Effect of electrical and chemical stimulation of the lateral hypothalamus on taste preferences

Bipolar stainless steel electrodes or stainless steel cannulas were implanted stereotaxically into the lateral hypothalamus of rats. Drinking was elicited by electrical or chemical (carbachol or angiotensin II) stimulation of animals, which were offered water and solutions of sodium chloride, saccharin, acetic acid and quinine. During electrical stimulation, ingestion of water and of all the solutions increased significantly. The same rats ingested significantly more sodium chloride and saccharin solution after 23 h water deprivation and electrical stimulation of the lateral hypothalamus. Carbachol administered into the lateral hypothalamus induced ingestion of saccharin solution and water but not of sodium chloride. Angiotensin II injected into the lateral hypothalamus did not induce drinking in most of the rats and those which drank preferred sodium chloride, saccharin and water. Several of the rats which did not respond to angiotensin II injection into the lateral hypothalamus, 72 h after angiotensin II responded to injection of carbachol by drinking the saccharin solution. The results of electrical stimulation suggest that the lateral hypothalamus consists of neurons involved in the ingestion of primary taste solutions. Depending on the functional state of the organism, lateral hypothalamic stimulation modifies ingestion of other taste substances but not of salt, as indicated by water deprivation. Chemical stimulation indicates that the neurotransmitter responsible for salt intake is not cholinergic and that the cholinergic neurons evoke preference for sweet taste and water. It appears that angiotensin II is involved in salt intake, as well as in producing preference for sweet taste and water.