Dynamics of background adaptation in Xenopus laevis: Role of catecholamines and melanophore-stimulating hormone

• Published in: General and comparative endocrinology Vol. 76; no. 1; pp. 19 - 28
• Main Authors: van Zoest, I.D., Heijmen, P.S., Cruijsen, P.M.J.M., Jenks, B.G.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.10.1989; Elsevier
• Subjects: Adaptation, Physiological - drug effects; Adaptation, Physiological - physiology; Animals; Baclofen - pharmacology; Biological and medical sciences; Catecholamines - pharmacology; Catecholamines - physiology; Female; Fundamental and applied biological sciences. Psychology; Hormones and neuropeptides. Regulation; Hypothalamus. Hypophysis. Epiphysis. Urophysis; Male; Melanocyte-Stimulating Hormones - blood; Melanocyte-Stimulating Hormones - pharmacology; Melanocyte-Stimulating Hormones - physiology; Melanophores - drug effects; Melanophores - physiology; Propranolol - pharmacology; Skin Pigmentation - drug effects; Skin Pigmentation - physiology; Vertebrates: endocrinology; Xenopus laevis; Xenopus laevis - physiology; β-»Adrenergic receptor; MSH; Xenopus laevis; Peptide hormone; Amphibia; Salientia; In vitro; Colour vision; In vivo; Vertebrata; Pituitary hormone; Secretion curve; Radioimmunoassay; Pigments; Melanophore; α-MSH; Adaptation
• ISSN: 0016-6480; 1095-6840
• DOI: 10.1016/0016-6480(89)90028-2

The pars intermedia of the pituitary gland in Xenopus laevis secretes α-melanophore-stimulating hormone (α-MSH), which causes dispersion of pigment in dermal melanophores in animals on a black background. In the present study we have determined plasma levels of α-MSH in animals undergoing adaptation to white and black backgrounds. Plasma values of black-adapted animals were high and decreased rapidly after transfer to a white background, as did the degree of pigment dispersion in dermal melanophores. Plasma MSH values of white-adapted animals were below the detection limit of our radioimmunoassay. Transfer of white animals to a black background resulted in complete dispersion of melanophore pigment within a few hours, but plasma MSH levels remained low for at least 24 hr. This discrepancy between plasma MSH and degree of pigment dispersion suggested the involvement of an additional factor for stimulating dispersion. Results of in vitro and in vivo experiments with receptor agonists and antagonists indicated that a β-adrenergic mechanism, functioning at the level of the melanophore, is involved in the stimulation of pigment dispersion during the early stages of background adaptation.