Estrogen increases arginine-vasopressin V1a receptor mRNA in the preoptic area of young but not of middle-aged female rats

We determined whether estrogen regulates the expression of arginine-vasopre ssin (AVP) receptor mRNA in the preoptic area (POA) of female rats. By reve rse transcription-polymerase chain reaction (PCR), we found that all three types of the AVP receptor mRNA, V1a, V1b and V2, were expressed in the POA, though the amount of PCR products was apparently different among them. In situ hybridization indicated that AVP V1a receptor mRNA was densely express ed in the POA, especially in the anteroventral periventricular nucleus of t he POA; in contrast, AVP V1b and V2 receptor mRNAs were not abundant in thi s area. Finally, we demonstrated by Northern blot that estrogen significant ly increased the expression of AVP V1a receptor mRNA in the POA of young ov ariectomized rats. However, this regulation by estrogen was lost in middle- aged rats, indicating an age-related impairment in the regulation of AVP V1 a receptor mRNA by estrogen in the POA. (C) 2000 Elsevier Science Ireland L td. All rights reserved.