LEVELS OF ARGININE-VASOPRESSIN AND OXYTOCIN IN THE PITUITARY GLAND AND INDIVIDUAL HYPOTHALAMIC NUCLEI OF THE GENETICALLY OBESE ZUCKER RAT

Abstract Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, Maryland 20014, U.S.A. and *Department of Medicine, Ohio State University, College of Medicine, Columbus, Ohio, U.S.A. (Received 20 September 1977) The genetically obese Zucker rat exhibits several endocrine disorders, including defects of the female reproductive system such as delayed puberty, irregular oestrous cycles, failure to mate and refractoriness to pseudopregnancy-inducing stimuli (Saiduddin, Bray, York & Swerdloff, 1973). Zucker rats show hyperdipsia, increased plasma osmolality and excrete a large volume of urine with a decreased osmolality and an increased protein content, suggesting a deficiency in the regulation of body fluids (York & Bray, 1971, 1973; Bray, York & Swerdloff, 1973). These considerations, plus the recent findings that in Zucker rats the concentration of noradrenaline is reduced in the hypothalamic paraventricular nucleus and increased in the median eminence (Cruce, Thoa & Jacobowitz, 1976), prompted us to measure levels of arginine-vasopressin (AVP) and