Thirst Tests in Dogs and Modifications of Thirst With Experimental Lesions of the Neurohypophysis

Abstract

Drinking was induced in dogs either by dehydrating the body to the extent of 5% of the wt. when they panted in a hot atmosphere, or by injecting 10 m[image] of NaCl/kg. of wt. In standard tests the amts. of water then drunk were modified by distention of the stomach with water (inhibition) or by injn. of Pitressin (enhancement). Urine flows and chloride concns., were measured in order to furnish further indexes of physiological states. Dogs in which exptl. diabetes insipidus was produced by hypothalamic injury, and others in which the pituitary stalk was sectioned without apparent diabetes insipidus, were subjected to the same tests. All of them drank excessive amts. of water in initial recovery from water deficit. After salt injn., only during subsequent hrs. was their drinking excessive. Their drinking was partially inhibited by gastric distention, but was not further enhanced by Pitressin admn. Thus in dogs with lesions of neurohypophysis an abnormality of drinking was identified that was independent of the processes of urinary excretion. Whether the role of the pituitary region be wholly nervous or partly endocrine, lesions of this region produced specific quantitative effects in drinking. Some other features of drinking were descr. that were not influenced by these lesions.