Inhibition of luteinizing hormone secretion by localized administration of estrogen, but not dihydrotestosterone, is enhanced in the ventromedial hypothalamus during feed restriction in the young wether

Biol Reprod. 2005 Oct;73(4):781-9. doi: 10.1095/biolreprod.105.042275. Epub 2005 Jun 22.

Abstract

The ability of steroids to inhibit LH secretion is enhanced during undernutrition. To identify potential hypothalamic sites at which this enhancement may occur, we examined LH secretion in feed-restricted or fed young wethers treated with locally administered metabolites of testosterone. In experiment 1, microimplants containing crystalline estradiol-17beta (E) or cholesterol were administered via chronic guide tubes directed to the preoptic area (POA) or ventromedial hypothalamus (VMH) in fed or feed-restricted wethers. E treatment in the VMH decreased LH pulse frequency, pulse amplitude, and mean LH concentration in feed-restricted, but not fed, wethers. E may act in the POA to suppress LH under feed restriction, but definite conclusions cannot be drawn because of steroid-independent effects of feed restriction on LH pulse frequency. In experiment 2, the effect of dihydrotestosterone (DHT) in the VMH was determined. DHT administration to the VMH did not alter LH secretion in either feed-restricted or fed wethers. Thus the VMH is one site wherein E negative feedback is enhanced during feed restriction in the wether. In contrast, we found no evidence for enhanced responsiveness to androgen negative feedback within the VMH of feed-restricted wethers. We suggest that increased sensitivity within the VMH to E, but not to DHT, is important for suppressing LH secretion in undernourished male sheep.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Diet
  • Dihydrotestosterone / administration & dosage
  • Dihydrotestosterone / pharmacology*
  • Dopamine Antagonists / pharmacology
  • Drug Implants
  • Estradiol / administration & dosage
  • Estradiol / pharmacology*
  • Luteinizing Hormone / drug effects
  • Luteinizing Hormone / metabolism*
  • Male
  • Orchiectomy
  • Preoptic Area / drug effects
  • Preoptic Area / metabolism
  • Sheep
  • Sulpiride / pharmacology
  • Ventromedial Hypothalamic Nucleus / drug effects
  • Ventromedial Hypothalamic Nucleus / metabolism*

Substances

  • Dopamine Antagonists
  • Drug Implants
  • Dihydrotestosterone
  • Estradiol
  • Sulpiride
  • Luteinizing Hormone