Fig. 2.

Confocal projections of MOR immunoreactivity in the MPN of ovariectomized rats that were treated with 2 μg of estradiol benzoate followed by either oil vehicle (EB) or 500 μg of progesterone (EB + P) 26 hr later and were killed 30 hr after the initial treatment (Experiment II) or received a microinfusion of either ENDO-1 (50 nmol) or aCSF into the lateral ventricle (Experiment V). The resulting images illustrate that both EB- and ENDO-1-treated animals had an internalized pattern of MOR immunoreactivity (arrows). In EB + P- and aCSF-treated rats, MOR immunoreactivity was associated with the plasma membrane (arrowheads), indicating that these receptors were not activated. Scale bar, 10 μm.