Role of central vasopressin in cardiovascular regulation in rats

1. 大鼠脑血管加压素（AVP）受体亚型：为了确定脑内AVP受体亚型，我们检测了V1拮抗剂OPC-21268和V2拮抗剂OPC-31260对[^3H] -AVP特异性结合的抑制作用。[^3H] -AVP与大鼠海马膜的结合被V1拮抗剂OPC-21268强烈抑制。本研究采用逆转录聚合酶链反应（RT-PCR）方法检测成年大鼠海马AVP v1a和v2受体mrna。海马组织中检测到V2受体mRNA的PCR产物，但未检测到V1a受体mRNA的PCR产物。我们不知道为什么在本研究中没有在海马中检测到V1a受体mRNA。可能的解释是大脑中AVP受体mRNA的序列可能与外周组织中V1a受体mRNA的序列不完全一致。后叶加压素在压力感受器反射调节中的作用。我们研究了加压素及其受体在高血压压力受体反射敏感性中的作用。一肾一夹高血压大鼠初始期后脑区通过V2受体的压力感受器反射的敏感性显著升高，其他高血压模型均无明显升高。在此期间，V2受体mRNA在脑后区短暂表达。提示后脑区加压素在压力感受器反射和一类高血压的发生中起重要作用。

1. Vasopressin (AVP) receptor subtypes in rat brain :To determine the subtype (s) of the AVP receptor in the brain, we examined the inhibitions of specific binding of [^3H] -AVP by the V1 antagonist OPC-21268 and V2 antagonist OPC-31260. [^3H] -AVP binding to rat hippocampal membranes was strongly inhibited by the V1 antagonist, OPC-21268. In this study, we tested for AVP V1a-and V2-receptor mRNAs in the hippocampus of adult rats by a reverse transcription-polymerase chain reaction (RT-PCR) method. PCR product of the V2 receptor mRNA was detected in the hippocampus, but that of V1a receptor mRNA was not. We do not know why V1a receptor mRNA was not detected in the hippocampus in this study. Possible explanations are that the sequence of the AVP receptor mRNA in the brain may not completely consistent with that of V1a receptor mRNA in peripheral tissues.2.Role of vasopressin in the area postrema in regulation of baroreceptor reflex.We examined the involvements of vasopressin and its receptors in the sensitivity of the baroreceptor reflex in hypertension. The sensitivity of baroreceptor reflex was remarkably increased via V2 receptor in the area postrema in the initial stage of one-kidney, one clip hypertensive rats, but not in the other hypertensive models. And this period, V2 receptor mRNA was expressed temporarily at the area postrema. These results suggested that vasopressin in the area postrema have very important roles of baroreceptor reflex and development of a kind of hypertension.