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Increased Fos Expression in Preoptic Calcitonin Gene‐Related Peptide (CGRP) Neurones following Mating but not the Luteinizing Hormone Surge in Female Rats
Author(s) -
Herbison Allan E.,
King Ian S.,
Tan Keith K. C.,
Dye Sandra
Publication year - 1995
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1995.tb00772.x
Subject(s) - medicine , endocrinology , luteinizing hormone , preoptic area , ovariectomized rat , hypothalamus , biology , estrogen , calcitonin , gonadotropin releasing hormone , hormone , kisspeptin , lordosis behavior , estradiol benzoate
The functional relationship between sexually dimorphic neural populations and sex differences in reproductive functioning is unclear. The present study has investigated the function of the sexually dimorphic, estrogen‐receptive, calcitonin gene‐related peptide (CGRP) neurones in the female preoptic area by examining patterns of Fos immunoreactivity within these cells in relation to the luteinizing hormone surge and lordosis behaviour. In the first experiment, ovariectomized rats were treated with estradiol alone or estradiol plus progesterone to induce the luteinizing hormone surge. The percentage of CGRP neurones with Fos‐positive nuclei was not different in estradiol alone (18 ± 4%) and estradiol/progesterone‐treated (24 ± 3%) rats although the number of Fos‐immunoreactive cells in the medial preoptic nucleus was increased 2‐fold (P<0.01) in estrogen/progesterone‐treated rats and 40 ± 5% of luteinizing hormone‐releasing hormone neurones were found to express Fos in this group. In the second experiment, ovariectomized rats were treated with estradiol and progesterone and either, mated with a single male or placed in an empty cage, for 30 min. The number of Fos‐immunoreactive cells in the medial preoptic nucleus was increased 4‐fold in mated rats (P<0.01) and the percentage of CGRP neurones with Fos‐positive nuclei increased from 24 ± 3% to 38 ± 2% (P<0.01) in mated animals. No differences were detected in the number of luteinizing hormone‐releasing hormone neurones with Fos‐positive nuclei in mated and non‐mated animals. These results suggest that a sub‐population of CGRP neurones in the medial preoptic nucleus may express Fos on a constitutive basis in steroid‐treated animals and that, while not altered in relation to the luteinizing hormone surge, Fos expression by these cells is increased following mating. Although the precise role of these CGRP neurones has yet to be ascertained, the present experiments provide direct evidence of a functional relationship between a specific sexually dimorphic neural population and a component of sexually differentiated reproductive functioning.