The proposed project will study the influence of hormones upon reproductive behavior and the morphology of neurons which mediate that behavior, by focusing upon a simple neuromuscular system in adult male rats. Motoneurons in the spinal nucleus of the bulbocavernosus (SNB) innervate the striated perineal muscle bulbocavernosus (BC). The BC is active during copulation and aids in the formation and removal of cervical plugs which are crucial for reproductive success in this species. The BC is also active during penile flips that can be mediated by the isolated spinal cord. Androgen manipulations in adulthood alter both the reflexes and several neuroanatomical measures of the SNB, including soma size, nuclear size and dendritic extent. Experiments will be conducted to determine which cellular population(s) interact with androgen in order to alter neural morphology. These experiments include local application of androgen and the manipulation of systemic androgen levels after isolation of various components of the SNB system. Only after the primary site of androgen action is ascertained can further experiments be performed to understand the cellular mechanisms behind these changes in neural structure and behavior. The project will also investigate the ways in which various afferent inputs to the SNB alter its structure and function. These experiments will include pharmacological manipulation of oxytocin receptors, anatomical determination of brain afferents to the SNB motoneurons, and varying copulatory experience. These studies should provide further understanding of reproductive behaviors and the means by which hormones can alter behavior. Furthermore, by studying the mechanisms of neural plasticity, one can gain a greater understanding of learning and memory processes.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
Project #
Application #
Study Section
Biopsychology Study Section (BPO)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California Berkeley
Schools of Arts and Sciences
United States
Zip Code
Breedlove, S Marc (2017) Prenatal Influences on Human Sexual Orientation: Expectations versus Data. Arch Sex Behav 46:1583-1592
Pfau, Daniel R; Hobbs, Nicholas J; Breedlove, S Marc et al. (2016) Sex and laterality differences in medial amygdala neurons and astrocytes of adult mice. J Comp Neurol 524:2492-502
Oki, Kentaro; Halievski, Katherine; Vicente, Laura et al. (2015) Contractile dysfunction in muscle may underlie androgen-dependent motor dysfunction in spinal bulbar muscular atrophy. J Appl Physiol (1985) 118:941-52
Halievski, Katherine; Henley, Casey L; Domino, Laurel et al. (2015) Androgen-dependent loss of muscle BDNF mRNA in two mouse models of SBMA. Exp Neurol 269:224-32
Puts, David A; Pope, Lauramarie E; Hill, Alexander K et al. (2015) Fulfilling desire: evidence for negative feedback between men's testosterone, sociosexual psychology, and sexual partner number. Horm Behav 70:14-21
Renier, Kayla J; Troxell-Smith, Sandra M; Johansen, Jamie A et al. (2014) Antiandrogen flutamide protects male mice from androgen-dependent toxicity in three models of spinal bulbar muscular atrophy. Endocrinology 155:2624-34
Chen, Chieh V; Brummet, Jennifer L; Lonstein, Joseph S et al. (2014) New knockout model confirms a role for androgen receptors in regulating anxiety-like behaviors and HPA response in mice. Horm Behav 65:211-8
Johnson, Ryan T; Breedlove, S Marc; Jordan, Cynthia L (2013) Androgen receptors mediate masculinization of astrocytes in the rat posterodorsal medial amygdala during puberty. J Comp Neurol 521:2298-309
Culbert, Kristen M; Breedlove, S Marc; Sisk, Cheryl L et al. (2013) The emergence of sex differences in risk for disordered eating attitudes during puberty: a role for prenatal testosterone exposure. J Abnorm Psychol 122:420-32
Johnson, Ryan T; Schneider, Amanda; DonCarlos, Lydia L et al. (2012) Astrocytes in the rat medial amygdala are responsive to adult androgens. J Comp Neurol 520:2531-44

Showing the most recent 10 out of 54 publications