Angiotensin- XXXX central interaction: localization and mechanism.

@entity172 @entity4998 @entity35 @entity1808 @entity4520
Intracerebroventricular (ICVT) administration of @entity4520 (EB) to ovariectomized female @entity35 decreased drinking and pressor responses to central injections of @entity1808 ( @entity1808 ). @entity172 treatment does not have this effect in male @entity35 . As EB given ICVT reaches many brain areas, the site of action of EB was localized using crystalline implants of EB in the medial preoptic area or the ventromedial nucleus of the hypothalamus. These areas were chosen as they have a high density of @entity172 receptors. Only medial preoptic area application of @entity172 decreased @entity1808 -induced drinking. Angiotensin receptor binding was examined in homogenates from different brain regions to determine if the mechanism through which @entity172 decreases central responses to @entity1808 involves altered receptor function. Systemic EB did not affect @entity1808 receptor binding in several brain regions but binding was decreased in homogenates from the preoptic area and septum-thalamus blocks which encompassed structures (median preoptic nucleus, organum vasculosum, and subfornical organ) implicated in central actions of @entity1808 . The sex specificity of the effect of @entity172 was dependent on @entity4998 . Manipulation of the neonatal hormone environment, which alters this brain differentiation, also altered the characteristic responses of the two sexes to @entity172 . Neonatal androgenization of females, which causes masculinization and defeminization, resulted in animals which as adults no longer responded to EB with decreased drinking. On the other hand, preventing the development of a male brain by neonatal castration produced animals which as adults tended to decrease their drinking following @entity172 . In summary, this study found that EB acts in the preoptic area to depress @entity1808 -induced responses by a site specific modulation of central @entity1808 receptors. Alteration of early brain development changed the responses of the two sexes to @entity172 , perhaps by altering sexual differentiation of the preoptic area.
