Immunoreactive arginine-vasopressin in Brattleboro rat ovary

Homozygous (di/di) Brattleboro rats have normal hypothalamic levels of oxytocin and neurophysin I, but undetectable levels of neurophysin II and arginine-vasopressin (AVP)1. This defect has been presumed to be at the genomic or transcriptional level, as AVP messenger is reported to be drastically reduced, if not absent, from the hypothalamus of Brattleboro rats2. Recent studies suggest de novo production of various neuropeptides in the mammalian gonad3–7, including AVP7. We report here the detection and localization of immunoreactive (ir) AVP in the luteal cells of adult homozygous Brattleboro rats, and the modulation of this ovarian ir-AVP by gonadotropins. These findings are thus consistent with a tissue-specific defect of AVP expression in the magnocellular neurones of the Brattleboro rat, and suggest that a comparable defect does not occur in the ovaries of such animals.