Distribution of Antidiuretic Substance in the Diencephalon and Mesencephalon of the Dog

Antidiuretic (AD) activity was studied in the following regions of the dog brain: hypophysis (1); supraoptic and preoptic areas (2); medio-ventral hypothalamus (3); medio-dorsal hypothalamus and anterior thalamus (4); posterior thalamus (5); mammillary area (6); mesencephalon (7); temporal cortex (8); and caudate nuclei (9). AD activity was found in the samples derived from the hypophysis, hypothalamus, thalamus, and mesencephalon (brain region 1 to 7), while samples of the temporal cortex (8) and the caudate nuclei (9) showed no activity. The AD activity present in the hypophysis (1) and in ventral hypothalamic regions (2, 3 and 6) was due to the substance(s) whose activity was dependent upon an intact disulphide bond, mainly vasopressin. The AD activity in the thalamus (5) and in the mesencephalon (7) was only partially dependent on the vasopressin content.