[Abstract Title]. - Society for Neuroscience

Poster
279. Steroids and Plasticity I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 279.9/MM23
Topic: E.01.c. Steroids and plasticity
Support: NIH Grant DA08259
NIH-MSTP Grant GM07739
Title: Sex differences in the level and subcellular distribution of delta-opioid receptor
immunoreactivity in hippocampal principal cells
Authors: *T. J. WILLIAMS 1,2 , A. TORRES-REVERON 1 , T. A. MILNER 1,3 ;
1 Neurol and Neurosci, Weill Cornell Med. Coll, New York, NY; 2 Weill
Cornell/Rockefeller/Sloan-Kettering Tri-Institutional MD-PhD Program, New York, NY; 3 Lab.
of Neuroendocrinology, The Rockefeller Univ., New York, NY
Abstract: Our previous studies revealed that ovarian steroids influence endogenous opioid
peptide levels and trafficking of mu-opioid receptors (MORs) in the rat hippocampal formation
(HF). However, whether ovarian steroids affect the levels or trafficking of delta opioid receptors
(DORs) in the HF is unknown. Here, the brains of proestrus (as assessed by vaginal smear
cytology) female, diestrus female, and male adult (2-3 month old) Sprague-Dawley rats were
perfusion fixed with paraformaldehyde and acrolein. Vibratome cut coronal sections through the
HF were processed for quantitative immuno-peroxidase light microscopy or immuno-gold
electron microscopy using antisera directed against the DOR (Chemicon, rabbit polyclonal;
Cheng et al., 1995, guinea pig polyclonal). Consistent with previous studies in males (Commons
and Milner 1996, 1997), DOR-immunoreactivity (-ir) localized to select interneurons and
principal cells in the female HF. Light microscopic densitometry analysis, performed by
hippocampal region using NIH Image, revealed that in comparison to males, proestrus (high
estrogen) females display reduced DOR-ir in the CA1 pyramidal cell layer while diestrus
females show reduced DOR-ir in the dentate granule cell layer. No differences were observed
between males and females within CA1 or dentate hilar interneurons. Electron microscopic
analysis showed reduced total DOR labeling per dendrite and reduced localization of DORs to
the dendritic plasmalemma within CA1 stratum radiatum in females (regardless of estrous phase)
compared to males. Further analysis suggested that diestrus females had reduced total DOR per
dendrite while proestrus females exhibited decreased plasmalemmal distribution of DORs.
Postsynaptic DOR activation is thought to increase potassium conductance and hyperpolarize
membranes. Thus, proestrus females, with fewer plasmalemmal DORs available for ligand