Evidence in favour of a direct input from the ventromedial nucleus to gonadotropin-releasing hormone neurones in the ewe : an anterograde tracing study

International audienc

Estrogen receptor expression in brainstem noradrenergic neurons of the sheep

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Estrogen receptor expression in brainstem noradrenergic neurons of the sheep

International audienc

Localization of estrogen-receptive neurons projecting to the GnRH neuron-containing rostral preoptic area of the ewe

International audienc

Fluctuating Estrogen and Progesterone Receptor Expression in Brainstem Norepinephrine Neurons through the Rat Estrous Cycle

Norepinephrine (NE) neurons within the nucleus tractus solitarii (NTS; A2 neurons) and ventrolateral medulla (A1 neurons) represent gonadal steroid-dependent components of several neural networks regulating reproduction. Previous studies have shown that both A1 and A2 neurons express estrogen receptors (ERs). Using double labeling immunocytochemistry we report here that substantial numbers of NE neurons located within the NTS express progesterone receptor (PR) immunoreactivity, whereas few PRs are found in ventrolateral medulla. The evaluation of ERα and PR immunoreactivity in NE neurons through the estrous cycle revealed a fluctuating pattern of expression for both receptors within the NTS. The percentage of A2 neurons expressing PR immunoreactivity was low on metestrus and diestrus (3-7%), but increased significantly to approximately 24% on proestrous morning and remained at intermediate levels until estrus. The pattern of ERα immunoreactivity in A2 neurons was more variable, but a similar increment from 11% to 40% of NE neurons expressing ERα was found from diestrus to proestrus. Experiments in ovariectomized, estrogen-treated and estrogen-plus progesterone-treated rats revealed that PR immunoreactivity in A2 neurons was induced strongly by estrogen treatment, whereas progesterone had no significant effect. The numbers of ERα-positive NE neurons were not influenced by steroid treatment. These observations provide direct evidence for PRs in NE neurons of the brainstem and show that cyclical patterns of gonadal steroid receptor expression exist in A2, but not A1, neurons through the rat estrous cycle. The expression of PR in A2 neurons appears to be driven principally by circulating estrogen concentrations. The fluctuating levels of ERα and PR expression in these brainstem NE neurons may help generate cyclical patterns of biosynthetic and electrical activity within reproductive neural networks

Identification of neurokinin B-expressing neurons as an highly estrogen-receptive, sexually dimorphic cell group in the ovine arcuate nucleus

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Immunohistochemical evidence for the presence of various kisspeptin isoforms in the mammalian brain

Kisspeptins are small peptides encoded by the Kiss1 gene that have been the focus of intense neuroendocrine research during the last decade. Kisspeptin is now considered to have important roles in the regulation of puberty onset and adult estrogen-dependent feedback mechanisms on gonadotrophin releasing hormone secretion. Several kisspeptin antibodies have been generated that have enabled an overall view of kisspeptin peptide distribution in the brain of many mammalian species. However, it remains that the distribution of the different kisspeptin isoforms is unclear in the mammalian brain. Here we report on two new N terminal-directed kisspeptin antibodies, one against the mouse Kisspeptin-52 sequence (AC053) and one against the rat Kisspeptin-52 sequence (AC067) and use them to specifically map these long isoforms in the brains of mouse and rat respectively. Kisspeptin-52 immunoreactivity was detected in the two main kisspeptin neuronal populations of the rostral periventricular area and arcuate nucleus but not in the dorsomedial hypothahamus. A large number of fibres throughout the ventral forebrain were also labelled with these two antibodies. Finally, comparison with the most commonly used C terminal-directed kisspeptin antibodies further suggests the presence of shorter kisspeptin fragments in the brain with specific inter- and intracellular expression patterns