Effects of dorsal, mediobasal and laterobasal septal lesions in the rat: Water and sodium chloride intake

Abstract

Under the conditions of a free choice between water and saline and with solid standard food ab lib., male rats with a lesion localized in the septum display a higher daily intake of NaCl than controls; the amount taken up represents the total NaCl taken in both saline and solid food. Rats with septal lesions have a higher total intake of liquids depending on experimental conditions and, in some cases, on the localization of the lesion. The consumption of water remains the same while the amount of the NaCl solution consumed increases. The molar concentration of the total NaCl consumption taken up with both the solution and the solid food, referred to the total fluid intake, is the same in control rats and in operated animals under all experimental conditions. The consumption of solid food by rats with septal lesions and, hence, the consumption of NaCl from the pellets, was increased depending on experimental conditions. The increase was observed in rats during the resting period, during the first application of fighting tests, and, in rats having the lesion in the laterobasal septal region, also during a repeated fighting period. The increased consumption of NaCl in rats with septal lesions reflects the fact that they drink more saline as compared with controls (by 86%). The increase in NaCl consumption due to solid food is only 24% as compared to controls. Mutual differences between septal rats with different localization of the lesion are only quantitative and depend on the conditions under which the animals are kept. Rats with lesion in the dorsal and mediobasal regions have a higher saline intake both when resting and exposed to a stimulation; the type of stimulation is of no importance in these animals. Rats with laterobasal lesion have a higher saline intake in the first stimulation period only. A hypothesis is discussed concerning the effect of septum on the appetite for NaCl.