EFFECT OF OXYTOCIN AND ADRENERGIC DRUGS ON BOVINE REPRODUCTION

Abstract

ABSTRACT Oxytocin (100 U.S.P. Units) injected into cows from Day 3 through 6 post-oestrum caused short oestrous cycles (8.7 days). When superimposed on oxytocin treatment, norepinephrine (6–10 μg/kg) inhibited the oestrous cycle shortening effect of oxytocin (16.8 days), while isoproterenol (3 μg/kg) was ineffective (11.3 days). The concentration of progesterone in jugular vein blood on Day 4 through 8 post-oestrum was determined by gas-liquid chromatography. Progesterone levels on Day 4 through 6 post-oestrum, regardless of treatment, were not significantly different (P > 0.05). On Day 7, progesterone decreased significantly in the oxytocin and oxytocin + isoproterenol groups; in animals treated with oxytocin + norepinephrine the progesterone concentration increased significantly over other means (P < 0.01). These data support the idea that norepinephrine, an alpha adrenergic stimulant, inhibits the luteolytic action of oxytocin and isoproterenol, a beta adrenergic stimulant, is ineffective.