Sodium chloride intake following electrochemical stimulation of the frontal lobe cortex in the rat

The effect of stimulation of the medial surface of the cerebral cortex on the intake of sodium chloride (NaCl) solution was studied in male rats which were depleted of sodium by peritoneal dialysis (p.d.). Electrochemical stimulation (anodic d.c.) was applied through monopolar stainless-steel electrodes chronically implanted in the unanaesthetized freely-behaving animal. Stimulation (100 microA/30 sec,) of the anterior cingulate cortex in its dorsal and ventral portions, 24 hr after p.d. decreased NaCl intake by about 30% compared with pre-stimulation intake in the same animal. An opposite behavior was observed after electrochemical stimulation of the superficial layers of the pre-limbic area. A significant sodium intake occurred when the stimulus was applied 5 hr after p.d. at a time when the sodium appetite was still not evident. However, stimulation applied 24 hr after p.d. gave no significant difference from control. The degree of stimulation exerted by the pre-limbic area on NaCl intake was proportional to the amount of current applied. The results of the present study indicate that the frontal lobe cortex of the brain has a dual effect on the preference for sodium intake in sodium depleted rats, with the cingulate area being inhibitory and the pre-limbic area being facilitatory.