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Identification of suprachiasmatic melanotrope‐inhibiting neurons in Xenopus laevis : A confocal laser‐scanning microscopy study
Author(s) -
Ubink R.,
Tuinhof R.,
Roubos E.W.
Publication year - 1998
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19980720)397:1<60::aid-cne5>3.0.co;2-g
Subject(s) - pars intermedia , biology , endocrinology , suprachiasmatic nucleus , medicine , glutamate decarboxylase , xenopus , retrograde tracing , neuropeptide y receptor , dopaminergic , pituitary gland , dopamine , central nervous system , neuropeptide , biochemistry , enzyme , hormone , receptor , gene
The amphibian Xenopus laevis is able to adjust its skin color to the light intensity of the environment. Paling of the skin is achieved by inhibiting the release of α‐melanophore‐stimulating hormone (α‐MSH) from the melanotrope cells in the pars intermedia of the pituitary gland. The release of α‐MSH is inhibited by γ‐aminobutyric acid (GABA), neuropeptide Y (NPY), and dopamine (DA). To locate and identify neurons that might be responsible for the inhibitory input, double and triple immunocytochemistry, retrograde tracing from the pars intermedia with the carbocyanine membrane probe 1,1′dilinoleyl‐3,3,3′,3′‐tetramethylindocarbocyanine, 4‐chlorobenzene‐sulfonate (Fast DiI), and confocal laser‐scanning microscopy were combined. Glutamic acid decarboxylase (GAD), tyrosine hydroxylase (TH), and NPY were found to coexist in an axonal network innervating the pars intermedia. The suprachiasmatic nucleus (SC) contained different populations of neurons that were single, double, or triple labelled for GAD, NPY, and TH. In the lateral SC, NPY + neurons were observed. TH‐immunoreactive (TH‐IR) neurons occurred in the medial, dorsolateral, lateral, and ventrolateral SC. Neurons that were double labelled for NPY and TH and triple labelled for Fast DiI, NPY, and TH were present in the ventrolateral SC. This same area contained neurons that were triple labelled for GAD, NPY, and TH. It is concluded that the triple‐labelled and probably the double‐labelled ventrolateral SC neurons (suprachiasmatic melanotrope‐inhibiting neurons) innervate the pituitary pars intermedia and are responsible for the NPY‐, DA‐, and GABA‐mediated inhibition of melanotrope cell activity in Xenopus laevis . J. Comp. Neurol. 397:60–68, 1998. © 1998 Wiley‐Liss, Inc.