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Developmental Biology - Maternal Health
'Maternal Instinct' Is Real
Cells active in an area of female mouse brains — are not active in the same area of male mouse brains...
Research led by biologist Ryoichi Teruyama PhD and students at Louisiana State University (LSU) has identified a group of cells activated by oxytocin in a brain area of female mice — are not present in the same brain area of male mice. Now identified, these cells can be followed and measured as they relate to maternal behavior to be observed in future research.
Oxytocin is widely referred to as the love hormone, playing an important role in regulating social and maternal behavior. In recent years, the oxytocin system has received tremendous attention as key to new treatments for many mental health disorders, such as anxiety, autism spectrum disorders and postpartum depression.
"Many researchers have attempted to investigate the difference between the oxytocin system in females versus males, but no one has successfully found conclusive evidence until now. Our discovery was a big surprise," explains Ryoichi Teruyama PhD, associate professor, department of biological sciences, LSU and leader of the study published in PLOS ONE.
Oxytocin receptor cells are present in the posterior pituitary area of the brain, thought to be involved in regulation of maternal behavior. Expression (function) by oxytocin receptors in these cells only occurs when estrogen is also present, which implies they may induce what we identify as maternal behavior. This newest observation confirms what many recent human studies have also shown — a connection exists between altered expression (function) of oxytocin receptors and postpartum depression.
Postpartum depression contributes to poor maternal health and can have negative affects on child development. A number of studies have found that children of depressed mothers are at risk for a wide range of cognitive, emotional, behavioral and medical problems. Postpartum depression is a major public health concern affecting about 10 to 20 percent of women following childbirth.
The discovery opens doors to potential new treatment and possible drug development for postpartum depression targeting oxytocin receptors.
"I think our discovery could be universal to all mammals, including humans, exhibiting maternal behavior," adds Teruyama.
Student Researchers
Ryan LeBlanc, undergraduate student researcher at LSU, was instrumental to the discovery having taken on the tedious task of marking thousands of oxytocin receptor cells with a red pen. His personal experience building plastic battleship models may have been just the skill set needed preparing for this task.
Doctoral candidate Kaustubh Sharma from Nepal is first author and validated LeBlanc's findings. Sharma continues to investigate how oxytocin receptor cells regulate maternal behavior in female mice.
Abstract
Oxytocin is involved in the regulation of social behaviors including parental behaviors in a variety of species. Oxytocin triggers social behaviors by binding to oxytocin receptors (OXTRs) in various parts of the brain. OXTRs are present in the preoptic area (POA) where hormone-sensitive sexually dimorphic nuclei exist. The present study was conducted to examine whether sex differences exist in the distribution of neurons expressing OXTRs in the POA. Using OXTR-Venus (an enhanced variant of yellow fluorescent protein) mice, the distribution of OXTR-Venus cells in the POA was compared between sexes. The total number of OXTR-Venus cells in the medial POA (MPOA) was significantly greater in females than in males. No detectable OXTR-Venus cells were observed in the anteroventral periventricular nucleus (AVPV) within the MPOA in most of the brain sections from males. We further examined the total number of OXTR-Venus cells in the AVPV and the rest of the MPOA between the sexes. The total number of OXTR-Venus cells in the AVPV in females (615 ± 43) was significantly greater than that in males (14 ± 2), whereas the total number of OXTR-Venus cells in the rest of the MPOA did not differ significantly between the sexes. Thus, the sexually dimorphic expression of OXTR-Venus specifically occurred in the AVPV, but not in the rest of the MPOA. We also examined whether the expression of OXTR in the AVPV is driven by the female gonadal hormone, estrogen. Immunocytochemistry and single-cell RT-PCR revealed the presence of the estrogen receptor ? in OXTR-Venus cells in the female AVPV. Moreover, ovariectomy resulted in the absence of OXTR-Venus expression in the AVPV, whereas estrogen replacement therapy restored OXTR-Venus expression. These results demonstrate that the expression of OXTR in the AVPV is primarily female specific and estrogen dependent. The presence of the sexually dimorphic expression of OXTR in the AVPV suggests the involvement of OXTR neurons in the AVPV in the regulation of female-specific behavior and/or physiology.
Authors
Kaustubh Sharma, Ryan LeBlanc, Masudul Haque, Katsuhiko Nishimori, Madigan M. Reid and Ryoichi Teruyama.
Acknowledgements
The authors thank Dr. J.T. Caprio for reading earlier versions of this manuscript, A.C. Rawls and D.N. Ledet for technical assistance, and Dr. R.A. Malbrue for demonstrating how to perform ovariectomy in mice.
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Aug 2 2019 Fetal Timeline Maternal Timeline News
 A Louisiana State University biologist and students, have discovered cells activated by oxytocin in one area of female mouse brains — are not found in the same area of male mouse brains. CREDIT Ryoichi Teruyama, LSU.
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