{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T02:48:20Z","timestamp":1788922100778,"version":"build-2803163510"},"reference-count":54,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2025,8,18]],"date-time":"2025-08-18T00:00:00Z","timestamp":1755475200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Medical Science Council at the Medical University of Sofia","award":["D-126\/29.05.2024"],"award-info":[{"award-number":["D-126\/29.05.2024"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>The bed nucleus of the stria terminalis (BNST) is a heterogeneous and complex limbic forebrain structure, which plays an important role in drug addiction and anxiety. Dynorphin and kappa-opioid receptors (DYN\/KOR) comprise a crucial neural system involved in modulating stress-induced drug and alcohol addiction. Previous studies have highlighted the BNST as a brain region with a strong DYN\/KOR expression. However, no research has been conducted on the adolescent plasticity of this system. In the present study, we used 20- and 60-day-old Wistar rats to reveal the adolescent dynamics and possible sex differences of the DYN\/KOR system in certain BNST nuclei associated with addiction behavior. We found a low expression of DYN in neuronal perikarya and a significant increase in DYN-containing nerve fibers in the lateral posterior and lateral dorsal nuclei of the rat BNST. In addition, an enhanced expression of KORs was observed in the examined BNST subnuclei with some sex differences favoring females, thus highlighting the importance of considering critical developmental differences between sexes in research. The dynamics of the DYN\/KOR system observed in this study may help to explain the increased vulnerability of adolescents for developing drug and alcohol addiction.<\/jats:p>","DOI":"10.3390\/ijms26167955","type":"journal-article","created":{"date-parts":[[2025,8,18]],"date-time":"2025-08-18T16:22:33Z","timestamp":1755534153000},"page":"7955","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Expression of Dynorphin and Kappa-Opioid Receptors in the Bed Nucleus of the Stria Terminalis: Focus on Adolescent Development"],"prefix":"10.3390","volume":"26","author":[{"given":"Albert R.","family":"Gradev","sequence":"first","affiliation":[{"name":"Department of Anatomy and Histology, Medical University of Sofia, 1431 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pavel I.","family":"Rashev","sequence":"additional","affiliation":[{"name":"Institute of Biology and Immunology of Reproduction \u201cAcad. Kiril Bratanov\u201d, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1745-7755","authenticated-orcid":false,"given":"Dimitrinka Y.","family":"Atanasova","sequence":"additional","affiliation":[{"name":"Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria"},{"name":"Department of Anatomy, Faculty of Medicine, Trakia University, 6003 Stara Zagora, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Angel D.","family":"Dandov","sequence":"additional","affiliation":[{"name":"Department of Anatomy and Histology, Medical University of Sofia, 1431 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3420-4346","authenticated-orcid":false,"given":"Nikolai E.","family":"Lazarov","sequence":"additional","affiliation":[{"name":"Department of Anatomy and Histology, Medical University of Sofia, 1431 Sofia, Bulgaria"},{"name":"Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,8,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"166","DOI":"10.1038\/s41386-018-0125-6","article-title":"Sex differences in neural mechanisms mediating reward and addiction","volume":"44","author":"Becker","year":"2019","journal-title":"Neuropsychopharmacology"},{"key":"ref_2","unstructured":"Paxinos, G. 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