Milk-ejecting and antidiuretic activities under neurohypophyseal inhibition with alcohol and water overload

Antidiuretic activity was measured by determining free water clearance and urinary osmolality, controlled by glomerular filtration rate (Ccr) and solute excretion (Cosm). Milk-ejecting activity was assayed by recording intraductal mammary pressures. Baby's suckling was used as a stimulus to evoke milk ejection. Water overload (20 ml. per kilogram of body weight) and ethyl alcohol were used as inhibitors of the neurohypophyseal function. In subjects with water overload or blood alcohol concentrations between 50 and 100 mg. per 100 ml., inhibition of the antidiuretic activity without modifications of the milk ejection was observed. These results demonstrate that a differential inhibition of the gland was obtained, reinforcing our previous observations suggesting different neural pathways and/or mechanisms, controlling the release of oxytocin and antidiuretic hormone. On the contrary, blood alcohol concentrations over 200 mg. per 100 ml. were able to completely inhibit both activities, demonstrating that high doses of alcohol cannot be used to produce specific inhibition of oxytocin release.