium-deplete conditions were alternated four times in each rat. When rats were under depleted conditions, the responses t o NaCl were significantly greater than in sodium-replete conditions. T his effect was attributable primarily to an increase in the magnitude of response of those neurons that responded better to NaCl than to the other standard stimuli (sucrose, citric acid, and quinine hydrochlori de). In addition, the largest change in responsiveness of the NaCl-bes t neurons occurred during the third and fourth sodium depletions. Thes e results are essentially opposite to those reported for NST neurons w hen sodium appetite is induced by dietary sodium restriction. This sug gests that the coding of intensity in the gustatory system is dependen t not only on the animal's deprivation condition, but also the method through which the deprivation is produced.