Vasopressin and vasopressin-antagonists applied to neonatal Wistar rats: effects on body and brain development and water metabolism.

Neonatal Wistar rats were continuously treated with the vasopressin-antagonists d(CH2)5[Tyr(Me)2]AVP, d(CH2)5DAVP or d(CH2)5[D-Ile2,Ala4]AVP, which have high anti-vasopressor or anti-anti-diuretic activity. The treatments were performed to test the hypothesis that arginine-vasopressin (AVP) might have a stimulatory effect on brain development, which is based upon the disturbed brain development of the AVP-deficient Brattleboro rat. None of the treatments with antagonists, either being given via a small drug-delivery device or by twice daily injections, inhibited body or brain development, though d(CH2)5[Tyr(Me)2]AVP treatment even had some stimulatory effect on cerebellar weight as measured at one month of age. Similar drug-delivery treatment with AVP or oxytocin (OX), or injections with 250 ng AVP, lysine-vasopressin (LVP), arginine-vasotocin (AVT) or OX had no stimulatory developmental effect. However injections with 2.5 micrograms of these peptides reduced body development, albeit transiently, of the neonatal Wistar rats. Moreover in this latter group not only the known lasting effects of AVP and LVP on body water metabolism were seen but also such effects were present after AVT and OX treatment.