Neuropeptides are involved in numerous brain activities being responsible for a wide spectrum of higher mental functions. The purpose of this concise, structural and qualitative investigation was to map the possible immunoreactivity of the novel regulatory peptides: spexin (SPX) and nesfatin-1 within the human claustrum. SPX is a newly identified peptide, a natural ligand for the galanin receptors (GALR) 2/3, with no molecular structure similarities to currently known regulatory factors. SPX seems to have multiple physiological functions, with an involvement in reproduction and food-intake regulation recently revealed in animal studies. Nesfatin-1, a second pleiotropic neuropeptide, which is a derivative of the nucleobindin-2 (NUCB-2) protein, is characterized by a wide distribution in the brain. Nesfatin-1 is a substance with a strong anorexigenic effect, playing an important role in the neuronal circuits of the hypothalamus that regulate food intake and energy homeostasis. On the other hand, nesfatin-1 may be involved in several important brain functions such as sleep, reproductive behaviour, cognitive processes, stress responses and anxiety. For the first time we detected and described a population of nesfatin-1 and SPX expressing neurons in the human claustrum using immunohistochemical and fluorescent methods. The study presents the novel identification of SPX and nesfatin-1 immunopositive neurons in the human claustrum and their assemblies show similar patterns of distribution in the whole structure.

Department of Anatomy Faculty of Medical Sciences in Katowice Medical University of Silesia ul Medyków 18 40 752 Katowice Poland

Department of Histology Faculty of Medical Sciences in Katowice Medical University of Silesia ul Medyków 18 40 752 Katowice Poland

Division of Biomedical and Life Sciences Faculty of Health and Medicine Lancaster University Lancaster LA1 4YG UK

Institute for Environmental Studies Faculty of Science Charles University Benatska 2 12801 Prague Czechia

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