Urocortin II increases spontaneous parental behavior in prairie voles (Microtus ochrogaster)

Abstract

Stress and anxiety play a role in many psychological processes including social behavior. The present study examines the effects of urocortin II (UCN II) on spontaneous parental behavior in adult prairie voles (Microtus ochrogaster). UCN II was found to increase passive parental behavior in voles while not affecting any stress-related measures. Delineating the mechanism of this change will aid in our understanding of the regulation of parenting. Keywordscorticotrophin-releasing hormone; urocortin I, II, and III; parenting; monogamy; vole Urocortin (UCN) II, also known as stresscopin-related peptide, is a 38 amino acid member of the mammalian corticotropin-releasing hormone (CRH) peptide family, which also includes CRH, UCN I, and UCN III [1;2]. CRH mainly binds to type 1 CRH receptors (CRH1), while UCN II and III bind primarily to type 2 CRH receptors, and UCN I binds to both (CRH2) [1]. Each of these hormones has distinctive distribution patterns in the central nervous system and the periphery, suggesting each peptide may have distinct behavioral and physiological effects, although all have been associated with anxiety [2][3][4][5]. In general, agonism of CRH1 receptors is posited to be anxiogenic and agonism of CRH2 receptors is posited to be anxiolytic [6]. UCN II, however, has produced mixed results in tests of anxiety. Central administration of UCN II increased anxiety-like behavior when given intracerebroventricularly (ICV) thirty minutes before a plus maze test [7;8]. It also caused increased anxiety when administered by osmotic minipump infusion during a novel object exploration task [9]. However, UCN II minipump administration caused no differences in open field behavior [9]. In another study, ICV UCN II caused no change in plus-maze behavior either ten minutes or one hour postinjection [10]; however, animals tested four hours post-administration showed a decrease in anxiety-like behavior. It is thus possible that the effects of UCN II on anxiety are dependent on the time-course of administration [6], with anxiogenic effects peaking earlier than anxiolytic effects. Administration of the glucocorticoid, dexamethasone, leads to an increase in UCN II mRNA, which has been suggested to mediate anxiolytic functions of UCN II [11]. Effects of CRH2 ligands on other aspects of behavior, particularly social behavior, are thus far little studied, as are the effects of peripheral administration on anxiety and social behaviors.Corresponding author. Address: Department of Psychology, One Shields Ave., University of California, Davis, CA 95616. Phone: 530-754-5890, Fax: 530-752-2087, Email: klbales@ucdavis.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered w...

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