SEPTAL AND HIPPOCAMPAL RELEASE OF VASOPRESSIN AND OXYTOCIN DURING LATE PREGNANCY AND PARTURITION IN THE RAT

The push-pull perfusion technique, in conjunction with specific radioimmunoassays, was used to monitor the release of both arginine vasopressin (AVP) and oxytocin (OXT) within distinct limbic brain areas of conscious female rats. In pregnant rats near term, the release of AVP was greater than that of virgin rats in both the ventral (p < 0.001) and mediolateral (p < 0.001) septal areas; similarly, release of OXT increased in the ventral septal area (p < 0.01) at this time. In contrast, no changes in the levels of either peptide occurred in the dorsal hippocampus. In parturient rats, AVP release tended to decrease in the septal areas but increased fivefold in the dorsal hippocampus (p < 0.001) compared to pregnant animals. In contrast, OXT levels assayed in the same perfusates did not differ from those observed in pregnant animals. Plasma levels of AVP in pregnant rats (p < 0.05) and of OXT in parturient animals (p < 0.01) were found to be increased over levels in virgin rats. The regionally different and peptide-specific changes in release pattern of AVP and OXT in virgin, pregnant parturient rats may be of physiological significance in antipyresis and behaviors accompanying parturition.