Abstract
Enteramine (5 hydroxytryptamine) decreases the urine volume of hydrated dogs at doses which do not stimulate the smooth muscle and do not modify the systemic blood pressure. The lower doses (0, 1-0, 3 mg./kilo) subcut. or intraven. decrease the urine volume without affecting the GFR, while higher doses reduce also the filtration rate; both lower and higher doses increase the RPF. The above described expts. suggest that the anti-diuretic effect of enteramine in the dog derives principally from an increased reabsorption of water from the renal tubule.