Estrogen-progesterone (EP) treated adult male rats were injected intravenously (iv) with 0.1, 1 or 10 μg arginine vasotocin (AVT) or Ringers lactate solution. A significant dose-related rise in plasma prolactin was evident 10 min after injection with AVT. In a second experiment, shamoperated or pinealectomized EP-treated male rats were injected iv with 0.1 or 1 μg AVT or diluent. Plasma prolactin was significantly elevated in both sham-operated and pinealectomized groups at both 10 and 20 min post-injection of 1 μg AVT. These results indicate that AVT has prolactin-releasing activity and that this activity is not dependent upon the presence of an intact pineal gland.
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