Quantitation of prolactin receptor mRNA in the maternal rat brain during pregnancy and lactation.
Prolactin receptor (PRL-R) expression in the brain is increased in lactating rats compared with non-pregnant animals. The aim of the present study was to determine the time-course of changes in PRL-R mRNA levels during pregnancy and/or lactation, and to determine relative levels of the two forms (short and/or long form) of receptor mRNA in specific brain regions. Brains were collected from female rats on dioestrus, days 7, 14 or 21 of pregnancy, day 7 of lactation or day 7 post-weaning. Frozen, coronal sections were cut (300 microm) and specific hypothalamic nuclei and the choroid plexus were microdissected using a punch technique. Total RNA was extracted and reverse transcribed, then first strand cDNA was amplified using quantitative real-time PCR. Results showed an up-regulation of long-form PRL-R mRNA in the choroid plexus by day 7 of pregnancy compared with dioestrus, which further increased on days 14 and 21 of pregnancy and day 7 of lactation, and then decreased to dioestrous levels on day 7 post-weaning. Short-form PRL-R mRNA levels increased on day 14 of pregnancy relative to dioestrus, increased further on day 7 of lactation and decreased on day 7 post-weaning. Changes in mRNA were reflected in increased levels of PRL-R immunoreactivity in the choroid plexus during pregnancy and lactation, compared with dioestrus. In the arcuate nucleus, long-form PRL-R mRNA was increased during pregnancy. In contrast to earlier work, no significant changes in short- or long-form PRL-R mRNA expression were detected in several other hypothalamic nuclei, suggesting that changes in hypothalamic mRNA levels may not be as marked as previously thought. The up-regulation of PRL-R mRNA and protein expression in the choroid plexus during pregnancy and lactation suggest a possible mechanism whereby increasing levels of peripheral prolactin during pregnancy may have access to the central nervous system. Together with expression of long-form PRL-R mRNA in specific hypothalamic nuclei, these results support a role for prolactin in regulating neuroendocrine and behavioural adaptations in the maternal brain.
Augustine
R A
RA
Department of Anatomy and Structural Biology, School of Medical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand.
Kokay
I C
IC
Andrews
Z B
ZB
Ladyman
S R
SR
Grattan
D R
DR
D000818:Animals; D017931:DNA Primers; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology; D007774:Lactation / Q000502:physiology*; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011388:Prolactin / Q000502:physiology; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011981:Receptors, Prolactin / Q000235:genetics*; D014158:Transcription, Genetic
D017931:DNA Primers; D020033:Protein Isoforms; D012333:RNA, Messenger; D011981:Receptors, Prolactin; D011388:Prolactin