Sex hormone receptors are expressed in identified respiratory motoneurons in male and female rats

Sex hormones including estrogen, progesterone and testosterone can influence breathing. However, it is not clear whether such hormones exert their effects directly on respiratory motoneurons. We used immunocytochemistry to demonstrate that estrogen receptor alpha, estrogen receptor 0 and androgen receptor are localized in respiratory motor neurons. Motoneurons in the hypoglossal (XII) and the phrenic nuclei were retrogradely labeled from the tongue and the diaphragm respectively. Double-label fluorescence immunocytochernistry was used to show that sex hormone receptors are present in respiratory motoneurons of both male and female rats. These data suggest that in male and female rats, sex hormones can modulate the output of respiratory motoneurons directly. (C) 2005 IBRO. Published by Elsevier Ltd. All rights reserved.