Sexually dimorphic expression of calcitonin gene-related peptide (CGRP) immunoreactivity by rat mediobasal hypothalamic neurons

Abstract

Although the hypothalamic arcuate nucleus is a sexually dimorphic region of the rat brain, there are no reports of sex differences in the number of neurons containing specific neuropeptides within this structure. As cells synthesizing calcitonin gene-related peptide (CGRP) have been shown to exhibit sex differences in other steroid-receptive regions of the rat brain, we examined whether the CGRP-immunoreactive cells located in the mediobasal hypothalamus may also be sexually dimorphic. Immunostaining of sections from male and female colchicine-treated rats revealed a small population of CGRP-immunoreactive cells distributed throughout the arcuate nucleus. Immunoreactive cells were also detected in the lateral hypothalamic perifornical region, dorsomedial, posterior periventricular and ventral tuberomammillary nuclei, and zona incerta. Cell count analysis revealed approximately twice as many CGRP-immunoreactive cell profiles in the rostral (P < 0.01), middle (P < 0.001), and caudal (P < 0.01) thirds of the arcuate nucleus of male rats compared with females. A significant sex difference in immunoreactive cell numbers (male > female) was also detected within the caudal dorsomedial nucleus (P < 0.05) but not in the posterior periventricular nucleus, perifornical region and zona incerta. Although fibers immunoreactive for CGRP were identified in low density throughout the mediobasal hypothalamus, only female rats displayed prominent fiber staining in the periventricular region. Double-labelling immunofluorescence experiments revealed that the CGRP-immunoreactive cells within the zona incerta, but not the hypothalamus, were also immunoreactive for tyrosine hydroxylase; at least 60% of the A13 dopaminergic neurons co-express CGRP. These results provide evidence that sex differences exist in the number of specific neuropeptide-synthesizing cells within the hypothalamic arcuate nucleus and provide further examples of cell populations expressing CGRP immunoreactivity in a sexually dimorphic manner.

Gestational Exposure to Sodium Valproate Disrupts Fasciculation of the Mesotelencephalic Dopaminergic Tract, With a Selective Reduction of Dopaminergic Output From the Ventral Tegmental Area

“…This would indicate that the development of this cell group may not have been completed by E13.5, i.e., the time of VPA administration. Notably, the TH+ cells of the latter region are of mixed catecholaminergic type, e.g., about 60% of the TH+ neurons coexpress calcitonin in A13 (Leclercq and Herbison, 1996), meaning that the effect of VPA may not be confined to the purely dopaminergic phenotype of ventral mesencephalic (VM) neurons.…”

A study of the central injection effects of chrysin on behavioural and intra hypothalamic gene expression levels of CRH and CGRP in male rats

“…The CGRP is synthesized throughout the central nervous system. In addition to the spinal cord, brainstem and other parts of the brain, the CGRP is expressed in the different nuclei of the hypothalamus including the arcuate nucleus, lateral hypothalamic and medial basal of the hypothalamus in males and females (Leclercq et al 1996). It has been found that the central injection of CGRP activates the brain areas related to stress while antagonism of CGRP receptors suppresses the anxiogenic behaviors (Sink et al 2011;Rahman et al 2023) Chrysin, a natural polyphenol from the avonoid group, is a bioactive constituent of honey, propolis, and several herbal medicinal herbs such as Passi ora incarnate, Passi ora coerulea, and Oroxylum indicum (Talebi et al 2021).…”