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The neuropeptide control of gonadotropin secretion at the level of the anterior pituitary gland is primarily through the stimulatory action of the hypothalamic decapeptide, gonadotropin-releasing hormone (GnRH), which was originally isolated from mammals and subsequently from non-mammals. To date, however, an inhibitory peptide of gonadotropin release is(More)
Successful reproduction requires maintenance of the reproductive axis within fine operating limits through negative feedback actions of sex steroids. Despite the importance of this homeostatic process, our understanding of the neural loci, pathways, and neurochemicals responsible remain incomplete. Here, we reveal a neuropeptidergic pathway that directly(More)
The neuropeptide control of gonadotropin secretion is primarily through the stimulatory action of the hypothalamic decapeptide, GnRH. We recently identified a novel hypothalamic dodecapeptide with a C-terminal LeuPro-Leu-Arg-Phe-NH2 sequence in the domestic bird, Japanese quail (Coturnix japonica). This novel peptide inhibited gonadotropin release in vitro(More)
Little information is available for neurosteroidogenesis in the central nervous system (CNS) of lower vertebrates. Therefore, in the present study, we examined the enzymatic activity and localization of 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4-isomerase (3betaHSD), a key steroidogenic enzyme, in the CNS of adult male zebrafish to clarify central(More)
Gonadotropin-releasing hormone (GnRH) regulates reproduction in all vertebrates. Until recently, an antagonistic neuropeptide for gonadotropin was unknown. The discovery of an RFamide peptide in quail that inhibits gonadotropin release in vitro raised the possibility of direct hypothalamic inhibition of gonadotropin release. This peptide has now been named(More)
We previously isolated a novel dodecapeptide containing a C-terminal -Arg-Phe-NH(2) sequence, SIKPSAYLPLRF-NH(2) (RFamide peptide), from the quail brain. This quail RFamide peptide was shown to decrease gonadotropin release from the cultured anterior pituitary and to be located at least in the quail hypothalamo-hypophysial system. We therefore designated(More)
De novo steroidogenesis from cholesterol is a conserved property of vertebrate brains, and such steroids synthesized de novo in the brain are called neurosteroids. The identification of neurosteroidogenic cells is essential to the understanding of the physiological role of neurosteroids in the brain. We have demonstrated recently that neuronal(More)
Neurosteroids are de novo synthesized in the nervous system through mechanisms at least partly independent of peripheral steroidogenic glands. However, the concept of neurosteroidogenesis in neurons is not clear in mammalian brains. The present study identified the presence of cytochrome P450scc in the rat Purkinje cell, a typical cerebellar neuron.(More)
Gonadotropin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that inhibits gonadotropin secretion in birds and mammals. To further understand its physiological roles in mammalian reproduction, we identified its precursor cDNA and endogenous mature peptides in the Siberian hamster brain. The Siberian hamster GnIH precursor cDNA encoded two(More)
Neurosteroids are synthesized de novo in the brain and the cerebellar Purkinje cell is a major site for neurosteroid formation. We have demonstrated that the rat Purkinje cell actively produces progesterone de novo from cholesterol only during neonatal life and progesterone promotes dendritic growth, spinogenesis and synaptogenesis via its nuclear receptor(More)