title: Evidence that inhibition of medial preoptic dopaminergic activity may be involved in the prepubertal desensitization to the negative oestrogen feedback in female rats.
abstract: Immature female rats were bilaterally lesioned in the medial preoptic area (MPOA) or hypothalamic ventromedial-arcuate region (VMAR) at 21 days of age and daily injected with the dopamine (DA) agonist bromocriptine (CB-154) through day 26. Estimation of the serum LH and FSH concentrations following ovariectomy and two injections of 0.05 micrograms oestradiol benzoate (OB)/100 g b.w. revealed that the desensitization to the negative feedback effect of OB induced by lesioning of the MPOA was almost completely prevented by CB-154. A similar effect of the drug was not found in rats lesioned in the VMAR. The DA antagonist alpha-methyldopa (alpha-MD) was then bilaterally implanted in the MPOA or VMAR of 28-day-old females. Evaluation of the gonadotrophin-inhibiting effect of OB on days 30-31 showed that medial preoptic, but not hypothalamic implants of alpha-MD reduced the sensitivity to the inhibitory action of OB. It is proposed that diminution of the dopaminergic activity in the MPOA may play a role in the prepubertal desensitization to the negative oestrogen feedback in female rats.
mesh_terms: D000818:Animals; D002369:Castration; D002784:Cholesterol / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology*; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000502:physiology*; D005246:Feedback; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood; D008750:Methyldopa / Q000494:pharmacology; D011301:Preoptic Area / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D004967:Estrogens; D004958:Estradiol; D008750:Methyldopa; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D002784:Cholesterol; D004298:Dopamine