A possible brain mechanism for rejection behavior to strong salt solution

Abstract

Rats accept about 1 per cent sodium chloride in larger quantity than any other concentrations and reject about 6 per cent sodium chloride. The preference and aversion behavior to salt solution were abolished after bilateral ablation of the cortical taste area. Daily intake of 1 per cent sodium chloride increased markedly after bilateral lesions of the ventromedial (VM) hypothalamus of the rat, and even 6 per cent sodium chloride was accepted a little. When the rat drunk 1 per cent sodium chloride, EEG of the lateral hypothalamus was activated, and EEG of the medial hypothalamus was activated by application of 6 per cent sodium chloride to the tongue. Evoked potentials from the medial hypothalamus, induced by electrical stimulation of the tongue, were abolished after ablation of the cortical taste area. Spontaneous unit discharges of the lateral part of the posterior hypothalamus were inhibited by application of 6 per cent sodium chloride to the tongue surface, while spontaneous unit discharges of the medial part of the posterior hypothalamus were activated when 6 per cent sodium chloride was applied to the tongue. A possible brain mechanism of the linguo-cerebro-hypothalamic system for aversion behavior to strong salt solution were discussed.