title: Central control of melanotrope cells of Xenopus laevis.
abstract: Our research focusses on the role of brain and hypophysis in the control of background adaptation in the clawed toad, Xenopus laevis. This adaptation is regulated by alpha-melanophorestimulating hormone (alpha-MSH). Previously, it was shown that various neurotransmitters influence alpha-MSH release. Here we report about the origin of these factors. Using retrograde labelling techniques combined with immunocytochemistry, it was found that the inhibitory transmitters dopamine and neuropeptide Y coexist in neurons in the suprachiasmatic nucleus. These neurons project to the pars intermedia and synaptically contact the alpha-MSH-producing melanotrope cells. In the synapses also GABA is present. Tracing of the optic nerve indicated the presence of a direct retinosuprachiasmatic tract. Furthermore, locus coeruleus neurons project to the pars intermedia. They contain the inhibitory transmitter noradrenaline. The stimulatory factors corticotropin-releasing hormone and thyrotropin stimulating hormone originate from the magnocellular nucleus which send its processes to the neural lobe of the hypophysis.
authors: Department of Cellular Animal Physiology, University of Nijmegen, The Netherlands.
authors: R
authors: R
authors: Tuinhof
authors: A
authors: A
authors: González
authors: W J
authors: WJ
authors: Smeets
authors: W J
authors: WJ
authors: Scheenen
authors: E W
authors: EW
authors: Roubos
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001921:Brain / Q000502:physiology*; D004298:Dopamine / Q000502:physiology; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D009474:Neurons / Q000502:physiology; D009478:Neuropeptide Y / Q000502:physiology; D010902:Pituitary Gland / Q000166:cytology / Q000502:physiology*; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000502:physiology; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: D009478:Neuropeptide Y; D009074:Melanocyte-Stimulating Hormones; D004298:Dopamine