Central nervous system control of pituitary XXXX receptors: evidence for involvement of multiple factors.

@entity398 @entity1640 @entity2819 @entity619 @entity134 @entity35 @entity6659
The regulation of pituitary @entity6659 ( @entity6659 ) receptor concentration was investigated in @entity35 with antero-lateral cuts (ALC) placed around the hypothalamus, as well as in Brattleboro homozygotes (HO) that genetically suffer from a lack of AVP. @entity1640 caused a reduction in (3H)-AVP binding, while counteracting the dramatic fall in binding that normally occurs after adrenalectomy. Surprisingly, in HO @entity35 , long-term adrenalectomy did cause pituitary AVP receptor number to decrease to an extent similar to that seen in normal @entity35 . However, the receptor disappeared twice as rapidly in heterozygote controls than in HO animals, with calculated half-lives of 1.1 and 2.0 days, respectively. In HO, chronic administration of @entity6659 reduced receptor concentration by about 80%, while the same dose of @entity398 (OT) produced only a 20-30% reduction. Whereas @entity619 injections did reverse the depressing effect of adrenalectomy on pituitary AVP receptors, they failed to enhance binding in sham-operated controls, treated or not with @entity6659 ; thereby suggesting a central site of action of the @entity134 . In contrast, in @entity35 with @entity1640 ALCs (i.e. with the pituitary lacking central control), @entity2819 implants did antagonize the reduction in receptor density caused by adrenalectomy. We conclude that the pituitary AVP receptor system lies mainly under control of the central nervous system, through a mechanism of action that not only seems to imply AVP and OT, but probably also some other @entity1640 factor(s). Glucocorticoids appear to exert a dual effect, acting indirectly through negative feedback control of neuropeptide release and, possibly, also directly on the pituitary to regulate binding sites.
