Characterisation and origins of melanin-concentrating hormone immunoreactive fibres of the posterior lobe of the pituitary and median eminence during lactation in the Long-Evans rat.
J Neuroendocrinol
; 31(9): e12723, 2019 09.
Article
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| MEDLINE
| ID: mdl-31034718
ABSTRACT
Although the melanin-concentrating hormone (MCH) and its coding mRNA are predominantly found in the tuberal hypothalamus, there is detectable synthesis of MCH in the preoptic hypothalamus exclusively in lactating dams, suggesting a participation of MCH in the alterations that take place after parturition. Also implicated in the dam physiology is oxytocin, a neurohormone released from the posterior pituitary that is necessary for milk ejection. Because the projection fields from oxytocin-immunoreactive (-IR) neurones and the mediobasal preoptic hypothalamus overlap and MCH-IR neurones are found in proximity to oxytocin neurones, we investigated the spatial relationship between MCH and oxytocin fibres. Accordingly, we employed multiple immunohistochemistry labelling for MCH and oxytocin for light and electron microscopy techniques, in addition to i.v. tracer injection combined with in situ hybridisation to identify MCH neurones that project to neurosecretory areas. As described for other strains, lactating Long-Evans dams also display immunoreactivity for MCH in the preoptic hypothalamus on days 12 and 19 of lactation. The appearance of these neurones is contemporaneous with an increase in MCH-IR fibres in both the internal layer of the median eminence and the posterior pituitary. In both regions, MCH- and oxytocin-IR fibres were found in great proximity, although there was no evidence for synaptic interaction between these two populations at the ultrastructural level. The tracer injection revealed that only mediobasal preoptic MCH neurones project to the posterior pituitary, suggesting a neuroendocrine-modulatory role for this population. When taken together, the results obtained in the present study indicate that neuroplasticity events at the mediobasal preoptic hypothalamus that occur during late lactation may be part of a neuroendocrinology control loop involving both MCH and oxytocin.
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Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Hipófisis
/
Hormonas Hipofisarias
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Hormonas Hipotalámicas
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Eminencia Media
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Melaninas
Límite:
Animals
Idioma:
En
Revista:
J Neuroendocrinol
Asunto de la revista:
ENDOCRINOLOGIA
/
NEUROLOGIA
Año:
2019
Tipo del documento:
Article
País de afiliación:
Brasil