Immunohistochemical mapping of pro-opiomelanocortin- and pro-dynorphin-derived peptides in the alpaca (Lama pacos) diencephalon

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Manso B.
Sánchez M.L.
Medina L.E.
Aguilar L.A.
Díaz-Cabiale Z.
Narváez J.A.
Coveñas R.
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Using an indirect immunoperoxidase technique, we studied the distribution of cell bodies and fibres containing non-opioid peptides (adrenocorticotropin hormone (ACTH), alpha-melanocyte-stimulating hormone) and opioid peptides (beta-endorphin (1–27), alpha-neo-endorphin, leucine-enkephalin) in the alpaca diencephalon. No immunoreactive cell bodies containing ACTH were found. Perikarya containing the other four peptides were observed exclusively in the hypothalamus and their distribution was restricted. Perikarya containing alpha-melanocyte-stimulating hormone or alpha-neo-endorphin showed a more widespread distribution than those containing leucine-enkephalin or beta-endorphin (1–27). Cell bodies containing pro-opiomelanocortin-derived peptides were observed in the arcuate nucleus, anterior and lateral hypothalamic areas and in the ventromedial and supraoptic hypothalamic nuclei, whereas perikarya containing alpha-neo-endorphin (a pro-dynorphin-derived peptide) were found in the arcuate nucleus, dorsal and lateral hypothalamic areas, and in the paraventricular, ventromedial and supraoptic hypothalamic nuclei. Immunoreactive cell bodies containing leucine-enkephalin were found in the lateral hypothalamic area and in the paraventricular hypothalamic nucleus. Immunoreactive fibres expressing pro-opiomelanocortin-derived peptides were more numerous than those expressing pro-dynorphin-derived peptides. A close anatomical relationship was observed: in all the diencephalic nuclei in which beta-endorphin (1–27)-immunoreactive fibres were found, fibres containing alpha-melanocyte-stimulating hormone or alpha-neo-endorphin were also observed. Fibres containing beta-endorphin (1–27), alpha-melanocyte-stimulating hormone or alpha-neo-endorphin were widely distributed throughout the diencephalon, but fibres containing ACTH or leucine-enkephalin showed a moderate distribution. The distribution of the five peptides studied here is also compared with that reported previously in other mammalian species. The widespread distribution observed indicates that both the pro-dynorphin and the pro-opiomelanocortin systems are involved in multiple physiological actions (e.g., food intake, thermoregulation, neuroendocrine and reproductive mechanisms) in the alpaca diencephalon.
The authors thank Professor Gérard Tramu (University of Bordeaux I, France) for kindly providing the first antisera and N. Skinner (University of Salamanca, Spain) for stylistic revision of the English text. This work has been supported by the Ministerio de Educación y Ciencia (BFU2005-02241/BFI), Spain and the Ministerio de Ciencia e Innovación (BFU2008-03369/BFI), Spain and by the CONCYTEC: PROCYT project 2006, Peru.
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protein precursor, alpha intermedin, alpha neoendorphin, beta endorphin[1-27], corticotropin, leucine enkephalin, proopiomelanocortin, enkephalin, preproenkephalin, proopiomelanocortin, adult, animal, animal experiment