POSTERIOR PITUITARY-HORMONES IN THE CHICKEN AND HORSE - SIMILAR OR DIFFERENT ENDOCRINE FUNCTIONS

Neurohypophyseal hormones are produced in the hypothalamus but also oc cur in other organs such as the gonads. In the chicken, arginine-vasot ocin and mesotocin are the two neurohypophyseal hormones, while in the horse oxytocin and arginine vasopressin are found. Vasotocin in birds is responsible for functions equivalent to those exerted by oxytocin and vasopressin in mammals. Since common and diverging functions of ne urohypophyseal hormones are likely to exist in the chicken and the hor se, this paper aims to compare both species relative to reproduction, and milk ejection, water balance, plasma osmolality and exercise.