Summary: Pregnancy and lactation trigger major physiological changes, including shifts in body temperature and environmental preferences. Researchers have now discovered that postpartum female mice develop a long-term preference for cooler environments, driven by brain changes.
These changes involve a specific group of neurons in the preoptic area (POA) that express estrogen receptor alpha (ERα). Postpartum mice showed reduced warm sensitivity and increased cold sensitivity in these neurons, helping explain their new thermal preferences.
Key Facts:
- Temperature Shift: Postpartum mice preferred cooler environments for over four weeks after weaning.
- Brain Mechanism Identified: The shift was linked to reduced activity of ERα-expressing neurons in the preoptic area.
- Reproductive Experience Impact: Deleting estrogen receptors in these neurons in virgin females mimicked postpartum behavior.
Source: Baylor College of Medicine
Mothers experience major metabolic adaptations during pregnancy and lactation to support the development and growth of the new life. Although many metabolic changes have been studied, body temperature regulation and environmental temperature preference during and after pregnancy remain poorly understood.
Researchers at Baylor College of Medicine and collaborating institutions show in the journal Molecular Metabolism that postpartum female mice develop new environmental temperature preferences and reveal brain changes mediating these changes.
“In both humans and mice, body temperature increases during early pregnancy, drops to normal temperature during late pregnancy and then goes up again during lactation,” said co-corresponding author Dr. Chunmei Wang, assistant professor of pediatrics at USDA/ARS Children’s Nutrition Research Center at Baylor.
In this study, Wang and her colleagues investigated what changes occurred in the brain that mediated the new temperature preference.
“We worked with mice and found that female mice prefer a cooler environment starting from late pregnancy and persisting in long-term postpartum,” Wang said.
“For more than four weeks post-weaning female mice had a lower body temperature and preferred cooler environments; they lost their typical preference for warm environments (30 °C/86 °F) but still avoided cold environments (15 °C/59 °F).”
To identify the biological underpinnings of these changes, the researchers studied the preoptic area (POA), a brain region important for sensing and regulating body temperature.
“We discovered that the change in temperature preference in postpartum female mice was associated with a significant decrease in a particular group of neurons, estrogen receptor alpha (ERα)-expressing neurons in the preoptic area of the brain (ERαPOA neurons),” Wang said.
Supporting this finding, the researchers found that virgin females in which the estrogen receptor alpha had been deleted in ERαPOA neurons also preferred lower temperatures and avoided warmer locations, mimicking postpartum females.
Looking closely into the ERαPOA neurons, the researchers found that these neurons vary in their ability to sense warm or cold temperatures – one group of ERαPOA neurons can directly respond to warmth, while another group responds to cooler temperatures.
“Interestingly, compared to female mice that had not been pregnant, ERαPOA neurons of postpartum females had reduced response to warmth and an enhanced response to cold,” Wang said.
Together, the results support that the ability of ERαPOA neurons to sense warmth and cold is regulated by reproductive experience and leads to changes in temperature preferences that alter the animal’s warmth-seeking behavior.
Currently, the researchers are exploring the function of each group of ERαPOA neurons on the regulation body temperature and thermal preference.
Other contributors to this work include Nan Zhang, Meng Yu, Qianru Zhao, Bing Feng, Yue Deng, Jonathan C. Bean, Qingzhuo Liu, Benjamin P. Eappen, Yang He, Kristine M. Conde, Hailan Liu, Yongjie Yang, Longlong Tu, Mengjie Wang, Yongxiang Li, Na Yin, Hesong Liu, Junying Han, Darah Ave Threat, Nathan Xu, Taylor Smiley, Pingwen Xu, Lulu Chen and co-corresponding authors Tianshu Zeng and Yanlin He. The authors are affiliated with one or more of the following institutions: Baylor College of Medicine, Huazhong University of Science and Technology, Hubei Branch of National Center for Clinical Medical Research of Metabolic Diseases, Louisiana State University, South-central Minzu University and the University of Illinois.
Funding: This work was supported by grants from the USDA/CRIS (3092-51000-062-04(B)S), Pennington Biomedical Research Center institutional funding and the National Natural Science Foundation of China.
About this neuroscience research news
Author: Taylor Barnes
Source: Baylor College of Medicine
Contact: Taylor Barnes – Baylor College of Medicine
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Altered thermal preference by preoptic estrogen receptor alpha neurons in postpartum females” by Chunmei Wang et al. Molecular Metabolism
Abstract
Altered thermal preference by preoptic estrogen receptor alpha neurons in postpartum females
Objective
This study aims to investigate how reproductive experience (RE) alters thermal preference and thermoregulation in female mice, with a focus on estrogen receptor alpha (ERα)-expressing neurons in the preoptic area (POA).
Methods
Thermal preference and body temperature were measured in female mice with and without RE, and virgin female mice with selective deletion of ERα from the POA (ERαPOA-KO). The number and activity of ERα-expressing POA neurons (ERαPOA) were assessed using immunohistochemistry and in vitro electrophysiology in response to temperature changes and ERα agonist.
Results
We showed that female mice prefer a cooler environment starting from late pregnancy and persisting long term postpartum. Female mice with RE (>4 weeks post-weaning) displayed lower body temperature and a lower thermal preferred temperature, and lost preference for warm environments (30 °C) but preserved avoidance of cold environments (15 °C).
This was associated with a significant decrease in the number of ERαPOA neurons. Importantly, virgin female ERαPOA-KO mice displayed lower thermal preferred temperature and impaired warm preference, mimicking RE mice. We further found that distinct ERαPOA subpopulations can be regulated by temperature changes with or without presynaptic blockers, and by ERα agonist.
More importantly, RE decreased the number of warm-activated ERαPOA neurons and reduced the excitatory effects of warmth and estrogen-ERα signaling, while cold-activated ERαPOA neurons were slightly enhanced in female mice with RE.
Conclusion
Our results support that the thermosensing ability and estrogenic effects in ERαPOA neurons are regulated by reproductive experience, altering thermal preference.
