Cellular neuroscienceSexual dimorphism in the organization of the rat hypothalamic infundibular area
Section snippets
Experimental procedures
Preparation of brain tissue, immunocytochemical procedures and controls, were as detailed (Ciofi, 2000). All efforts were made to minimize the number of animals used and their suffering. They were anesthetized (xylazine/ketamine: 2 mg/5 mg per 100 g b.w.), operated on and killed (after an overdose of 20% chloral hydrate) in accordance with the European Communities Council Directive of 24 November 1986 (86/609/EEC). Experiments conformed to guidelines of the Comité Régional d’Ethique Aquitaine
Sexually dimorphic distribution of NKB-LI axons in the infundibular area
Throughout the rostro-caudal extent of the ARC, both sexes displayed NKB-LI perikarya in similar number and distribution and a “shared NKB-LI innervation” (more intensely labeled in females). In addition, “sex-specific” NKB-LI innervations were conspicuous (Fig. 1, Fig. 2, Fig. 3, Fig. 4). In females, more NKB-LI axonal courses with perisomatic arrangements were apparent in the vmARC/sub-ependymal zone of the ME while only isolated NKB-LI axons reached the ME external zone. In males,
Discussion
These observations suggest that the infundibular area is qualitatively different in organization between sexes. This evidence may allow progress in understanding how the hypothalamus shapes pituitary pulsatility and integrates humoral feedback: it is discriminative and concerns a region with known structure–function relationships. However, this conclusion is based on visualization of chemical phenotypes instead of true anatomical structure. Also, such a dimorphic anatomical wiring may be
Conclusion
This evidence of a qualitative sex dimorphism in the macro-organization of the hypothalamic interface with both the pituitary and the periphery makes it a privileged site of generation of the male-to-female differences in the adult pattern of pulsatile hormonal secretions. Many other neuronal systems certainly participate in the sex-specific wiring of the hypothalamus. They may not all display such a clear-cut phenotype as NKB neurons here in the rat.
Acknowledgments
We are grateful to Dr. Robert H. Edwards (Univ. California, San Francisco) for his kind gift of antiserum to VGluT2, and to Dr. Vincent Prévot (Inserm U816, Lille, France) for reading the manuscript. Supported by Inserm, La Fondation pour la Recherche Médicale and Université Victor Ségalen Bordeaux 2.
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2022, Pharmacology and TherapeuticsCitation Excerpt :There is thus a unique population of infundibular (human) /arcuate (other species) neurons, which co-express all three neuropeptides, and are referred to as KNDy (Kisspeptin-Neurokinin B-Dynorphin) neurons (Goodman et al., 2007). KNDy neurons form direct contact with both GnRH cell bodies and dendrites in the preoptic area and the mediobasal hypothalamus and project to the median eminence (Ciofi et al., 2006; Clarkson & Herbison, 2006; Dahl, Amstalden, Coolen, Fitzgerald, & Lehman, 2009; Krajewski et al., 2005; Ramaswamy et al., 2008) (Fig. 1). The arcuate KNDy neuronal network is reciprocally interconnected, allowing for the synergistic neuroactivity of interlinked KNDy cells (Burke et al., 2006; Foradori et al., 2002; Lehman, Coolen, & Goodman, 2010).
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