Date of Graduation

12-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor

Wayne J. Kuenzel

Committee Member

Alexander Jurkevich

Second Committee Member

David L. Kreider

Third Committee Member

Kathryn D. Curtin

Keywords

Agonistic behavior, Arginine vasotocin, Aromatase, Bed nucleus of the pallial commissure, Bed nucleus of the stria terminalis, Gene expression, Male chicken, Medial preoptic area, Sexual behaviors

Abstract

The study aimed to understand the neuronal regulation of male sexual and agonistic behavior in broiler breeders. First, brain structures associated with sexual and agonistic behavior were identified by mapping Fos expression. The ventromedial subnucleus of medial portion of bed nucleus of the stria teriminalis (BSTM2) was specifically activated by male courtship behavior. The medial preoptic nucleus (POM) and lateral septum (SL) were associated with both sexual and agonistic behaviors. The bed nucleus of the pallial commissure (NCPa) and the paraventricular nucleus (PVN) were closely related to stress. Second, Fos-ir neurons were phenotyped by double labeling Fos with aromatase (ARO) and arginine vasotocin (AVT). Male courtship behavior significantly increased co-expressions of ARO+Fos and AVT+Fos in the BSTM2. In the POM, inter-male interactions decreased visible ARO cell counts while the opposite-sex interaction increased co-expression of ARO+Fos. The caudo-lateral POM (clPOM) and caudo-medial POM (cmPOM) were involved in sexual and agonistic behavior, respectively. Immunostaining for AVT, galanin, serotonin and gonadotropin-releasing hormone (GnRH) were compared between aggressive and non-aggressive males to test their behavior functions. Galanin fiber density in the SL was higher in aggressive males than non-aggressive males and galanin-ir cell counts in the BSTM were negatively associated with aggressive behaviors. Density of vasotocinergic fibers in the SL correlated with sexual behavior. Finally, gene expression of estrogen-producing enzyme aromatase, AVT, corticortropin-releasing hormone (CRH) and their receptors were investigated in males of two chicken lines that differed in their Sociality. Social line had higher P450 expression in the rPOM and clPOM, more ESR1 expression in clPOM and more ESR2 in the NCPa. Higher expression of AVPR1A/VT4R in the rPOM, clPOM, BSTM1, BSTM2 and SL1 were found in the Social line than in the aSocial line. In the cmPOM, higher expression of CRHR1 was found in the Social line and interaction with females only reduced the expression in this line of chickens. Highly level of CRH gene expression was revealed in the NCPa, which strongely supported its role in stress responses. In conclusion, the differential expression of neuromodulators (estrogen, AVT) and their receptors in the brain may contribute to variation in sociosexuality in male broilers.

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