Colocalization of estrogen receptor β (ERβ) with spinally projecting and vasopressinergic neurons in the hypothalamic paraventricular nucleus (PVN) during pregnancy

Abstract

Spinally projecting neurons in the rostral ventrolateral medulla (RVLM) and the PVN are sympathoexcitatory. The PVN contributes to increased sympathetic nerve activity in near‐term pregnant (P) compared to nonpregnant rats (NP). ERβ is highly expressed in RVLM‐projecting PVN neurons in male and female rats, but little is known about ERβ expression in PVN neurons in pregnancy. Immunohistochemistry was used to evaluate colocalization of ERβ with spinally projecting (retrograde tracer = fluorogold, FG) and vasopressin (AVP) cells in the PVN (−1.8 and −2.12 mm caudal to bregma) in 6 NP and 6 P female rats. Total number of AVP (primarily posterior magnocellular region) and FG labeled cells was similar in NP and P, while ERβ cells tended (P = 0.12) to be higher in NP. Total % co‐labeling with ERβ was greater in spinally projecting compared to AVP cells in both NP (33 ± 4 vs 21± 8%) and P rats (31 ± 4 vs.3 ± 8%). The number of both spinally projecting and ERβ immunoreactive cells was greater in the ventrolateral parvocellular (vlp) compared to the dorsal parvocellular subregion of the PVN in both P and NP rats. Although in the vlp the number of FG‐ERβ co‐labeled cells was greater in NP (27± 5) than P (16± 3) rats, the % of spinally projecting cells expressing ERβ was not different ( NP = 48 ±9% ; P =48 ±9%). We conclude that changes in ERβ expression alone cannot explain increased PVN mediated sympathoexcitation in P rats. NIH R01 HL091164 (CMH)