Endocrine Abstracts

Orexin-A are newly described family of orexigenic hypothalamic neuropeptides. The distribution of orexin immunoreactive fibers overlaps with the LHRH neuronal system in the septo-preoptic area and the arcuate nucleus-median eminence region. However, the actual role of the orexinergic system in the timing of puberty onset remains unexplored. The aim of the present study was to assess, in immature female and male rats, the effect of the orexinergic system on the reproductive axis and on pubertal development. With this purpose we evaluated the effects of chronic central administration of orexin-A peptide on puberty onset. I.c.v. administration of orexin-A in the lateral cerebral ventricle was conducted in unanaesthetised 30-day-old female rats and 35-day-old male rats. Our results show that the activation of the orexinergic system during postnatal days and provide novel evidence for a role of the orexinergic system as a downstream element in the hypothalamic network triggering the onset of puberty. Consequently, we suggest that orexin-A is a metabolic cue necessary for the acquisition of reproductive maturity, although its functional role and the site(s) and timing of its action(s) relative to the phase of pubertal development are still questions.