Seasonal control of reproduction is critical for the perpetuation of species living in temperate zones that display major changes in climatic environment and availability of food resources. In mammals, seasonal cues are mainly provided by the annual change in the 24-h light/dark ratio (i.e., photoperiod), which is translated into the nocturnal production of the pineal hormone melatonin. The ann...

OBJECTIVES In the hypothalamus, kisspeptin and RFamide-related peptide (RFRP) regulate gonadotropin-releasing hormone expression. Kisspeptin and RFRP are also found in the testes and might play roles in steroidogenesis and spermatogenesis. DESIGN AND RESULTS The present study demonstrated that the hypothalamic mRNA expression level of the kisspeptin receptor was decreased by the injection of ...

Recent work has led to the hypothesis that kisspeptin/neurokinin B/dynorphin (KNDy) neurons in the arcuate nucleus (ARC) play a key role in gonadotropin-releasing hormone (GnRH) pulse generation and gonadal steroid feedback, with kisspeptin driving GnRH release and neurokinin B and dynorphin acting as pulse start and stop signals, respectively. A separate cell group, expressing RFamide-related ...

Seasonally breeding mammals rely on the photoperiodic signal to restrict their fertility to a certain time of the year. The photoperiodic information is translated in the brain via the pineal hormone melatonin, and it is now well-established that it is the variation in the duration of the nocturnal peak of melatonin which synchronizes reproduction with the seasons. The Syrian hamster is a long ...

In this article we develop the theory of residually finite rationally p (RFRp) groups, where p is a prime. We first prove a series of results about the structure of finitely generated RFRp groups (either for a single prime p, or for infinitely many primes), including torsion-freeness, a Tits alternative, and a restriction on the BNS invariant. Furthermore, we show that many groups which occur n...

Jerboas are wild rodents exhibiting exceptional adaptation to their desert environment. Under harsh autumn conditions, they shut down reproduction, increase body weight and hibernate, while during spring they become sexually active even under negative energy-balance. We recently reported that these rhythms are associated with synchronized changes in genes expressing reproductive (Kiss1, Rfrp) a...

The subjective experience of stress leads to reproductive dysfunction in many species, including rodents and humans. Stress effects on reproduction result from multilevel interactions between the hormonal stress response system, i.e., the hypothalamic-pituitary-adrenal (HPA) axis, and the hormonal reproductive system, i.e., the hypothalamic-pituitary-gonadal (HPG) axis. A novel negative regulat...

The existence of a hypothalamic gonadotropin-inhibiting system has been elusive. A neuropeptide named gonadotropin-inhibitory hormone (GnIH, SIKPSAYLPLRF-NH(2)) which directly inhibits gonadotropin synthesis and release from the pituitary was recently identified in quail hypothalamus. Here we identify GnIH homologs in the human hypothalamus and characterize their distribution and biological act...

Gonadotrophin-inhibitory hormone (GnIH) is a novel hypothalamic neuropeptide that was discovered in birds as an inhibitory factor for gonadotrophin release. RFamide-related peptide (RFRP) is a mammalian GnIH orthologue that inhibits gonadotrophin synthesis and release in mammals through actions on gonadotrophin-releasing hormone (GnRH) neurones and gonadotrophs, mediated via the GnIH receptor (...

BACKGROUND RFamide-related peptide-3 (RFRP-3) inhibits gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) secretion in rats. This study evaluates the effects of litter size and suckling intensity on RFRP mRNA expression in the dorsomedial hypothalamic nucleus (DMH) of rats. MATERIALS AND METHODS A total of 32 pregnant and 4 non-lactating ovariectomized (control group) Sprague-...