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BioMed Research International
Volume 2015, Article ID 364746, 8 pages
http://dx.doi.org/10.1155/2015/364746
Research Article

The Type 7 Serotonin Receptor, 5-HT7, Is Essential in the Mammary Gland for Regulation of Mammary Epithelial Structure and Function

1Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, OH 45267, USA
2Center for Regenerative and Developmental Biology, Tufts University, Medford, MA 02155, USA
3Department of Dairy Science, University of Wisconsin-Madison, Madison, WI 53706, USA
4Department of Natural Sciences, Asbury University, Wilmore, KY 40390, USA

Received 10 September 2014; Revised 19 December 2014; Accepted 21 December 2014

Academic Editor: Yun Yen

Copyright © 2015 Vaibhav P. Pai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Autocrine-paracrine activity of serotonin (5-hydroxytryptamine, 5-HT) is a crucial homeostatic parameter in mammary gland development during lactation and involution. Published studies suggested that the 5-HT7 receptor type was important for mediating several effects of 5-HT in the mammary epithelium. Here, using 5-HT7 receptor-null (HT7KO) mice we attempt to understand the role of this receptor in mediating 5-HT actions within the mammary gland. We demonstrate for the first time that HT7KO dams are inefficient at sustaining their pups. Histologically, the HT7KO mammary epithelium shows a significant deviation from the normal secretory epithelium in morphological architecture, reduced secretory vesicles, and numerous multinucleated epithelial cells with atypically displaced nuclei, during lactation. Mammary epithelial cells in HT7KO dams also display an inability to transition from lactation to involution as normally seen by transition from a columnar to a squamous cell configuration, along with alveolar cell apoptosis and cell shedding. Our results show that 5-HT7 is required for multiple actions of 5-HT in the mammary glands including core functions that contribute to changes in cell shape and cell turnover, as well as specialized secretory functions. Understanding these actions may provide new interventions to improve lactation performance and treat diseases such as mastitis and breast cancer.