GONADOTROPIN-RELEASING-HORMONE - PRESENT CONCEPTS, FUTURE-DIRECTIONS

There is an overwhelming amount of evidence to indicate that gonadotro pin-releasing hormone (GnRH), a decapeptide, is found in multiple mole cular forms, and is vital for the functional integration of brain-pitu itary-gonadal axis in vertebrates. In simple terms, there is an overal l agreement that GnRH acts as a neuroendocrine regulator of pituitary gonadotropin secretion, gonadal steroid secretion, sexual behavior, an d reproduction. GnRHs are distributed widely within the vertebrate bod y, particularly in the brain. The brain GnRH neuronal system(s) varies in its morphology, ontogenesis and function across vertebrates. It is a highly dynamic structure which does not function at the same level throughout life. A large framework of studies completed to date attest s to the emerging concept that GnRH neuronal system is regulated by a complex neural circuitry, comprised of diverse neurochemical signals, which may provide excitatory or inhibitory input to GnRH neurons. Whil e general considerations on GnRH systems may be similar among vertebra tes, it must not seduce us to generalize the more specific details. In fact, there may occur ontogenesis and reproductive status-related cha nges and a timetable of complex neuroendocrine events that are probabl y (certainly) species-specific.