Neuroendocrine control by dopamine of teleost reproduction

Abstract

While gonadotropin-releasing hormone (GnRH) is considered as the major hypothalamic factor controlling pituitary gonadotrophins in mammals and most other vertebrates, its stimulatory actions may be opposed by the potent inhibitory actions of dopamine (DA) in teleosts. This dual neuroendocrine control of reproduction by GnRH and DA has been demonstrated in various, but not all, adult teleosts, where DA participates in an inhibitory role in the neuroendocrine regulation of the last steps of gametogenesis (final oocyte maturation and ovulation in females and spermiation in males). This has major implications for inducing spawning in aquaculture. In addition, DA may also play an inhibitory role during the early steps of gametogenesis in some teleost species, and thus interact with GnRH in the control of puberty. Various neuroanatomical investigations have shown that DA neurones responsible for the inhibitory control of reproduction originate in a specific nucleus of the preoptic area (NPOav) and project directly to the region of the pituitary where gonadotrophic cells are located. Pharmacological studies showed that the inhibitory effects of DA on pituitary gonadotrophin production are mediated by DA-D2 type receptors. DA-D2 receptors have now been sequenced in several teleosts, and the coexistence of several DA-D2 subtypes has been demonstrated in a few species. Hypophysiotropic DA activity varies with development and reproductive cycle and probably is controlled by environmental cues as well as endogenous signals. Sex steroids have been shown to regulate dopaminergic systems in several teleost species, affecting both DA synthesis and DA-D2 receptor expression. This demonstrates that sex steroid feedbacks target DA hypophysiotropic system, as well as the other components of the brain-pituitary gonadotrophic axis, GnRH and gonadotrophins. Recent studies have revealed that melatonin modulates the activity of DA systems in some teleosts, making the melatonin-DA pathway a prominent relay between environmental cues and control of reproduction. The recruitment of DA neurons for the neuroendocrine control of reproduction provides an additional brain pathway for the integration of various internal and environmental cues. The plasticity of the DA neuroendocrine role observed in teleosts may have contributed to their large diversity of reproductive cycles.

Hormonally modulated migraine is associated with single-nucleotide polymorphisms within genes involved in dopamine metabolism

“…In rats, catechol estrogens decrease the turnover rate of dopamine in the corpus striatum [48]. Also, animal studies have shown that dopamine influences GnRH production at the level of the hypothalamus [49][50][51][52]. In fact, in vitro data suggest that dopamine can stimulate GnRH secretion from the human hypothalamus [53].…”

Effects of climate change on fish reproduction and early life history stages

“…This begins with hypothalamic synthesis and synaptic release of peptide gonadotropin-releasing hormones (GnRH) onto the gonadotropic cells of the pituitary gland, where they stimulate the synthesis and release of the protein hormones, follicle-stimulating hormone (FSH) and luteinising hormone (LH) (reviewed in Planas and Swanson 2008;LevaviSivan et al 2010;Zohar et al 2010). In many species, there is also inhibitory tone imposed by the action of dopamine (DA)-secreting neurones, with the release of FSH and LH being dependent on the balance between GnRH stimulation and DA inhibition (reviewed in Dufour et al 2010). The GnRH-pituitary interaction is further modulated by melatonin produced by the light-sensitive pineal gland by as-yet poorly understood mechanisms (reviewed in Migaud et al 2010), by the kisspeptin system through direct effects on the activity of GnRH-producing neurones (reviewed in Akazome et al 2010) and by the feedback effects of gonadal steroids (reviewed in Pankhurst 2008).…”

Catecholaminergic connectivity to the inner ear, central auditory, and vocal motor circuitry in the plainfin midshipman fish porichthys notatus

“…Teleosts exhibit CA neuronal populations and innervation patterns in nuclei with proposed homologies to those found in tetrapods where they are known to modulate motivated social and reproductive behavior (Goodson and Kingsbury, 2013;Petersen et al, 2013). However, aside from DA neurons in the anterior preoptic area that are well documented to regulate the hypothalamic-pituitary-gonadal (HPG) axis in teleosts (Dufour et al, 2010;Dufour et al, 2005;Kah et al, 1987;Peter and Fryer, 1983), the function of specific CA cell groups in teleosts are largely unknown. However, recent studies in teleosts have begun to characterize cFos induction of CA nuclei to social challenge stimuli (O'Connell et al, 2013;Petersen et al, 2013).…”